5 Colon and

Technique Proctography Barium Enema Evacuation proctography, a dynamic imaging modality, evaluates functional and morphologic Contrary to the opinion of some computed abnormalities of the anorectal region. This tomography (CT) and magnetic resonance examination, also called dynamic proctography imaging (MRI) enthusiasts, a double-contrast or , requires specially adopted barium enema continues to be a viable option fluoroscopic equipment, including rapid in a setting of suspected , colorectal filming, that is not available in many radiology cancer screening and detection, and follow-up departments. It has a role in evaluating unex- after therapy. Similarly, it is a sad reflection on plained , incontinence, rectal pro- medical practice that occasionally a statement lapse, and rectal pain. It evaluates the presence still appears in print that barium sulfate is toxic or absence of a sigmoidocele, , rectal to the colon (1). prolapse, puborectalis muscle contraction, anal One of the present indications for a barium canal opening, changes in anorectal angle, and enema is failed colonoscopy, although in some rectal emptying. Resultant findings appear to be centers CT colonography is gaining ground independent of contrast agent viscosity used. and magnetic resonance (MR) virtual colono- Pre- and postproctography questionnaires scopy is on the horizon. An obvious concern by referring clinicians revealed that clinicians in performing any enema shortly after failed found this study of major benefit in 40% and of colonoscopy is risk of perforation. Contrary to moderate benefit in 40% (2); the primary diag- the experience of some investigators, the author nosis was changed in 18% of patients, intended has found barium enemas performed on the surgical management became nonsurgical in same day as colonoscopy to be mostly unsatis- 14%, intended nonsurgical therapy became sur- factory; invariably the patient is “tired out”from gical in 4%, and type of surgery contemplated the colonoscopy, has difficulty cooperating, changed in 10%. excessive colonic spasm is often encountered, Although detailed and precise anatomic and residual fluid interferes with mucosal measurements are possible with this study, their coating. A formal air contrast barium enema, clinical relevance is still not clear. In particular, performed a week or so later, tends to be of the borderland between normal and abnormal superior quality. is poorly defined. Lack of confidence in some

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ADVANCED IMAGING OF THE ABDOMEN of the findings becomes evident after patient colonoscopies are in women.A prior abdominal symptoms persist following surgical correction hysterectomy is associated with a higher rate of of an alleged abnormality. incomplete colonoscopy. Computed tomographic proctography is fea- Complete colonoscopy consists in visualiz- sible, but rarely performed. The study is per- ing cecal landmarks, an elusive task in some formed with the patient seated; coronal images patients. Attempts to provide photographs of aid in outlining perineal floor muscles. Sagittal cecal landmarks have met with limited success. reconstruction allows comparison with conven- Experienced endoscopists display consider- tional proctography. able disparity in deciding whether complete An open configuration MR system allows colonoscopy had been performed when review- image acquisition with the patient in a vertical ing photographs of cecal landmarks (6). position. Anorectal angle changes, The miss rate of colonoscopy was esti- function, puborectalis muscle configuration, mated by performing two consecutive back-to- and pelvic floor dynamics are evaluated at rest back colonoscopies on the same day (7); overall and during straining (3). Even if an open MR polyp miss rate was 24%, being 27% for polyps unit is not available, conventional procto- £5mm, 13% for lesions 6 to 9mm, and 6% for graphy is gradually being replaced by pelvic those ≥1cm. The miss rates for small polyps floor MRI using an endoanal coil. Suspected occurred among essentially all endoscopists. fistulas, sphincter lacerations, rectoceles, tumor Polyp size is routinely estimated by endo- invasion by low rectal carcinomas, and other scopists. Because of endoscopic lens system pelvic floor disorders are imaged in detail limitations, apparent measurements tend to be with this technique. Currently this is considered smaller than actual. Lesions in the periphery of to be the most accurate imaging test of distal the field of view are smaller than in the center. perirectal structures, especially the external Likewise, size varies with depth of view. Com- sphincter. paring magnified radiographic polyp measure- Two approaches are possible for MR rectal ments (which are magnified due to inherent studies: either rectal distention with fluid and focus-object-film geometry) with the minified use of a surface coil or no distention and use of endoscopic appearance results in considerable a rectal MR coil. More studies have addressed discrepancy. the latter technique, but advances in hardware Laser fluorescence spectroscopy performed and software design make it difficult to predict during colonoscopy has detected colonic dys- which path will be superior. One technique con- plasia with a claimed sensitivity and specificity sists of opacifying the rectum with 200mL of an of over 90% (8). ultrasonography (US) gel and obtaining a single sagittal T2-weighted gradient echo sequence Computed Tomographic Colonography through the rectum (4); with a 1.5-T MR unit, a temporal resolution of 1.1 second is obtained, The introduction of multidetector CT opened allowing imaging at rest and during straining possibilities for complex three-dimensional and evacuation. (3D) colon studies, allowing the entire abdomen Using a surface coil in the anal canal, and pelvis to be covered with a slice thickness endorectal MRI appears superior to endorec- of <3mm in under 30 seconds, allowing single tal US in visualizing the external sphincter, breath-hold scanning. An effective slice thick- although internal sphincter lesions are better ness approaching 1mm should, in theory, detect evaluated with endorectal US (5). all relevant polyps. Once lumen distention is introduced, one is well on the road toward CT detection of colon neoplasms. Yet although multiple publications have established the fea- Colonoscopy sibility of screening CT colonography, its role Conventional remains undefined. The terms CT colonography, CT colonoscopy, The prevalence of incomplete colonoscopy and virtual colonoscopy have often been used varies considerably among endoscopists and interchangeably to describe a global examina- institutions, ranging from several percent up to tion designed to detect colonic tumors regard- one third of studies. A majority of incomplete less of specific images obtained. Computed 187

COLON AND RECTUM tomographic colonography appears to better review of supine and prone images significantly describe this procedure, but virtual colonoscopy increase polyp detection sensitivity (10), and is ingrained in the literature, although a trend the trend is to use both positions. has developed to use CT colonography for a Ingestion of oral contrast agents is generally global examination consisting of narrow colli- considered inadequate preparation for CT mation data reconstructed to various combina- cancer detection. In practice, colonic lavage tions of 2D multiplanar reformatting and 3D combined with oral barium contrast for stool images and to limit the term virtual colonoscopy tagging and oral iodinated contrast for elec- to specific colonoscopy-like images.Hydro-CT is tronic fluid marking are useful techniques. A a less often used term to describe colonic dis- viable option consists of oral contrast combined tention with fluid during a CT study. with in frail, elderly patients who do Currently CT colonography is a viable alter- not tolerate more vigorous CT colonography or nate after failed or incomplete conventional a barium enema, realizing that this technique colonoscopy. Residual colonic distention is ade- detects only more bulky tumors. quate in many patients when CT is performed Air is commonly used to distend the lumen. shortly after incomplete colonoscopy, but addi- Carbon dioxide is an alternative agent but tional air insufflation is often helpful. Indica- the relative merits of one over the other are tions for CT colonography have expanded arguable. Adequacy of distention is evaluated considerably and in some centers it has mostly with a CT scout image.With newer CT scanners, replaced conventional colonoscopy for polyp if a study is being performed for suspected detection, leaving the latter modality for colitis, especially , some authors therapy of detected polyps. find little advantage for intraluminal contrast. As an aside, a tap-water enema is often Technique administered if colon visualization is desired during abdominal CT examination. Comparing Although CT colonography is generally water, methylcellulose, and ultrasound gel as regarded as a technically easy study, interpreta- multislice CT rectal contrast agents, methylcel- tion requires a steep learning curve. Data eval- lulose was significantly superior to ultrasound uation time and number of false positive gel in differentiating normal from diseased findings decrease with experience. Similar to a bowel (11); although better rectal distention barium enema, a colon-cleansing regimen is was achieved with methylcellulose and ultra- required with most current CT colonography sound gel, superior more proximal colon dis- techniques. Numerous false positives ensue if tention was obtained with water. Of these residual stool is present, thus emphasizing the three agents, the authors recommend rectal importance of a colon-cleansing regimen, a methylcellulose. difficult task in most practices. One study Computed tomographic colonography with achieved ideal bowel preparation in only 19% of multidetector CT results in significantly 200 patients (9). The two bowel preparations better colonic distention and yields fewer respi- commonly employed are a polyethylene glycol ratory artifacts compared to single-detector CT. electrolyte (“wet”) solution or a phospho-soda Computed tomographic colonography is a (“dry”) preparation, both given the day prior to viable alternate after failed or incomplete con- CT colonography. Polyethylene glycol elec- ventional colonoscopy. A prospective study of trolyte solution results in considerably more patients performed within 2 hours of incom- bowel residual fluid. plete colonoscopy found that although residual Current limitations of CT colonography colonic distention was adequate in most include fluid retention and inadequate luminal patients, additional air insufflation significantly distention due to spasm. Similar to a barium increased colon distention (12). enema, polyps tend to be missed if the lumen is Once patient scanning is completed, the data not distended. Spasm is minimized by judicious are transferred to a workstation for analysis. use of an antispasmodic agent. Problems inher- These are complex examinations, and hundreds ent with fluid retention are partly overcome of images are generated in transverse, multi- by performing the study with the patient both planar reformatted, and 3D endoluminal prone and supine,at the expense of doubling the modes. The relative advantages of axial, coronal, radiation dose. Nevertheless, acquisition and 2D, and 3D display techniques are still evolving; 188

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Figure 5.1. A,B: Two views of three-dimensional (3D) computed tomography (CT) double-contrast virtual colonoscopy. Images can be analyzed from any perspective in space.(Courtesy of Wolfgang Luboldt, M.D., Johann Wolfgang Goethe University, Frankfurt-am- Main.) in some patients several techniques are neces- plays. Experienced abdominal radiologists sary to adequately visualize the entire colonic achieve similar polyp detection rates using 2D wall. A typical practice is to use primarily 2D multiplanar reformation and 3D display tech- multiplanar reformatted imaging for analysis niques (14). Computed tomography colonogra- and reserve 3D imaging for specific problems; phy using axial 2D data and a cine mode and 3D endoluminal views appear necessary to differ- “fly-through” with surface-rendered and multi- entiate polyps from folds. Several commercial planar reformatted images identified the same 3D endoluminal volume rendering and naviga- number of polyps with both techniques (15). A tional systems are available and further metaanalysis of reported accuracy of CT improvements are to be expected. Adding color colonography found a pooled per-patient sensi- (translucency rendering) to 3D aids in ruling tivity for polyps >10mm to be 88%, for polyps out false polyps (13). Interpretation of 2D 6–9mm 84% and for polyps 5 mm or smaller images is faster; on the other hand, navigation 65% (16); per-polyp sensitivity for polyps with 3D endoluminal imaging mimics the con- >10mm was 81%. ventional colonoscopic appearance (Fig. 5.1). A CT colonoscopy perforation rates are low and panoramic view perpendicular to the centerline should be similar to those with a barium enema. is also feasible, with sequential panoramic video Rectal perforation is a potential complication views scanning the colon surface. with blind air insufflation in a setting of more proximal rectosigmoid obstruction. Results Future Studies Polyp detection sensitivity varies depending on scanning and image reconstruction parameters Attempts to circumvent a colon cleansing employed and on polyp size. No consensus regimen are theoretically feasible by tagging exists on preferred viewing modes. For larger colonic content with ingested barium sulfate, polyps a panoramic display results in greater with subsequent digital subtraction of this sensitivity than a virtual endoluminal display material. In patients with suspected or known and 3D displays are more sensitive than 2D dis- colonic polyps, sensitivity for identifying 189

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A

Figure 5.2. Computer-aided polyp detection. A,B: Focal increased tumor perfusion after IV contrast can be automated to “detect” potential neoplasms (arrow). (Courtesy of Wolfgang Luboldt, M.D., Johann Wolfgang Goethe University, Frankfurt-am-Main.)

patients with polyps 1cm or larger was 80% to Magnetic Resonance Colonography 100% if these patients ingested multiple dilute contrast doses over a prior 48 hours (17). Similar to CT colonography, MR colonography Using signal processing of CT colonography is feasible, with relative advantages of CT versus data to identify tumors protruding into bowel MR colonography still evolving. Two broad lumen, an automated polyp detection algorithm approaches are possible: achieved a 64% sensitivity for detecting polyps 10mm or greater (18). Another approach is to 1. Bright lumen MR colonography relies on use tumor contrast enhancement superimposed colon filling with a paramagnetic contrast- on a virtual double contrast and endoscopic water enema and T1-weighted gradient- display (19) (Fig. 5.2). Shape-based polyp detec- recalled echo (GRE) single breath-hold tion and polyp edge enhancement are helpful in acquisition,which results in a hyperintense identifying polyps. luminal image, with other tissues being Teleradiology of CT colonography using hypointense. Multiplanar reformatted 3D wavelet compression to 1:1, 10:1, and 20:1 images and virtual colonoscopic images ratios detected all lesions >10mm for all com- are then obtained. pression ratios, but sensitivities for smaller 2. Dark lumen MR colonography obtained lesions fell off with increasing compression by colon filling with a tap-water enema, ratios (20). which is hypointense on T1-weighted GRE A claimed advantage of CT colonography imaging and an intravenous paramagnetic is that extracolonic abnormalities are also contrast agent to produce a hyperintense detected. Among consecutive patients undergo- colonic wall. A variant technique is to use ing CT colonography, important extracolonic gas or air to distend the lumen; gas has no findings in 11% led to further imaging studies, signal. and as a result several patients underwent surgery (21). Nevertheless, being designed for Another technique consists of colonic disten- optimal colonic imaging, CT colonography is tion with fluid and use of T2-weighted spin echo limited in evaluating solid organs (compared to (SE) imaging. The colon is studied both in cross a fine-tuned CT study of a specific organ or section and using a virtual intraluminal outline. abnormality in question). Often a coronal plane is useful. 190

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Figure 5.3. A,B: Two 3D double-contrast MR virtual colonoscopy images. Visualization is similar to that obtained with CT (see Fig. 5.1). (Courtesy of Wolfgang Luboldt, M.D., Johann Wolfgang Goethe University, Frankfurt-am-Main.)

The disadvantages of the bright lumen tech- and rotated around its axis for detailed study nique include retained air bubbles, which mimic from different planes (Fig. 5.3). polyps. Therefore, both prone and supine views Some authors use the term hydro-MRI when are necessary. Surface-rendered MR virtual a water, saline, or some other contrast enema is colonoscopic views, orthogonal sections and administered prior to MRI. Such an approach is water-sensitive single-shot fast spin echo (FSE) helpful when the study is performed primarily MR images in patients (post–gadolinium-water for suspected colonic disease, and it is a step enema) achieved a 93% sensitivity and 99% toward formal MR colonography. Confusing the specificity in detecting tumors >10mm (22). To issue is that hydro-MRI is also used by some illustrate the complexity of these studies, they authors if oral water or contrast is ingested prior often require instillation of a gadolinium-water to a MR small bowel study.Thus the type of con- enema, prone and supine positioning, breath- trast (including water and air) and route of hold 3D spoiled gradient recalled echo (SGRE) administration need to be specified. The term sequences and also 2D images pre– and double-contrast MR imaging is used by some post–intravenous contrast,and,wherever neces- when both an MR contrast enema and an MR sary, virtual intraluminal images. intravenous (IV) contrast agent are employed. Comparing manganese chloride, iron glyc- Due to its ambiguity, it is probably best avoided. erophosphate, and gadolinium-based enemas A typical technique for colon neoplasms for use in T1 shortening 3D GRE MR colonog- consists of breath-hold T2-weighted half- raphy, the contrast-to-noise ratios for the iron Fourier acquisition single-shot turbo spin echo enema were highest (23); the authors suggest (HASTE) and gadolinium-enhanced breath- replacing gadolinium with iron due to cost hold fat-suppressed T1-weighted SGE images considerations. (25); inflammatory changes appear best on Using a gadopentetate-water enema and the gadolinium-enhanced breath-hold fat- breath-hold 3D SGE sequences, a virtual suppressed T1-weighted SGE images. double-contrast display is achieved by calculat- Air bubbles with the dark lumen technique ing signal intensity differences between adja- are hypointense and blend into the surrounding cent voxels and making adjacent voxels with hypointense water; thus only one patient posi- similar intensities lucent while adjacent voxels tion is necessary, resulting in a shorter scan with different intensities are made opaque (24); time. Likewise, polyps enhance with IV contrast the resultant colonic display can be magnified and stool does not. Potentially, the dark lumen 191

COLON AND RECTUM technique is also useful to evaluate colitis Endovaginal US evaluates the rectum and because of bowel wall enhancement. adjacent structures, including puborectalis Using lumen distention with CO2,breath-hold muscle thickness, sphincter thickness, and single-shot FSE MRI performed during a CO2 sphincter defects. Distending the rectum with a enema in seven patients with known colon car- water enema better delineates perirectal tissue cinoma detected cancers in all and correctly planes. identified tumor extension through muscularis Endorectal US defines surrounding struc- propria in four (26). tures. Urogenital structures and perirectal Colon cleansing is required with most of the spaces are readily imaged. Both proctography above methods. Similar to CT colonography, use and endorectal US evaluate internal and of an oral paramagnetic contrast agents to label external rectal sphincters. Three-dimensional stool (called fecal tagging) in an unprepared endorectal US appears to provide more accurate colon results in stool being hyperintense and control of a biopsy needle toward a perirectal thus blending in with a bright lumen. Or, lesion than is available with other modalities, concentrated oral barium sulfate, which is although the data for this are sparse. The hypointense and thus useful with a dark lumen current primary use of endorectal US is in a technique, is combined with IV gadolinium to setting of rectal cancer and in the workup of enhance the colonic wall and any associated evacuation disorders. tumors (27).These MR stool-tagging techniques Available US miniprobes fit through the are still in their infancy. working channel of an endoscope. Similar to upper gastrointestinal endoscopic US, the role of flexible colonoscopic US in detecting and Ultrasonography staging neoplasms is not yet clear. Compared to other intraabdominal sites, colon Scintigraphy US is rather limited.In some centers it has found a niche in following patients with colonic A gamma camera scintigraphic technique Crohn’s disease but appears less useful with estimates colonic transit, an infrequently used and . Its role in study in clinical practice. pediatric intussusception reduction is well The application of scintigraphy in inflamma- established, less so in adult tumor detection and tory bowel disease and in the bleeding patient is staging. Ultrasonography findings are not covered in each respective section later in this disease-specific. Also, in general, a negative US chapter. Abdominal positron emission tomo- examination does not exclude disease. graphy (PET) scanning is discussed in more Colon US performed after a water enema is detail in Chapter 14. called hydrocolonic sonography (occasionally a methylcellulose-water mixture is used). Hydro- colonic US does detect larger polyps but it is Congenital Abnormalities very operator dependent and has been over- shadowed by CT colonography. Malposition Doppler US evaluates colonic blood flow. Thus viability of an obstructed bowel segment Midgut malrotation is discussed in Chapter 4. is suspected if Doppler US detects no blood The interposition of small or large bowel into flow. Similarly, in inflammatory bowel disease the right subphrenic space, first described by and in acute Doppler flow through Chilaiditi in 1910, is rarely symptomatic and a thickened bowel segment can suggest an acute should be considered a normal variant. Bilateral or ongoing inflammation. bowel interposition is rare (28). Some authors The published terminology is somewhat use the term Chilaiditi’s syndrome to describe inconsistent for US performed with rectal all such bowel interposition; others limit the probes: Endoscopic and endoluminal US include term only to the symptomatic patient. Preva- either a rectal or vaginal probe, whereas the lence of such bowel hepatodiaphragmatic inter- terms transrectal and endorectal US are used position appears to depend on patient position interchangeably. Anorectal echo-endoscopy and and is identified more often with the patient similar terms are also in use. supine. 192

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Detection of bowel interposition is generally neonate are lumped together as low intestinal straightforward with conventional radiography obstructions. and barium studies. The appearance is confus- A microcolon in a neonate is a descriptive ing with US, where interposed bowel loops term of a contrast enema finding rather than a mimic an abnormal mass. Computed tomo- specific disorder and usually suggests distal graphy detects interposition small . Colonic disorders between kidney and psoas muscle (pararenal associated with a small caliber of the entire space) in about 1% (29). Retropsoas interposi- colon include total colonic aganglionosis of tion is slightly more common with the ascend- Hirschsprung’s disease and a microcolon seen ing colon (3%) and (2%) (30); with prematurity. Conventional radiography little retroperitoneal fat favors interposition. A usually differentiates between a high and a low colon interposed posterior to the pancreas, intestinal obstruction. A contrast enema is nec- between the spleen and left hemidiaphragm, is essary to define the obstruction further. rare. Atresia Duplication In rectal atresia the is normal, with the atretic segment located more proximal. No Gastrointestinal duplications are associated bowel fistula is identified. Atresia proximal to with both vertebral and genitourinary tract the rectum is uncommon, although it can occur abnormalities. They occur roughly in one out of anywhere in the colon. Colonic stenosis is rare. 4000 births. Least common are hindgut duplica- A contrast enema reveals a small caliber colon tions. Most are detected in the young. distal to the obstructed, atretic segment. Colonic duplications have either a spherical or tubular appearance, with some long duplica- tions mimicking a second colon lumen. Most of these duplications do not communicate with The most common neonatal colonic obstruction the lumen and occur along the mesenteric is an imperforate anus. Although the term border. Occasionally a duplication contains imperforate anus implies a single and simple noncolonic mucosa, such as heterotopic gastric defect, in reality this is a complex deformity mucosa, small bowel, pancreatic, and even often also involving genitourinary tract struc- respiratory epithelium. The mucosa of some tures and other anomalies. Cryptorchidism is duplications continues secreting and a noncom- common; in general, a more superior level of municating duplication thus increases in size anorectal malformation increases the risk of with time. Imaging identifies an abdominal cryptorchidism. cystic tumor. Rectal atresia differs from an imperforate A rare duplication intussuscepts; it acts as anus. With an imperforate anus the hindgut a source of cecal , or is an incidental does not descend and communicate with the palpable mass at initial presentation. An occa- anus, but either ends blindly or forms a fistula sional one develops a fistula to an adjacent in an abnormal location (ectopic anus). An structure. Magnetic resonance imaging is useful imperforate anus is classified as being high or with the rare rectal duplication in a neonate to low using the puborectalis sling as a dividing show no posterior extension, thus excluding a line. The differentiation between a high and low meningocele. lesion is often made clinically, and imaging plays a limited direct role. The presence of a Obstruction perineal dimple or passage of meconium from the genitourinary tract is a useful guide.In some Common distal ileal obstructions in neonates boys conventional radiography reveals gas in are due to meconium and ileal atresia; in the bladder. the colon obstructions include imperforate The puborectalis muscle tends to be anus, meconium plug syndrome, and hypoplastic with a high obstruction.With a high Hirschsprung’s disease. From a practical view- lesion, the rectum can end blindly, although point, distal ileal and colonic obstructions in the more often in boys it terminates in the posterior 193

COLON AND RECTUM urethra, and less often in the bladder or anterior malformation consisting of communication urethra. In girls the rectum tends to terminate between the urethra and rectum, generally in the vagina. Prior to definitive surgery, most through a single perineal channel. high lesions are treated with a bypass After surgical correction of an anorectal mal- colostomy. The underlying anatomy is then formation—such as rectal pull-through(peri- studied through the distal colostomy limb neoplasty) or posterior sagittal reconstruction (mucous fistula) or, if needed, by cystography (anorectoplasty)—MRI is helpful in detecting and urethrography. complications and to evaluate muscle integrity. A low lesion is usually associated with a per- Residual internal and external sphincter dis- ineal dimple, and no communication exists with ruptions are identified. the genitourinary tract.A variant of a low lesion is a congenital triad consisting of an anorectal malformation, sacral abnormality, and a pre- Megacystis-Microcolon-Intestinal sacral tumor, first described by Currarino et al. Hypoperistalsis Syndrome (31) in 1981 (Table 5.1). Magnetic resonance In the megacystis-microcolon-intestinal hypo- imaging is useful in this triad to detect a syndrome the bladder is markedly tethered cord. distended and a contrast enema shows what ini- Imaging aids in detecting any associated tially looks like a small-caliber colon. Although renal or sacral abnormalities. Magnetic reso- the initial appearance suggests an obstruction, nance imaging outlines the hindgut, bony no mechanical obstruction is found. A short- and muscular pelvic anomalies, including the ened small bowel, at times malrotated, reveals puborectalis muscle and external sphincter, poor or absent peristalsis. Hydronephrosis is and other surrounding anatomy. T1-weighted common. Hydrometrocolpos and segmental images establish whether the puborectalis colonic dilation also occur. Etiology of this rare muscle is hypoplastic. Magnetic resonance autosomal-recessive disorder is unknown. Neu- imaging tends not to identify small fistulous ronal dysplasia is identified in some. This syn- tracts, however, and a contrast study is useful to drome also occurs without megacystis; with define them. such a presentation it blends into the general Some boys have a mix of meconium and category of functional intestinal obstruction in urine and the meconium calcifies; these calcifi- neonates. cations are intraluminal in location, thus distin- The diagnosis should be considered in a guishing them from meconium . Such newborn with a markedly distended bladder a mix of meconium and urine does not occur in and suspected intestinal obstruction. girls with anal atresia; calcified intraluminal content in a girl should suggest a cloacal Meconium Plug Syndrome

Table 5.1. Currarino triad: anorectal malformation, sacral Meconium plug syndrome and small left colon abnormality and presacral mass findings in 11 patients syndrome are probably the same entity. Dia- betes in the mother is common. These full-term Abnormality Number neonates have colonic obstruction due to inspis- Anorectal malformation sated intestinal contents. The colonic lumen is Low imperforate anus 3 narrowed distally and distended proximally. Anorectal stenosis 8 An abrupt transition between dilated and Presacral tumor nondilated bowel is evident in some. Teratoma 7 Hirschsprung’s disease is in the differential Meningocele 2 diagnosis. Dermoid cyst 1 Enteric/dermoid cyst 1 Sacral and other Hirschsprung’s Disease Deformed sacrum 11 Pediatric Tethered cord 2 Hirschsprung’s disease is caused by incomplete Source: Date from Lee et al. (32). caudal migration of neural cells, with bowel 194

ADVANCED IMAGING OF THE ABDOMEN distal to the point of migration arrest constitut- ing an aganglionotic segment. By definition, the aganglionotic segment is continuous and extends to the anus; still, rare patients have seg- mental skip regions. Most often aganglionosis involves the rectum, but occasionally this segment extends more proximally, including the right colon, and the neonate presents with a microcolon. Also uncommon is for agangliono- sis to be limited to the internal sphincter region only. To give an example of the varied involve- ment, in one Central European hospital among 142 children treated for Hirschsprung’s disease, 52% had typical rectal involvement, 30% a long colonic segment, in 13% only a very short rectal segment was involved, and 4% suffered from total colonic aganglionosis (33). For unknown reasons Hirschsprung’s disease is uncommon in prematures. The prevalence in boys is several times greater than in girls. An association exists between multiple endocrine neoplasia (MEN) type IIA and Figure 5.4. Hirschsprung’s disease. Barium enema identifies a Hirschsprung’s disease. Mutations in the RET narrowed rectum (arrows) and a dilated colon more proximally. proto-oncogene are found in both entities (Courtesy of Luann Teschmacher, M.D., University of Rochester.) (patients with MEN type IIB also have colonic abnormalities, including chronic constipation, but any relationship with aganglionosis is not clear). Hirschsprung’s disease is more common in such a setting an allergic colitis should be in patients with Down syndrome. Patients considered in the differential diagnosis. with Ondine’s curse (congenital hypoventilation The usual therapy for established syndrome) and congenital neuroblastoma Hirschsprung’s disease is an initial colostomy, also develop Hirschsprung’s disease; they followed by endorectal pull-through (Soave tend toward total colonic aganglionosis. Both procedure). Hirschsprung’s disease and ganglioneuroblas- tomas manifest aberrations of neural crest cell Adult growth and development. Radiologists generally perform a barium Occasionally a mild form of what appears to be enema when suspecting Hirschsprung’s disease. Hirschsprung’s disease is detected in adults. A low-osmolality water-soluble contrast enema This acquired intestinal aganglionosis is often has also been used. Although a contrast enema labeled adult Hirschsprung’s disease, but this tends to be diagnostic in most, in neonates a term is tenuous at best. Biopsy often reveals transition zone is not well defined during the a ganglionitis and loss of neurons. In some first several weeks of life, and a normal exami- patients, with time, the involved segment nation does not exclude the diagnosis (Fig. 5.4). becomes more extensive. Whether such At times uncoordinated contractions are acquired intestinal aganglionosis is indeed a detected in the aganglionic segment. variant of Hirschsprung’s disease, an allergic In total colonic aganglionosis a contrast manifestation, or some other as yet undefined enema reveals a microcolon or a transition zone condition, is speculation. in the small bowel, or, rarely, it is even normal. Presentation in adults is generally similar A definitive diagnosis is made by rectal but milder to that seen in children. It is diag- biopsy. In some infants a full-thickness biopsy is nosed with a barium enema, anorectal manom- necessary. At times biopsy reveals ganglion cells etry, and tissue biopsy. Occasionally adult in the face of an abnormal barium enema, and Hirschsprung’s disease mimics rectal Crohn’s 195

COLON AND RECTUM disease; manometry helps distinguish between Short Colon Syndrome these two. In the congenital short colon syndrome the colon is either entirely or partially replaced by Allergic Colitis in Infancy a dilated pouch. In the partial type some normal-appearing colon is evident between the Allergic colitis, such as an allergy to cow milk and a dilated pouch; in the complete proteins, tends to mimic the barium enema variety the ileum inserts directly into a pouch. appearance of Hirschsprung’s disease.A barium Some of these infants have associated anorectal enema reveals an irregular rectal narrowing and malformations and colourinary fistulas. This a transition zone (34); rectal biopsies identify condition appears to be more common in ganglion cells and a inflam- northern India than in other regions. matory infiltrate. Symptoms resolve after diet change. Trauma Cystic Fibrosis Perforation Cystic fibrosis is discussed in more detail in Most colon perforations manifest as a pneu- Chapter 4. Mentioned here are findings perti- moperitoneum and are readily detected. A nent to the large bowel. Some authors use the retroperitoneal perforation, on the other hand, term fibrosing colonopathy or severe indetermi- is more difficult to detect; at times no perfora- nate colitis to describe colonic changes. tion is evident initially, but an abscess or A child with cystic fibrosis developed ascend- hematoma develop later. ing colon diverticulitis (35). Penetrating injuries to the colon are usually Patients with cystic fibrosis receiving large managed by a diverting colostomy, although the doses of pancreatic enzymes develop colonic trend is toward primary repair. strictures. Histologically, these strictures consist of chronic inflammation, extensive collagen Obstetrical Trauma deposition, fibrosis, and ulcerations. These strictures are probably different from Endorectal and transvaginal US are useful to those seen in Crohn’s disease. Confusing the evaluate sphincter injury after childbirth issue is that several of these patients have devel- trauma, although endorectal MRI appears supe- oped an inflammatory bowel disease. Whether rior in establishing the site and extent of a tear; this indeed represents classic inflammatory MRI also evaluates the integrity of individual bowel disease or is a sequela of cystic fibrosis anal sphincter muscles. and thus a separate entity is conjecture. Abnormal barium enema findings are common in children with severe cystic fibrosis Wall Thickening and suspected distal bowel obstruction unre- sponsive to medical management and consist An uncommon cause of colonic wall thickening, of strictures, loss of haustra, and longitudinal generally involving mostly right colon in other- foreshortening. Computed tomography shows wise asymptomatic cirrhotic patients, is conges- bowel wall thickening, mesenteric infiltration, tion secondary to . increased pericolonic fat, and mural striation, findings more prominent in the proximal colon. Patients with cystic fibrosis developing Inflammation/Infection Clostridium difficile colitis do not develop Detection of Colitis watery . Therapy for impaction and related conditions is unsatisfactory, and CT Focal or diffuse colonic wall thickening is the detection of a pancolitis in such a clinical primary CT finding of colitis. Although such setting should suggest antibiotic-associated (C. thickening is abnormal, it is nonspecific and difficile) colitis (36). occurs not only with various colitides but also 196

ADVANCED IMAGING OF THE ABDOMEN with some tumors and other infiltrative condi- Some of the infective, drug-related and tions. Similarly, the target sign (discussed in ischemic colitides mimic inflammatory bowel Chapter 4) is abnormal but nonspecific; it is, disease in their appearance; they are classified however, a marker for colitis and some infiltra- separately once a specific etiology is established. tive conditions but is not found with neoplasms. In particular, an etiology other than Crohn’s The term target sign is also used by ultrasono- disease or ulcerative colitis should be sought graphers when describing an intussusception. if a previous colitis resolves. Occasionally Differentiating patients by clinical presentation, described is a nongranulomatous ulcerative some investigators use the term colitis synony- manifesting with severe chronic mously with inflammatory bowel disease, diarrhea; even after an extensive investigation, although in a broader sense these are not the no specific diagnosis is made. same entities. Most patients with inflammatory bowel Using criteria of mucosal thickness >1.5mm, disease have a chronic, indolent presentation. bowel wall thickness >4mm, mucosal irregu- An occasional patient, however, is first seen with larity, absence of haustra, and terminal ileal an acute massive bleed or acute episode of thickness >4mm, hydrocolonic US in ulcerative severe colitis. Even toxic has mani- colitis and Crohn’s patients achieved 100% fested during an initial presentation. sensitivity in detecting active inflammatory A number of indices measure disease activity, bowel disease and 87% in identifying disease but most have had limited clinical adoption. An extension (37). interesting one involves use of the water-soluble Technetium-99m (Tc-99m)–hexamethyl- radiographic contrast agent iohexol. Urinary propyleneamine oxime (HMPAO) leukocyte excretion of ingested iohexol is significantly scintigraphy is a noninvasive test requiring no higher in patients with active inflammatory bowel preparation and is readily performed bowel disease than in those with quiescent even in ill patients. It is a sensitive test for disease or in controls (39). inflammation, being positive even in a setting Several studies have documented a lower of normal barium studies in patients later seroprevalence of Helicobacter pylori infection shown to have Crohn’s disease or ulcerative in patients with Crohn’s disease and ulcerative colitis. In patients with acute inflammatory and colitis than in controls. infectious colitis, Tc-99m-HMPAO leukocyte Inflammatory bowel disease is not limited to scintigraphy achieves sensitivities and the bowel, but also involves hepatobiliary, mus- specificities >80% in detecting involved seg- culoskeletal, ocular, dermatologic, and other ments. Tc-99m–2,3-dimercaptosuccinic acid organ systems. A possible association with (DMSA) scintigraphy reaches an overall sensi- glycogen storage disease type IB exists.An asso- tivity and specificity of >90% in detecting bowel ciation exists between inflammatory bowel inflammation (38). disease and sclerosing cholangitis and cholan- 18F-fluoro-deoxy-D-glucose (FDG) PET is giocarcinoma, although a relationship between primarily a neoplasm imaging agent, yet colonic and disease activity is not increased uptake is also evident in other hyper- straightforward; after liver transplantation metabolic states such as acute enterocolitis. for sclerosing cholangitis, inflammatory bowel disease can be reactivated despite maintenance immunosuppression. Likewise, colon carcinoma has developed after liver transplantation. Thus Inflammatory Bowel Disease serial colon cancer screening is necessary after General Findings liver transplantation.

The term inflammatory bowel disease is Pathologic Findings reserved by most authors for Crohn’s disease and ulcerative colitis. The term is also used by The presence of crypt abnormalities, basal some authors to describe a similar-appearing plasmacytosis with chronic inflammation, and colitis when a specific underlying disorder is distal metaplasia point toward in doubt, at times prefacing the term with inflammatory bowel disease rather than other nonspecific or indeterminate. colitides. Thr histology of a colorectal biopsy 197

COLON AND RECTUM suggests Crohn’s disease if epithelial granulo- sis. Nevertheless, it is difficult to place some mas, microgranulomas, or isolated giant cells patients in the proper perspective. For instance, are detected; these findings, however, are often a clinical, radiographic, endoscopic, and histo- lacking from biopsies of patients with obvious logic follow-up in a patient with right-sided Crohn’s disease. In some patients a diagnosis of colitis consisting of multiple shallow ulcers, indeterminate colitis is appropriate. erosion, and stenoses and sparing of the rectum Biopsy in ulcerative colitis reveals an irregu- and left colon appeared to exclude Crohn’s lar or villous surface, a decrease in mucous disease, tuberculosis, yersiniosis, Behçet’s content, and crypt atrophy. Initially diffuse disease, and ischemic colitis (41); the authors small ulcers develop surrounded by inflamma- concluded that the patient was indeed suffering tion and hyperemia. With disease progression from right-sided ulcerative colitis. the bowel wall thickens and lumen narrows. The is generally associated muscularis mucosa thickens markedly and fore- with ulcerative colitis, on rare occasions even shortens, leading to shortening of colonic being an initial manifestation of this disease. length. In distinction to Crohn’s disease, a vas- One should keep in mind, however, that toxic culitis is uncommon in ulcerative colitis. A megacolon is also encountered in severe acute transmural lymphocytic phlebitis, however, is Crohn’s disease and some infectious colitides. detected in some patients. Postinflammatory polyps, also called pseudopolyps, are a common finding in ulcera- Imaging tive colitis, although they also develop in a number of other colitides, including some infec- The role of double-contrast barium enema and tions.With partial healing the overlying mucosa colonoscopy in diagnosing both Crohn’s disease becomes hyperplastic. In some patients these and ulcerative colitis is well established. A polyps become sufficiently large and extensive number of studies have concluded that the to obstruct bowel lumen. These polyps can double-contrast barium enema and colono- cause a protein-losing . scopy are complementary imaging modalities for optimal detection of all mucosal and struc- tural colonic lesions, with the exception of those that do not distort the mucosa. Differential Diagnosis The terminal ileum is often involved in Clinical Crohn’s disease but is spared in ulcerative colitis (with the exception of backwash ). The Although in most patients differentiation barium enema appearances of terminal ileal between Crohn’s disease and ulcerative colitis is Crohn’s disease and backwash ileitis are quite straightforward, in a small subset radiologic different, and radiologists readily differentiate studies, colonoscopy, and biopsy do not differ- these entities. entiate with any degree of certainty between In Crohn’s disease CT identifies thickening of these two entities. An attempt at differentiation diseased bowel in most patients, and in the using serologic testing has had rather limited acute phase such thickening is universal. The success. Intestinal mucosal lymphocytes iso- bowel wall has a homogeneous appearance in lated mostly from lamina propria contain Crohn’s disease, but in ulcerative colitis it ranges higher levels of CD19, transferrin receptor, T- from homogeneous to a target sign (discussed cell receptors alpha/beta, and T-cell receptors in Chapter 4). The outer colonic contour tends gamma/delta in ulcerative colitis patients than to be smooth in severe ulcerative colitis; in in Crohn’s patients (40); the clinical significance Crohn’s disease it can be either smooth or of these findings is not clear. irregular. In a vast majority of patients ulcerative colitis Rectal involvement results in presacral space extends from the rectum proximally for varying widening and is found both with Crohn’s proc- lengths, with a pancolitis found in a minority. titis and ulcerative colitis. Computed tomogra- Skip areas are not found, and in a setting of a phy shows this widening to be mostly secondary right-sided colitis with rectal sparing ulcerative to infiltration by fat-containing linear and colitis should not be in the differential diagno- nodular soft tissue densities. 198

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In young adults with chronic abdominal pain Crohn’s disease is most often found in the distal and bowel dysfunction, some authors establish small bowel, disease confined to the colon an arbitrary upper normal US bowel wall thick- and rectum is not uncommon. A later age of ness, with inflammatory bowel disease sug- disease onset appears related to an increased gested if this thickness is exceeded. Thus in prevalence of colorectal rather than small bowel consecutive outpatients, use of a 7-mm upper involvement. normal bowel wall thickness achieved a sensi- In a retrospective cohort study of patients tivity of 74% and specificity of 98% in suggest- with colorectal Crohn’s disease, distribution was ing inflammatory bowel disease (42); these segmental in 40%, total in 31%, and left-sided in findings could be further subdivided into an 26% (45); perianal or rectal fistulas developed in 84% sensitivity and 98% specificity for Crohn’s 37%. In those patients attaining clinical remis- disease and 38% and 98%, respectively, for sion, the 5-year cumulative relapse rate was ulcerative colitis. 67%. Half of these patients underwent a resec- After distending the large bowel with water tion within the first 10 years, and half of these (hydrocolonic US), US normally differentiates ultimately required an ileostomy.Analysis of the five wall layers having different echogenicities. cause of death of patients with Crohn’s disease The colonic wall is hypoechoic and thickened, during 1973 to 1980 in Rochester, New York, and these five colonic wall layers cannot be visu- found that Crohn’s disease was the causative alized in most Crohn’s disease patients, but they factor in 44% of deaths, but during 1981 to 1989 tend to be preserved in ulcerative colitis; loss of deaths due to Crohn’s disease decreased to 6% this layer stratification is due to fibrosis and (46). implies an irreversible change. Postcontrast MR in colonic Crohn’s disease reveals transmural bowel wall enhancement, a Imaging finding distinct from typical ulcerative colitis Early colonic manifestations of Crohn’s disease where enhancement is limited to the mucosa consist of lymph follicle prominence and pres- and MRI identifies less bowel wall thickening. ence of aphthae. These are readily detected with Thus after lumen distention with oral and rectal a double-contrast barium enema but are not fluid, pre– and post–gadolinium (Gd)–diethyl- visualized with CT. The presence of aphthae enetriamine pentaacetic acid (DTPA) HASTE implies active colitis but is not pathognomonic and dynamic fast low-angle shot (FLASH) axial of Crohn’s disease (Fig. 5.5); lymphoid hyper- and coronal images allowed differentiation of Crohn’s disease and ulcerative colitis in 81% of 27 patients with inflammatory bowel disease (43).Low-field MRI (0.1T) tends to overestimate and underestimate disease extension both in Crohn’s patients and in ulcerative colitis patients. Although Tc-99m-HMPAO–white blood cell scintigraphy is very sensitive and specific in detecting colonic inflammation (44), it has a limited role in differentiating active colonic Crohn’s disease from ulcerative colitis. Discon- tinuous uptake suggests Crohn’s disease, but some children with ulcerative colitis also have discontinuous uptake.

Crohn’s Disease Clinical Crohn’s disease is discussed in more detail in Chapter 4. Covered here are those aspects Figure 5.5. Cecal Behçet’s disease. Aphthae are scattered related to the colon (Crohn’s colitis). Although throughout. Crohn’s disease has a similar appearance. 199

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detecting and evaluating the extent of Crohn’s disease. Some authors suggest that specific imaging findings can suggest whether a particular stage of Crohn’s disease is reversible or not. Thus presence of a target sign suggests that fibrosis has not yet developed and the underlying abnormalities are reversible with appropriate therapy.Whether this is indeed so remains to be proven.

Complications The earlier literature rarely mentioned cancer developing in a setting of Crohn’s disease. Some of these publications should be held suspect because a number of these patients were misdi- agnosed. More recent publications document an Figure 5.6. Crohn’s disease. Extensive filiform polyposis is increased incidence of cancer in bowel involved present. (Courtesy of Arunas Gasparaitis, M.D., University of by Crohn’s disease. Typically the interval from Chicago.) initial Crohn’s diagnosis until cancer is detected is up to 20 years. Some cancers are multiple. plasia, on the other hand, exists without disease They have developed in a defunctionalized activity. rectal stump. An occasional one involves a Progression of inflammation leads to filiform Crohn’s-induced anorectal sinus tract or fistula. polyposis and diffuse intramural thickening Patients with inflammatory bowel disease (Fig. 5.6). With established disease, the presence (both Crohn’s disease and ulcerative colitis) of homogeneously thickened bowel wall during tend to develop a diffusely infiltrating and an arterial phase CT study generally implies the metastasizing carcinoma, called linitis plastica presence of fibrosis. of the colon. Most of these are adenocarcino- Magnetic resonance imaging is very accurate mas. Radiologically, these cancers tend to mimic in detecting active Crohn’s colitis (Fig.5.7).After a benign stricture, and at times even a biopsy is oral bowel opacification with a 2.5% mannitol nondiagnostic. solution, axial and coronal breath-hold MRI Anal fissures and low anal fistulas are using contrast-enhanced T-1 weighted FLASH common in Crohn’s disease and tend to be asso- and T2-weighted HASTE sequences identified ciated with an adjacent phlegmon or abscess. more diseased segments than comparable Most sinus tracts and fistulas in a setting of barium studies (47). Current evidence suggests Crohn’s colitis end blindly or are enteroenteric; that a hydro-MRI study is very reliable in both an occasional fistula extends to an unusual

A B Figure 5.7. Comparison of MR HASTE sequences (A) and contrast-enhanced GRE sequences (B) of bowel segment involved with Crohn’s disease. (Courtesy of Wolfgang Luboldt, M.D., Johann Wolfgang Goethe University, Frankfurt-am-Main.) 200

ADVANCED IMAGING OF THE ABDOMEN location. A high or complex anal fistula or a with known ulcerative colitis, the number of rectovaginal fistula is uncommon, with only a relapses/year after pregnancy is lower com- minority of these patients having obvious pared to a similar period before pregnancy. Crohn’s (the imaging approach to Ulcerative colitis usually manifests after fistulas is discussed later in this chapter; see puberty, with only a minority detected earlier. Fistula). Most patients have a chronic, relapsing course. Most urinary tract fistulas involve the A common clinical finding is bloody diarrhea, bladder, with only a rare one extending into the and its absence should suggest another diagno- ureter, urethra, or Bartholin’s gland. A rare sis. Experienced clinicians can probably recall colonic fistula crosses the diaphragm; even an occasional patient first presenting with ful- developing a colobronchial fistula. minant toxic colitis. Superimposed infections are common and Past teaching held that once ulcerative often account for acute flare-ups. colitis was established, it changed little in Similar to the small bowel, only a rare extent, a finding no longer believed to be true. colocolic intussusception has been reported in Over a several year period idiopathic ulcerative Crohn’s colitis. in most patients remains similar in extent, in a minority spreads proximally and, Ulcerative Colitis less often, decreases in extent. Clinical Associated Conditions In large parts of Europe the incidence of ulcer- ative colitis in school-age children has been An association between ulcerative colitis and about 1.5 to 2.0 per 100,000 children per year for primary sclerosing cholangitis or pericholangi- the last several decades (48). In some parts of tis is well known. Less well known is an occa- the world the reverse is true, namely, the inci- sional association between and dence of ulcerative colitis is decreasing while both ulcerative colitis and Crohn’s disease. Crohn’s disease is increasing. Prevalence is Occasionally pancreatitis manifests before onset greater in some families and ethnic groups, and of ulcerative colitis. Complicating the picture is an inheritance pattern is evident in some. an association of and aza- The etiology and pathogenesis of ulcerative thioprine therapy. colitis are unknown. An abnormal immune An occasional association exists between system response appears to be involved, ulcerative colitis and pyoderma gangrenosum, although whether the immune system itself is glomerulonephritis, systemic lupus erythe- abnormal or whether it is responding to some matosus, sarcoidosis, and Ménétrier’s disease. other abnormality is conjecture. Significantly Whether similar genetic or immunologic path- increased secretion of mast cell tryptase, a ways are involved is speculation. highly mast cell specific protease, suggests mast One patient developed ankylosing spondyli- cell involvement (49). These patients have a tis at age 28 years, ulcerative colitis at age 49 higher prevalence of allergic symptoms, and years, and chronic granulocytic leukemia at age skin tests show increased rates of immediate 59 years (51). An uncommon association and delayed hypersensitivity than controls. The appears to exist between ulcerative colitis and concordance rate of ulcerative colitis is higher rheumatoid arthritis. in monozygotic twins than in dizygotic twins, although not to the extent seen in Crohn’s Imaging disease. Thus in a Danish study of nearly 30,000 twins the proband concordance rate among The traditional imaging study to diagnose and monozygotic twins was 58% for Crohn’s disease quantitate the extent of involvement was a and 18% for ulcerative colitis and among dizy- double-contrast barium enema. In parts of gotic twins the rates were 0% and 4%, respec- Europe a single-contrast enema, using air as a tively (50). contrast agent, is performed. Gastroenterolo- One interesting sidelight is that a previous gists prefer colonoscopy and biopsy. appendectomy appears to protect somewhat Presacral space widening due to fatty infiltra- against future ulcerative colitis. Also, in women tion is common once the disease is established 201

COLON AND RECTUM and is readily apparent with most imaging dicts and localizes acute inflammation, but modalities. Loss of rectal valves of Houston is a negative study does not exclude acute in- also common. flammation. Also, sites of positive leukocyte Early in the course of disease a CT study is scintigraphy become negative after leukocyte normal and thus for early disease detection CT apheresis or glucocorticoid therapy, and thus is not warranted. With more extensive bowel leukocyte scintigraphy appears useful in evalu- involvement CT identifies a colonic wall target ating treatment response.Also, Tc-99m-HMPAO sign. The hypertrophied mucosa is seen as a soft scintigraphy appears to predict proximal tissue density surrounded by a lower density disease extension better than CT. ring representing fatty submucosal infiltration, this in turn is surrounded by a soft tissue Complications density muscularis propria. As already men- tioned, such a target sign is not specific for Perforation in a setting of toxic megacolon is ulcerative colitis, but is also found in a number a well-recognized complication of ulcerative of other colitides. Bowel wall thickening and colitis. Instead of frank perforation, an occa- lumen narrowing evolve with chronicity. sional patient with severe ulcerative colitis Ultrasonography assesses both the extent and develops retroperitoneal emphysema. activity of ulcerative colitis and follows the Dysplasia is believed to be a precursor in the response to medical treatment. Using a thick- pathway to cancer in ulcerative colitis. Detecting ened bowel wall and loss of haustra as evidence dysplasia is generally in the province of a of disease in patients with active ulcerative pathologist, although at times the colonoscopic colitis, US correctly identified diseased seg- or barium enema appearance suggests this con- ments in 74% of patients (52); also, US re- dition by finding nodular protrusions, irregular vealed bowel wall thickening decreasing after mucosa, and minute spiculations. If detected medical therapy in patients showing clinical incidentally, such a finding warrants a biopsy, improvement. yet for cancer surveillance and dysplasia detec- Doppler US reveals increased portal and tion most physicians rely on histopathology mesenteric blood flow and a lower resistance for these notoriously difficult-to-detect tumors. index in the superior mesenteric artery in those Cancers developing in a setting of ulcerative with active disease but not in those with quies- colitis typically are flat or plaque-like rather cent disease.Active Crohn’s disease or ulcerative than polypoid or ulcerated as seen in nondis- colitis involving the left colon lead to a marked eased bowel. Surrounding diseased mucosa increase in inferior mesenteric artery blood makes early cancer detection even more flow (53); compared with controls, Doppler US difficult.An underlying cancer in a colonic stric- reveals increased velocity, flow volume, and a ture is readily missed both radiologically and decreased pulsatility index. These findings colonoscopically. In some, previous endos- should be balanced against laser Doppler copy did not reveal either dysplasia or cancer, flowmetry of rectal blood flow; flowmetry with an advanced adenocarcinoma being later detected significantly reduced rectal perfusion discovered. in those with ulcerative colitis but not Crohn’s Prevalence of colon cancer increases in a colitis (54); suggesting that impaired local blood setting of pancolitis. Also, the risk of colorectal flow plays a pathogenetic role in ulcerative dysplasia and carcinoma appears increased by colitis. the presence of primary sclerosing cholangitis. Postcontrast MR reveals marked mucosal Surveillance colonoscopic biopsies are useful enhancement of diseased segments and relative to detect dysplasia, with high-grade dysplasia submucosal and muscle sparing. Because of this being considered a precursor to cancer. Never- limited transmural involvement, MRI tends theless, in spite of the extensive literature on to underestimate the extent of disease. A fat- surveillance colonoscopic biopsies, no consen- suppression technique is helpful in outlining sus exists on its clinical value in patients with diseased segments. ulcerative colitis. In general, surgery should be Technetium-99m-HMPAO leukocyte scintig- considered in patients with an underlying stric- raphy is useful in evaluating the extent and sites ture even if a biopsy is negative for dysplasia or of disease activity. This noninvasive study pre- malignancy. 202

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A number of reports describe primary Crohn’s disease. Some of the extraintestinal colonic lymphoma developing in a setting of complications of ulcerative colitis have a clini- ulcerative colitis. Complicating the picture are cal course independent of bowel disease and reports of colonic lymphoma misdiagnosed as are not affected by a colectomy. Currently ulcerative colitis; superficial colonic biopsies in total proctocolectomy is rarely performed on these patients are believed to be compatible an elective basis for ulcerative colitis because with ulcerative colitis, with lymphoma mani- of associated complications, including sexual festing only several months later. In distinction dysfunction. to ulcerative colitis, colonic mucosal abnormal- Among patients with Crohn’s disease who ities resolve after therapy for lymphoma. underwent total colectomy, end ileostomy, Thromboembolic disease is a known compli- and an oversewn rectal stump, over half later cation of ulcerative colitis. Massive pulmonary required a proctectomy (56); of note is that 23% emboli and even dural sinus thrombosis have of these patients later developed small bowel occurred. recurrence requiring surgery. Pulmonary interstitial fibrosis and fibrosing Some patients with ileostomies performed alveolitis have developed in a setting of ulcera- for ulcerative colitis develop polyps at their tive colitis. ileostomy stomas; most of these are inflamma- Infections develop readily, and some acute tory polyps, but an occasional neoplastic polyp flare-ups are secondary to superimposed infec- also develops. tion. Infection should be suspected in a patient being treated with steroids who becomes fulmi- nant. In some countries, ulcerative colitis Ileorectal Anastomosis patients receiving steroids have developed pul- A subtotal colectomy leaves behind a diseased monary or intestinal tuberculosis. Severe infec- rectum with its associated complications, in- tion can result in pseudomembranous colitis cluding the risk of cancer. developing even without antibiotic use. An interesting retrospective study found that Surgery for Colonic Inflammatory 21% of patients undergoing a subtotal or total colectomy for ulcerative colitis required reoper- Bowel Disease ation for postoperative acute ; none Surgical approaches to colonic involvement by of the patients undergoing colectomies for other inflammatory bowel disease consist of (1) total reasons (mostly cancer) developed acute proctocolectomy with an ileostomy, (2) total cholecystitis (57). colectomy with an ileorectal anastomosis, and (3) colectomy with a mucosal proctectomy and ileoanal anastomosis (ileal pouch). Ileal Pouch The choice of surgery is influenced by the An ileoanal anastomosis and creation of an type of inflammatory bowel disease. A retro- ideal pouch eliminates all diseased rectal spective study of 86 patients with colonic mucosa and is the current therapy for both Crohn’s disease who underwent a single-stage familial polyposis syndrome and ulcerative proctocolectomy and 65 who underwent total colitis. An ileoanal anastomosis is performed in colectomy and ileorectal anastomosis found two stages: resection, anastomosis, and a divert- that 29% of proctocolectomy patients and 68% ing loop ileostomy initially, followed by closure of ileorectal anastomosis patients developed of loop ileostomy several months later. symptomatic recurrence (55); after proctocolec- A special ileoanal barium study has been pro- tomy the 5-, 10-, and 15-year cumulative re- posed to predict the frequency of bowel move- operation rates for recurrence were 13%, 16%, ments and measure pouch spasticity (58); with and 26%, compared to 29%, 46%, and 48%, the patient standing, barium sulfate is instilled respectively, after ileorectal anastomosis. into the pouch until reflux into more proximal Ileostomy small bowel occurs. The total volume infused and volume voided are measured. The clinical A total proctocolectomy is curative for bowel usefulness of such a quantitative test remains to manifestations of ulcerative colitis but not be determined. 203

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A leak, adjacent inflammation, abscesses, and discussed later in this chapter; see Vascular fistula formation are immediate complications Lesions (Bleeding). related to creation of an ileoanal pouch. A con- Acute right colonic diverticulitis is an trast enema is commonly performed to check uncommon diagnosis in the Western world, for stricture, leak, or other complication prior to although the actual prevalence is not known ileostomy closure. Strictures developing on a because some of these patients are treated con- more chronic basis are evaluated by endoscopy, servatively. A higher prevalence of right colonic pouchography, CT, and endoluminal US. diverticulitis is found in the Orient.Among con- Coronal CT visualizes most anastomoses and secutive patients admitted to Singapore General adjacent structures. A high accuracy is claimed Hospital with diverticular disease, 42% had for endoluminal transpouch US, but this study right-sided diverticula, 34% had left-sided, and has not achieved popularity. 24% had bilateral (61); of these patients, 47% Postoperatively, functioning ileal pouch had rectal bleeding, 36% diverticulitis, 12% mucosa undergoes colonic metaplasia. Pouch obstruction, and the rest presented with fistulas. inflammation () is a late complication In the West, a correct preoperative diagnosis of and develops in about 10% to 30% of patients. right colic diverticulitis is usually not made. A Although the underlying cause of pouchitis is not uncommon scenario is a preoperative diag- not clear,in some patients pouchitis presumably nosis of acute appendicitis in an adult, found to represents recurrent ulcerative colitis. Patients represent right colonic diverticulitis at surgery. with primary sclerosing cholangitis develop A necrotic cecal carcinoma is also in the clinical significantly more severe chronic pouch differential diagnosis. inflammation than those without cholangitis Left-sided diverticulitis in younger adults (59). Liver transplantation does not alter the tends to be more virulent than in the elderly. course of pouchitis in most patients. Pouchitis These patients have a higher rate of emergency appears to be related to ulcerative colitis surgery, and an erroneous preoperative diag- because it is uncommon in a pouch created for nosis, such as appendicitis, is more often familial polyposis. entertained. Pouchitis is detected both by a barium study and endoscopy. The final diagnosis is based on Imaging histologic findings. A long-term complication of an ileal pouch is Quite often a patient with typical clinical fistula formation. The pouch and any related findings of acute sigmoid diverticulitis does not fistulas are readily evaluated with a barium undergo any imaging but is treated medically. enema, although MRI is also useful in evaluat- Only in patients with an atypical presentation or ing pelvic fistulas (60). For poorly understood those not responding to medical management is reasons, cholelithiasis is relatively common in CT obtained to evaluate for possible complica- patients after an ileoanal anastomosis; most tions.Although CT readily detects diverticulitis, stones are composed primarily of cholesterol. the diagnosis is generally already suspected One late complication after an ileoanal anas- clinically and a surgeon is more interested in tomosis is small bowel volvulus, believed to be presence of complications. In some European related to surgical manipulation and the result- centers, on the other hand, a water-soluble con- ant mesenteric tension. trast enema and, more recently, CT are obtained during the acute attack. Ultrasonography has been proposed in a setting of acute diverticulitis; it is of particular Diverticulitis value in women for whom a gynecologic abnor- Clinical mality is in the differential diagnosis.A contrast enema should be approached with caution in Symptomatic diverticular disease tends to man- these generally acutely ill patients; first, a ifest in one of two ways: either as an infection barium enema is contraindicated because of a evolving into diverticulitis or as a lower gas- possible perforation into the peritoneal cavity trointestinal hemorrhage, often massive but (keeping in mind that a free perforation is a typically self-limiting. The latter condition is known complication of acute diverticulitis), and 204

ADVANCED IMAGING OF THE ABDOMEN if a contrast enema is needed a water-soluble Table 5.2. Computed tomography findings in acute sigmoid contrast agent is employed; second, these sick diverticulitis patients tolerate an enema poorly, spasm is Focal sigmoid wall thickening common, and, due to the inherent low radi- Arrowhead sign (see text) ographic contrast of water-soluble contrast Inflammation agents, details are difficult to evaluate. Also, Pericolic although water-soluble contrast agents are Sigmoid mesentery innocuous in the peritoneal cavity, with a per- Phlegmon foration invariably infected colonic matter is Abscess Intramural also spilled. Pericolic Imaging studies are also requested if a patient Fistula does not improve with medical therapy and Obstruction surgery is contemplated. For this latter indica- Sigmoid obstruction tion imaging is performed primarily to exclude Small bowel obstruction complications of diverticulitis, namely Portal and mesenteric vein gas abscesses, fistulas, or other abnormalities such Peritonitis as a necrotic tumor. Further imaging is generally requested once an acute attack has subsided and if an elective Although diverticula are often identified, the resection is contemplated. At this point an presence of diverticula is not a sign of divertic- abscess is generally not a consideration, as the ulitis. Focal mural thickening is often found in surgeon is interested in the presence of any a setting of chronic diverticular disease without other disease, namely, a necrotic, infected evidence of acute inflammation. Some radiolo- cancer. Clinically, such a cancer can mimic gists subdivide CT findings of diverticulitis into diverticulitis. The controversy here revolves mild and severe, with the latter including a around the best modality with which to detect mesenteric abscess, fistula, and peritonitis, but a necrotic colon cancer. In this setting I prefer such differentiation is generally obvious a double-contrast barium enema over CT, clinically. although gastroenterologists argue for colono- An arrowhead sign, consisting of an arrow- scopy. A differentiation between a necrotic head-shaped collection of contrast located cancer and diverticulitis is usually straightfor- within a thickened colon wall, was identified by ward with a barium enema but can be rather postcontrast enema CT imaging in 27% of subtle with CT. To illustrate this dilemma, a ret- patients with a final clinical diagnosis of colon rospective study of patients with proved diver- diverticulitis (63); an inflamed diverticulum, ticulitis and colon cancer, with readers blinded consisting of a rounded, paracolic outpouching to diagnosis, found that pericolic inflammation with surrounding fat stranding, was found in and colonic involvement >10cm in length were 33% of these patients. Neither the arrowhead the most significant findings for diverticulitis, sign nor an inflamed diverticulum was found in whereas enlarged pericolic lymph nodes and any other condition in the authors’ study of 150 intraluminal tumor were the most significant consecutive patients suspected of diverticulitis, findings for colon cancer (62); using these crite- and thus both achieved 100% specificity; of ria, a prospective CT study achieved a correct interest is that almost half of the inflamed diver- unequivocal diagnosis in only 40% of patients ticula identified contained high attenuation with diverticulitis and 66% of patients with material. colon cancer (62), not a very satisfactory result. The results of US in detecting and evaluating Also, some patients with diverticulitis have sigmoid diverticulitis are mixed. Comparison enlarged lymph nodes, thus further confusing studies of CT and US in patients suspected of the differential between diverticulitis and a having acute colonic diverticulitis reveal necrotic cancer. similar sensitivities and specificities for CT and Table 5.2 outlines typical CT findings in acute US; more pericolic diverticular abscesses are sigmoid diverticulitis. Not all findings are, identified with CT than US. Either a concomi- of course identified in any one patient. Most tant adynamic ileus or an obstruction tends to commonly detected is pericolic inflammation. limit adequate US visualization of the region in 205

COLON AND RECTUM question. Some gas-containing abscesses mimic ponent enhances postcontrast. As with CT, a bowel loops. Ultrasonography identifies some necrotic colon cancer is difficult to distinguish noninflamed diverticula, with these diverticula from diverticulitis with MR. often containing echogenic material. Ultra- In differentiating right-sided colonic diverti- sonography findings of diverticulitis include culitis from a carcinoma, detection of an bowel wall thickening, seen as a thick hypoe- inflamed diverticulum by CT had a mean sensi- choic layer, and pericolonic fat inflammation, tivity of 87% and specificity of 93%, while pre- seen as a hyperechoic layer. The suspect diver- served wall contrast enhancement had a mean ticulum, if identified, appears as a hyperechoic sensitivity and specificity of 90% and 95%, focus adjacent but outside the colonic lumen. A respectively (64). Follow-up US in patients flask-like or arrowhead-like hypoechoic appear- believed to suffer from acute right colonic diver- ance is occasionally detected in colon segments ticulitis reveals spontaneous evacuation of the affected by diverticulitis. Fistulas have a linear, inflamed diverticular content into the colonic hypoechoic appearance. lumen. Overlying intestinal gas is avoided with endorectal US. Occasionally a perforation, Complications abscess, or fistula not shown on transabdominal US is identified with endorectal US. Complications of diverticulitis include fistula, Bowel wall thickening, abscesses, fistulas, and abscess, perforation with peritonitis, and sinus tracts are well detected with MRI (Fig. obstruction. The latter complication involves 5.8). Surrounding inflammation appears on either colon or an adjacent loop of small bowel. T1-weighted images as hypointense stranding Among patients with diverticular fistulas, within hyperintense fat. The inflammatory com- slightly less than half are colovesical, similar

B

A

Figure 5.8. CT (A) and MR (B,C) colonography of diverticulitis. Axial CT is commonly used with suspected diverticulitis but value of MR is not yet established. (Courtesy of Wolfgang Luboldt, M.D., Johann Wolfgang Goethe University, Frankfurt- am-Main.) C 206

ADVANCED IMAGING OF THE ABDOMEN number are colovaginal and a few percent are Hartmann’s pouch or mucus fistula created, colocutaneous and coloenteric.Rare colouterine followed later by a second laparotomy to re- and colosalpingeal fistulas have been reported. establish colon continuity. One option feasible A rare fistula extends into the thigh and pres- in some patients is initial percutaneous abscess ents either as a septic arthritis or as subcuta- drainage, followed in a week or so by resection neous emphysema. A rare complication of and primary anastomosis, thus sparing the sigmoid diverticulitis is vertebral osteomyelitis. patient a temporary colostomy and a second Most fistulas are readily detected by CT. In fact, laparotomy. CT is superior to cystoscopy in detecting Surprisingly, some surgically treated patients colovesical fistulas. continue being symptomatic. Inferior mesenteric vein thrombophlebitis is an underappreciated complication of sigmoid Infective Colitis diverticulitis; CT reveals an enlarged and inflamed inferior mesenteric vein. At times gas Mentioned here are only those infections is identified within the vein lumen. Sigmoid primarily affecting the large bowel; others are diverticulitis is a common cause of multiple covered in Chapter 4. Patients with salmonella, liver abscesses and portal venous gas. shigella,or yersinia infection develop bowel wall On an acute basis, bowel obstruction is due thickening, a nonspecific finding.Yersinia infec- to inflammation and edema. Small bowel tion also leads to adenopathy and focal ulcera- obstruction develops if a loop of small bowel tions of involved bowel (Fig. 5.9). becomes adherent at the site of inflammation In patients with acute infectious diarrhea and or abscess. A persisting obstruction implies a a single identified enteropathogen, a majority fibrotic stricture and is an indication for resec- are due to invasive pathogens; the presence of tion. A barium enema can generally differenti- is almost pathognomonic for ate between a benign diverticular stricture and an invasive agent but this finding has a low one due to cancer. A correct barium enema dif- sensitivity. ferentiation between benign and malignant strictures was made in most patients with a documented sigmoid strictures (65); only one benign stricture was called malignant, but caution was advised for benign-appearing stric- tures; nine malignant strictures were called benign.

Therapy In general, a first episode of uncomplicated diverticulitis is managed conservatively. Most patients with a typical acute episode treated medically with bowel rest and antibiotics do not undergo surgery. Surgery is considered in those with recurrent attacks or those unresponsive to conservative therapy. Chronic diverticulitis has been treated laparoscopically. Similar to other laparoscopic procedures, patients have a faster recovery and shorter hospital stay than those undergoing conventional surgery. The procedure costs more than an open resection in the United States because of longer operating room time, but the reverse applies in Germany. Perforated sigmoid diverticulitis is generally Figure 5.9. Yersinia enterocolitis.A barium enema reveals ulcers resected, a colostomy performed, and a scattered throughout the rectum. 207

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Escherichia coli colonic involvement in 58% (69). Most often acute colonic involvement consists of discrete Enterohemorrhagic colitis is caused by a ulcers in the right colon. Coloenteric or recto- noninvasive E. coli serotype, often manifesting vaginal fistulas are not common with intestinal in outbreaks due to undercooked food. The con- amebiasis. tiguous right colon tends to be predominantly Tuberculous colitis and chronic amebic involved, with imaging findings mimicking colitis tend to have a similar imaging appear- either mild-to-moderate ischemic colitis or ance, although tuberculosis is more prone to Crohn’s disease. Computed tomography appears involve mesentery and small bowel (Fig. 5.10). to be more sensitive than conventional radi- ographs in identifying diseased segments (66). Hemolytic uremic syndrome associated with Schistosomiasis E. coli infection has an intestinal prodromal Schistosoma mansoni, or intestinal bilharziasis, phase, with a hemorrhagic acute colitis found is endemic in West Central Africa, the Arabian in some patients. In fact, in North America, peninsula, some Caribbean islands, and the hemolytic-uremic syndrome after E. coli hem- Atlantic Ocean side of South America. Chronic orrhagic colitis is the main cause of pediatric infection tends to localize mostly in mesenteric renal failure requiring kidney transplant. veins draining the colon; eggs are deposited During this prodrome phase color Doppler US in submucosal veins and pass into the bowel reveals a thickened, markedly avascular colonic lumen. Associated portal hypertension, hepa- wall. tomegaly, and splenomegaly develop eventually. Gastrointestinal bleeding in infected individuals Phlegmonous Colitis is from two sources: either direct colonic infes- Phlegmonous colitis is an often unrecognized tation or bleeding secondary and usually fatal condition caused by bacterial to portal hypertension. infection. In an autopsy study of patients with Schistosoma japonicum has been eradicated phlegmonous colitis, all had either underlying in Japan, and currently is found in China, hepatic or subacute liver atrophy Thailand, Philippines and Indonesia; Schisto- believed to be due to viral (67); phleg- monous colitis was not suspected prior to death. Pathologic findings consisted of cecal involvement (77%), edema and submucosal phlegmonous changes (100%), bacterial infec- tion (100%), no detectable mucosal injury (92%), and acute peritonitis (15%). At times total colectomy is necessary for adequate disease control.

Amebic Colitis Amebiasis, or infection by Entamoeba histo- lytica, ranges from asymptomatic carriers to a fulminant and necrotizing colitis. At times during an acute phase the clinical presentation suggests inflammatory bowel disease, with severe intestinal bleeding, progression to ful- minant colitis, or even perforation. Colonic mucosal necrosis is common. Among patients with fulminant amebic colitis seen at a referral center in Mexico, about half also had a coexistent amebic Figure 5.10. Descending colon stricture secondary to amebic (68). The reverse is also true; in 45 patients with colitis (arrow). A tuberculous stricture or one due to inflamma- amebic liver abscesses, colonoscopy revealed tory bowel disease can have a similar appearance. 208

ADVANCED IMAGING OF THE ABDOMEN soma mekongi is mostly in the Mekong valley; thickened valve lips, is a characteristic finding these have a similar bowel presentation and are but not always present. The terminal ileum a major cause of liver fibrosis and resultant is deformed, narrowed and suggests Crohn’s portal hypertension. Schistosoma intercalatum, disease. Colonic involvement tends to be seg- endemic in central Africa, affects the rectosig- mental, at times involving multiple sites. A moid and manifests with pain, diarrhea, and tuberculous stricture often mimics a benign- rectal bleeding. appearing colonic stricture such as is seen in Colonic ulcers, neovascularity, fibrosis, and Crohn’s disease (Fig. 5.11). Rarely, colonic tuber- giant cell granulomas surround S. mansoni eggs. culosis manifests as a diffuse pancolitis. Hyperemia and telangiectasia are the endo- Colonic tuberculosis does lead to fistulas, scopic findings of colonic infestation, indicative including an occasional duodenocolic fistula, of increased vascularity, changes also secondary but fistulas and sinus tracts are less common to portal hypertension developing in some than with Crohn’s disease. patients with schistosomal liver involvement. Tuberculous rectal involvement is uncom- Such portal colopathy is not pathognomonic for mon. A barium enema in these patients reveals this condition but is also found in patients with a stricture of variable length, deep ulcerations, portal hypertension due to other causes.A gran- and a widened presacral space; biopsy simply uloma can mimic an adenomatous polyp during yields a granulomatous infiltrate.Anal and peri- colonoscopy. anal tuberculosis results in findings similar to Computed tomography reveals a thickened, Crohn’s disease. poorly marginated bowel wall having varying Over the years a number of reports described contrast enhancement. These findings presum- cecal tuberculosis coexisting with a cecal ade- ably reflect underlying inflammation and portal nocarcinoma. Due to the distortion, even at hypertension. surgery an underlying carcinoma can be difficult to identify. Tuberculosis These patients respond to antitubercular therapy and often do not require surgery. Abdominal tuberculosis is discussed in more detail in Chapter 14. In endemic areas, about 10% of gastrointesti- nal tuberculosis involves the colorectum and consists of strictures, colitis and, least common, polyps (70). Symptoms tend to be those of chronic infection.A majority of intestinal tuber- culosis is secondary to pulmonary involvement. Biopsies often fail to establish a diagnosis, at times revealing granulomas, although non- specific inflammation is a more common histo- logic finding. Resected specimens reveal inflammation, caseating granulomas, and Lang- hans giant cells, all consistent with tuberculosis, but acid-fast bacilli are rarely isolated. A not atypical clinical history consists of con- stipation, weight loss, and abdominal pain, with occasional rectal bleeding. Blood tests and chest radiographs are often noncontributory. Massive rectal bleeding is uncommon. In its chronic form tuberculosis results in colonic strictures, deformity, ulcerations, polyps, and fibrous bands, with the right colon and ileum being most often Figure 5.11. Tuberculous colitis presenting as a stricture involved. The cecal lumen narrows. A wide, (arrow). An ameboma, ischemic stricture, or even inflammatory gaping ileocecal valve, often with deformed and bowel disease can have a similar appearance. 209

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A double-contrast barium enema reveals skip mycosis. At times aspiration from an infected lesions and multiple, transverse, or circumfer- mass provides the diagnosis. ential ulcers, with the ulcers ranging from Even with extensive involvement, once a diag- shallow to deep and having an uneven, nodular nosis of actinomycosis is established medical margin. Inflammatory polyps are common, therapy rather than resection is generally war- occasionally mimicked a malignancy. ranted. In practice, however, the diagnosis is difficult, and some patients are noncompliant with long-term antibiotic therapy. Actinomycosis Anisakiasis Actinomyces israelii, an anaerobic bacterium, is normally found in the upper gastrointestinal Anisakiasis is considerably more common in tract and here it rarely causes disease. In the the upper than in the pelvis, on the other hand, actinomycosis results colon. Several patients with ascending colon in fistulas, inflammatory tumors, strictures, and involvement by Anisakis simplex larvae pre- abscesses. It causes more harm in women and is sented with an acute abdomen. Imaging often associated with intrauterine devices. The identifies focal colonic wall thickening, mimick- diagnosis is often established by culture of a ing diverticulitis or ischemia. removed contraceptive device. With colonic involvement, generally rectosig- Viral moid, the induced marked fibrosis tends to mimic a colon cancer by barium enema, CT,and Herpes simplex colitis leads to aphthae and ero- endoscopy, except that a common hallmark of sions. Quite often only a short colonic segment actinomycosis is extensive fistulization, at times is involved. even cutaneously, an uncommon finding with a is rare in immuno- cancer. Thus a barium enema often reveals competent patients. Infection has led to ful- extensive fistulas, generally more than is seen minant hemorrhagic colitis. Imaging reveals with diverticulitis or even Crohn’s disease.Com- colonic wall thickening and ulceration, in some puted tomography shows a contrast-enhancing patients mimicking a neutropenic colitis (Fig. tumor, often containing a cystic component. 5.12). Ileocecal region involvement leads to ileocecal A rare immunocompetent patient develops valve enlargement. primary cytomegalovirus colitis, followed by Computed tomography of abdominopelvic ulcerative colitis, raising the possibility of actinomycosis reveals concentric or eccentric cytomegalovirus infection triggering the onset bowel wall thickening of varying contrast of ulcerative colitis. enhancement, together with a heterogeneously enhancing tumor adjacent to involved bowel Typhlitis/Neutropenic Colitis (71). At times an abscess is in the differential diagnosis. Progression over time tends to be Typhlitis is not a specific disease but a descrip- gradual, raising further suspicion for cancer. As tive term of cecal inflammation. The term was one example, a barium enema in a patient more in vogue at the beginning of the 20th revealed a tumor at the base of the and a century, prior to appendicitis being identified as narrowed , whereas CT identified a separate entity. Currently the term typhlitis a mass in the ileocecal region (72); 7 months is reserved mostly for a primarily neutropenic later adjacent tissues were more infiltrated, the cecal infiltration developing in a setting of acute cecum more involved, the sigmoid colon further leukemia, lymphoma, aplastic anemia, and narrowed, and pelvic extension identified. A other immunologic deficiency conditions. pelvic abscess and appendiceal carcinoma were Neutropenic colitis is common in immuno- in the differential diagnosis. Laparotomy and compromised neutropenia patients, most histology revealed chronic inflammation involv- often in patients with hematologic malignan- ing the ileocecal region, right ureter, fallopian cies, transplant patients, and those with AIDS. tube, ovary, bladder, psoas muscle, and abdom- A viral organism is isolated in some, with inal wall, and confirmed the underlying actino- cytomegalovirus predominating. Superimposed 210

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A B

Figure 5.12. Cytomegalovirus colitis. A,B: Two pelvic CT images reveal a dilated, thick-walled colon (arrows). Pseudomembranous colitis is in the differential diagnosis. (Courtesy of Patrick Fultz, M.D., University of Rochester.)

focal ischemia and infection result in bowel nutrition, immunodeficiency, and colonic stasis, wall inflammation and, if severe enough, necro- especially in fragile elderly patients, result in sis. The differential diagnosis often includes high morbidity and mortality. primary infection and neoplastic infiltration. Numerous antibiotics and other drugs are Imaging reveals cecal wall thickening extend- responsible for this condition. Antitumoral ing for varying lengths into the ascending colon. agents induce a pseudomembranous colitis,pre- Lumen distention is an inconsistent finding. sumably due to their combination antimitotic Often CT detects a hypodense cecal wall due to and antibacterial activity. 5-Fluorouracil often edema. Surrounding inflammation, fat strand- results in a mild, nonspecific colitis but rarely ing, and pericolonic fluid are common. leads to florid pseudomembranous colitis.Inter- feron occasionally results in an acute colitis similar to inflammatory bowel disease. Toxin- Drug-Related Colitis producing strains of the anaerobic bacterium C. difficile are implicated in almost all instances, Classification of some of the following condi- although rarely Staphylococcus aureus, Clostrid- tions is arbitrary. Ischemia is often the final end ium perfringens, Yersinia enterocolitica, and point. some strains of salmonella and shigella are involved. Rarely, more than one organism is involved. Antibiotic-Associated Pathogenesis consists of the replacement of (Pseudomembranous) Colitis normal colonic bacterial flora by C. difficile with Clinical release of mucosal toxins. Damage is secondary to at least two toxins: an enterotoxin (toxin A), Whether the term antibiotic-associated colitis or which induces intestinal tissue damage and pseudomembranous colitis is used is a personal fluid response, and a cytotoxin (toxin B), which choice; some authors simply label this condition produces an in vivo additive effect. A fast and Clostridium difficile diarrhea. A pseudomem- inexpensive enzyme-linked immunosorbent brane is not always identified; then again, an assay (ELISA) test for the enterotoxin is avail- occasional adult develops pseudomembranous able, although it is not foolproof. Also, an anti- colitis, even a fulminant one, without recent body response to these toxins is detected in antibiotic therapy. A similar condition was some asymptomatic carriers. already recognized in the preantibiotic era Complicating the picture is a wide spectrum when it was encountered mostly after surgery of clinical presentations ranging from an asym- and manifested as an . Associated mal- ptomatic carrier to a fulminant, life-threatening 211

COLON AND RECTUM toxic megacolon-like condition. Findings are most evident in the colon, although more exten- sive bowel involvement develops in some patients. Clinically, colitis with fever, elevated erythrocyte sedimentation rate, and elevated white cell count are common. An experienced observer can suggest the diagnosis during sigmoidoscopy. Biopsy of characteristic plaques confirms the diagnosis. One should avoid making a diagnosis of antibiotic-associated colitis based solely on stool culture for C. difficile; asymptomatic car- riers exist both in adults and neonates, espe- cially in hospitals. Figure 5.13. Clostridium difficile colitis. CT reveals circumferen- In spite of adequate medical management, tial colonic and rectal wall thicken (arrow). (Courtesy of Patrick some patients progress to toxic megacolon Fultz, M.D., University of Rochester.) and perforation. Occasionally a colectomy is necessary. One novel therapy is formation of a colostomy and instillation of vancomycin through the colostomy. margin with an interposed hypodense sub- mucosa. A number of disorders have a similar abnormal appearance. Although CT can suggest Imaging the diagnosis in the appropriate clinical setting, Conventional radiographs detect only more laboratory findings are more sensitive. At one extreme bowel involvement. A toxic megacolon institution, C. difficile colitis was explicitly diag- appearance is indistinguishable from that seen nosed at CT with a 52% sensitivity and 93% in inflammatory bowel disease. specificity (73). A barium enema is not necessary and is Ultrasonography shows a thickened bowel poorly tolerated by these patients. Performed wall and luminal narrowing. Some patients have early in the course of this condition it shows two concentric bowel wall rings: a thick hetero- multiple small plaques, a shaggy bowel wall geneous hyperechoic inner ring composed of outline, thickened haustra, and bowel wall plaques and mucosal and submucosal edema, thickening. and a thinner hypoechoic outer ring represent- Ascites develops as the condition progresses. ing muscularis propria. Ascites is also found in a number of other Indium-111–labeled leukocyte imaging colitides (except ulcerative colitis), and its pres- identifies bowel activity. 18F-FDG-PET in a ence does not aid in narrowing a differential patient with C. difficile colitis can result in diagnosis. marked 18F-FDG uptake throughout the colon Once pseudomembranous colitis is well wall. established, CT detects nodular haustral thick- ening, thickened colonic wall ranging from seg- Nonsteroidal Antiinflammatory mental to a pancolitis, ascites, and pericolonic Drug Colopathy edema (Fig. 5.13); the markedly serrated lumen identified by conventional radiography has been Nonsteroidal antiinflammatory drugs are asso- called the CT accordion sign. These serrations ciated with a nonspecific colitis. Analgesic sup- should not be confused with deep ulcers or positories cause extensive proctitis, including sinus tracts. One should keep in mind, however, ulcerations. They have been implicated in col- that the accordion sign is not specific for lagenous colitis. They also exacerbate a pre- pseudomembranous colitis and other causes of existing colitis. Pathogenesis of this condition colonic inflammation or edema also result in is unclear, although vascular stenoses and this sign. resultant ischemic are likely causes. Arterial phase CT reveals a target sign,con- These drugs are implicated in erosions and sisting of a hyperdense inner and outer wall colonic ulcers. An occasional patient develops a 212

ADVANCED IMAGING OF THE ABDOMEN benign-appearing colonic stricture, including reflecting repeated cocaine use. When severe, short, diaphragm-like colonic strictures (74). patchy necrosis to the point of perforation and Biopsy reveals cryptitis, fibrosis, and granulo- multiple small vessel thrombi develop. mas, suggesting Crohn’s disease, but the findings clear after drug discontinuation. Colitis Collagenous/Microscopic/ recurs with drug rechallenge. Bloody diarrhea and abdominal pain are and (also typical presentations and, on a more chronic called lymphocytic colitis) are recently recog- basis, weight loss and iron-deficiency anemia nized clinicopathologic conditions, but whether ensue. these are separate entities or variations of a single condition is not clear. Little evidence Cathartic Colitis supports two distinct disorders; the immune abnormalities are similar in both and a similar Cathartic colitis is a term applied to the colonic immune mechanism appears involved. The two findings developing secondary to chronic stim- names reflect their histologic findings. Patho- ulant abuse. Often implicated is chronic genesis of both appears to be either inflamma- ingestion of bisacodyl, phenolphthalein, senna, tory or autoimmune in nature; a role for and casanthranol. Anthranoid laxatives such as infection or drug toxins is speculative. senna (Cassia senna) and cascara (Rhamnus Collagenous/lymphocytic colitis is most purshiana) are commonly used purgatives in often associated with nonsteroidal antiinflam- treating constipation. After passing unabsorbed matory drugs. Underlying rheumatologic and to the colon, they are metabolized to active autoimmune diseases are often present; even aglycones, which act as laxatives by damaging celiac disease exists in some patients. Some epithelial cells, thus affecting normal absorp- patients have associated gastric and duodenal tion, secretion, and bowel motility. Damaged subepithelial collagenous deposits or Crosby epithelial cells eventually produce a pigmented capsule biopsy evident but subclinical small mucosal, called (pseudo)melanosis coli. This intestinal abnormalities. A possible patho- pigmentation gradually disappears after genetic association between interstitial cystitis drug cessation. When detected endoscopically, and collagenous colitis has been raised. This melanosis coli usually implies chronic anthra- condition may not be limited to the noid laxative abuse, although melanosis coli has colon. also been described in patients with chronic Biopsies in both collagenous and lympho- inflammatory bowel disease (75). cytic colitis reveal intraepithelial lymphocytes, Previous studies suggested that anthranoid probably a reflection of epithelial injury, and a laxative use and resultant melanosis coli is lamina propria plasma cell and neutrophil tumorigenic, and these patients are at increased infiltrate. In collagenous colitis a thickened col- risk for , but a more recent lagen band is evident beneath the surface prospective study found no significant risk for epithelium, a finding missing in microscopic either colorectal adenomas or carcinomas (76). colitis. In an occasional patient microscopic Colonic redundancy and dilation are com- colitis progresses to collagenous colitis. mon in patients with chronic constipation, but Symptoms in patients with collagenous loss of haustral folds is found only in those colitis tend to be nonspecific, with chronic taking laxatives. watery diarrhea and abdominal pain predomi- nating. Most patients are women in their sixth Cocaine Colitis decade or older.Most patients have spontaneous or treatment-related resolution of their symp- Cocaine colitis is considered a form of ischemic toms. One unusual association was salmonella colitis. Left colon lesions predominate and osteomyelitis developing in a patient with col- consist of ulcers, hemorrhagic, edematous lagenous colitis (77). mucosa, and inflammatory polyps; rectal A barium enema or endoscopy reveals no involvement is common, an unusual finding specific abnormality in most patients. In a with classic ischemic colitis. Histologically, minority macroscopic erosions and even ulcer- lesions range from acute to chronic, probably ations are evident. Endoscopic findings also 213

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include edema, erythema, and an abnormal images, and enhanced slightly after gadolinium vascular pattern (78). The diagnosis rests on (79); the authors postulated that intracytoplas- histopathologic findings. mic siderocalcific inclusions accounted for the CT and MRI findings. Diversion Colitis Other Colitides After surgical bowel diversion and formation of an excluded segment, some patients develop A barium enema should be diagnostic of colitis inflammatory changes in the diverted bowel. cystica profunda. If large enough, the fluid-filled These consist of aphthae, crypt abscesses, and cysts are also visible with CT or endorectal US easy friability. Large ulcerations develop in an (if the rectum is involved). occasional patient. Occasional reports describe a hot-water enema or some chemical inducing colitis Malacoplakia (Fig. 5.14). Xanthogranulomatous inflammation of the Colonic malacoplakia is rare, occurring both in sigmoid colon has led to colonic obstruction. isolation and in association with other diseases. Kawasaki disease (mucocutaneous lymph Although not a neoplasm, malacoplakia is node syndrome) in a child can present with locally aggressive and invades surrounding fever and focal colitis. tissues. At times it is multifocal. Kidney trans- plant patients, in particular, appear prone to develop colorectal malacoplakia; in some, mala- Neonatal Necrotizing Enterocolitis coplakia appears related to immunosuppression Clinical therapy. It has developed in a colon adenoma, although more often it is associated with a car- A disease more common in premature neonates, cinoma, where malacoplakia is located adjacent necrotizing enterocolitis (NEC) typically starts to the tumor. with bloody diarrhea or distention several Rare clinical manifestations of malacop- days after birth. Although a number of factors lakia include massive hemorrhage and cecal have been postulated, epidemic outbreaks in perforation. newborn nurseries implicate an infectious role. Imaging usually suggests a malignancy. Some The final common pathway is probably ischemia develop multiple polyps. Malacoplakia in one with subsequent mucosal or more severe patient was hyperdense on unenhanced CT, damage. A condition similar to neonatal NEC hypointense both on T1- and T2-weighted MR occasionally develops in older infants. Many

A B Figure 5.14. Chemical-induced colitis in a patient who was giving herself hydrogen peroxide enemas for constipation.A,B: CT shows marked rectosigmoid wall thickening (arrows). (Courtesy of Thomas Miller, M.D., San Luis Obispo, California.) 214

ADVANCED IMAGING OF THE ABDOMEN have had prior major surgery, and underlying horizontal-beam radiographs are necessary to ischemia appears to be a factor. detect a subtle perforation. Perforation, or Necrotizing enterocolitis carries a high mor- impending perforation, is an indication for tality, averaging 50% in some centers, with mor- surgery. tality varying inversely with gestational age and A contrast enema is usually not performed birth weight. Extensive bowel resection may during the acute episode because of a perceived result in a short gut syndrome. increased risk of perforation.Most strictures are detected with a barium enema later, after the Imaging acute insult has resolved. An occasional sequela is an enteroenteric or enterocolic fistula. Any part of the bowel can be involved, although If an ileostomy or colostomy is necessary, the most common sites are distal small bowel study of the distal colon is worthwhile prior to and proximal colon. Involvement ranges from ostomy takedown to ensure that no residual diffuse to segmental.Among neonates undergo- strictures exist. ing surgery, about a third have NEC totalis (80). Strictures,usually colonic,and more often in the left colon, develop as a late complication. Ischemic Colitis Conventional radiography early in the course Clinical of NEC reveals small bowel dilation, then colonic distention. In some neonates focal Bowel ischemia and various vasculitides are dis- regions of bowel lumen narrowing and wall cussed in more detail in Chapter 17. Isolated thickening are evident, nonspecific findings. colonic ischemia is relatively common, espe- Eventually and portal cially in the elderly, and its clinical and imag- venous gas develop in some, findings almost ing manifestations are sufficiently discrete to pathognomonic for NEC in neonates (it is a gas warrant separate discussion. Colon ischemia is and not air as some of the literature claims). often included under the colitides. Especially Although in adults portal venous gas carries a when chronic in nature, ischemic colitis and grave connotation, in these neonates such gas some of the vasculitides tend to mimic represents a more benign finding. Complicating inflammatory bowel disease. Some of the condi- the picture, some babies even with severe NEC tions associated with colonic ischemia are listed do not develop pneumatosis or portal venous in Table 5.3. gas. Ascites is usually a sign of severe NEC, a A typical clinical presentation is sudden onset finding difficult to detect with conventional of abdominal pain, distention, and bloody radiography but readily apparent with US. maroon-colored diarrhea. Atypical presenta- Although these findings are useful as a guide, tions are relatively common; in a study of they are insensitive in predicting impending patients with eventually proven ischemic colitis, perforation. ischemia was initially not suspected clinically in In neonates with NEC and portal venous gas, 30% (82). Underlying atherosclerosis, shock, venous gas developed within 24 hours of onset and congestive heart failure are common but of abdominal distention, feeding intolerance, or not universal findings in these often elderly a finding of rectal blood (80); pneumatosis patients. Sequelae range from a mild, self- intestinalis was identified in 80%, and 20% pro- limiting condition to major gressed to perforation. Venous gas initially was and death. transient but recurred in some of these Most common sites for colonic ischemia are neonates. at the splenic flexure and sigmoid.At the splenic Urine CT attenuation is increased after flexure a branch of the middle colic artery forms enteral iohexol in neonates with NEC; in normal an anastomosis with an ascending branch of the neonates urine CT attenuation is slightly above inferior mesenteric artery, feeding the marginal water. A serial increase in urine CT attenuation artery of Drummond. This marginal artery is coefficients after oral ingestion of iohexol is present in less than half the population; the associated with clinical deterioration (81). tenuous splenic flexure blood supply only Complications of NEC include perforation, becomes worse with onset of arteriosclerotic often early in the course. Serial conventional disease. 215

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Table 5.3. Conditions associated with ischemic colitis prevalence is about 1% to 5%, mostly in elderly Arteriosclerotic patients. The most common cause of associated Venous thrombosis obstruction is a carcinoma, less often a benign Low flow states (hypotension, stasis) stricture or diverticulitis; the ischemic segment Emboli appears thickened, ulcerated, or even necrotic. Atherosclerotic emboli At times pneumatosis is evident. Untreated, Cholesterol emboli perforation ensues. Vasculitides Behçet’s syndrome Cocaine-use colitis Imaging Polycythemia in a smoker Polycythemia vera and extensive extramedullary The role of imaging during an acute ischemic hematopoiesis attack is to confirm that a patient’s symptoms Takayasu’s arteritis are indeed due to colon ischemia rather than to Thromboangiitis obliterans (Bürger’s disease) another etiology. Angiography has a lesser role Systemic lupus erythematosus in detecting colon ischemia than in the past. Polyarteritis nodosa Often identified is atheromatous disease involv- Dermatomyositis ing major vessels. Allergic granulomatous vasculitis (Churg-Strauss Imaging findings during the acute phase syndrome) consist of bowel wall thickening, seen as Other Associated with oral contraceptives thumbprinting, and ulcerations, eventually Massive caustic ingestion clearing or evolving into strictures or frank A late complication of hemolytic-uremic syndrome necrosis. An ischemic segment tends to have Familial dysautonomia (Riley-Day syndrome) sharp margins, in distinction to most acute During a-interferon therapy infective colitides, which have poorly defined margins. Computed tomography readily identifies colonic wall thickening; pericolonic stranding is common but is nonspecific. Occa- sionally seen is a “halo” sign, consisting of an inner hypodense ring surrounded by a hyper- Isolated rectosigmoid ischemia is uncom- dense outer ring, a nonspecific sign also found mon, presumably because of collateral blood in some other colitides. supply. Occasionally sigmoid colectomy leads to Computed tomography reveals the involved rectal infarction; presumably the superior rectal colonic wall to range from a heterogeneous arteries, which are sacrificed at resection, appearance suggesting edema in about two provide major rectal blood flow. thirds and homogeneous thickening in one Colonic infarction in one patient led to tran- third, with occasional intramural gas; wall sient gastric emphysema (83). thickening and segmental involvement are Ischemia after hemorrhagic shock is more common. common in the small bowel than colon. In the Isolated cecal ischemia or infarction is rare. large bowel, the right colon is most often Clinically, appendicitis is suspected but CT involved, even to the point of ischemic necrosis. should differentiate these two entities. Resection in some of these patients reveals no Doppler US aids in differentiating between vascular thrombi or emboli, and nonocclusive inflammation and ischemia of thickened bowel ischemia is presumably responsible. wall. The absence of color Doppler flow and A type of ischemic colitis warranting separate absence of arterial signal suggests ischemia; in mention is that occurring proximal to a colonic fact, the absence of arterial flow in the wall of an obstruction. Also called obstructive colitis,it is ischemic colon predicts an unfavorable outcome similar to inflammatory bowel disease.Ischemia (84). in this condition is due to an impaired venous In-111–labeled leukocyte imaging detects blood flow secondary to a combination of bowel activity in ischemic colitis. Normally In- increased endoluminal pressure, underlying 111 activity is not identified in bowel.A primary atherosclerotic disease that otherwise would be purpose of Tc-99m-HMPAO leukocyte scan is to asymptomatic, and other possible factors. The detect inflammation rather ischemia, but in an 216

ADVANCED IMAGING OF THE ABDOMEN occasional patient, this scan reveals marked Amyloidosis uptake within an ischemic sigmoid colon. Conventional radiography in three patients Amyloidosis ranges from localized to diffuse revealed vascular calcifications close to the involvement. When localized, amyloidosis often right hemicolon, a barium enema showed mimics a benign stricture, rarely, a carcinoma thumbprinting and right colic lumen narrow- (87). It does not predispose to cancer formation; ing, and CT detected colon wall thickening and a finding of localized amyloidosis and a coexis- venous calcifications (85); the authors termed tent carcinoma is probably fortuitous. Colonic this condition phlebosclerotic colitis. amyloidosis does ulcerate and bleed; presum- ably blood vessel wall infiltration by amyloid leads to ischemia and ulceration. Radiation Proctocolitis Radiation proctocolitis is a disabling, often Epiploic Appendagitis delayed manifestation of radiation injury and results in an obliterative endarteritis and Appendices epiploicae are mostly fat-containing ischemia. Because of its proximity to gyneco- structures arising from colonic serosal surface. logic structures, the rectum is a common site of They exist throughout the colon. Normally they involvement. These patients range from asymp- are not detected with imaging except if sur- tomatic to having chronic bleeding, obstruction rounded by fluid. due to strictures, or fistulas. Bleeding typically The sudden onset of localized acute abdomi- develops months after completion of radiation nal pain is a common presentation for torsion therapy. Before ascribing rectal bleeding to (infarction) of an epiploic . These proctitis, however, other causes of gastrointesti- patients are afebrile, and laboratory findings are nal bleeding should be excluded in these normal. Depending on the location, clinically patients. and with imaging the condition mimics acute Computed tomography findings following appendicitis or diverticulitis. Although epiploic radiation therapy vary. Detected are perirectal appendagitis is a nonsurgical cause of an acute fascia thickening, increased perirectal fat abdomen, it is not uncommon for the diagnosis density, and, less often, rectal wall swelling. Pre- to be made by either the surgeon or pathologist. sacral space widening develops in a minority, Untreated, spontaneous resolution in a week or increasing with dose. These changes develop so is the usual outcome. soon after start of therapy. Most often epiploic appendagitis occurs in Endorectal US shows thickening of perirectal either the ascending or descending portions of connective tissue and obliteration of the rectal the colon and tends to be located anteriorly submucosal echogenic layer along the anterior rather than posterior in the bowel wall cir- rectal wall (86). cumference (Fig. 5.15). A CT finding of a focal Magnetic resonance imaging identifies radia- inflammatory tumor or edema adjacent to the tion fibrosis as irregular enhancement and high colon, especially at sites uncommon for diverti- signal intensity, often even years later. culitis, should suggest this condition. A fat Clinically significant bleeding from radiation- density or almost fat density tumor is a induced proctitis has been managed suc- common but not universal finding. Computed cessfully using a combination of endoscopic tomography in six patients identified a fatty yttrium-aluminum-garnet (YAG) laser therapy tumor containing a hyperdense rim along the and application of topical formalin dressings to anterolateral colonic wall, together with infiltra- the rectal mucosa. tion of adjacent pericolic fat (88). The risk for future neoplasms with chronic Ultrasonography often reveals a small, solid, radiation proctocolitis, even decades after focal noncompressible hyperechoic tumor at the pelvic radiation, is well known to most physi- site of maximum tenderness. cians. Both flat (nonpolypoid) adenomas and Computed tomography and US findings are rectal carcinomas develop. Imaging is not reli- strongly suggestive of the diagnosis. Similar able in detecting small neoplasms in the pres- findings are seen with segmental omental ence of radiation changes. infarction, although usually these are in a dif- 217

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Nonneoplastic Tumors Hyperplastic Polyps Small hyperplastic polyps (also called meta- plastic polyps) are the most common nonneo- plastic lesion in the colon and rectum. They tend to be sessile, often are multiple, generally <5mm in diameter, and most commonly in the rectosigmoid. A relationship between hyperplastic polyps and the subsequent development of adenomas is controversial. Both share similar lifestyle risk factors. Most colonic hyperplastic polyps are not considered to have a neoplastic potential Figure 5.15. Epiploic appendagitis. A barium enema reveals and are not directly involved in the adenoma- focal extravasation (arrow). The appearance is atypical for carcinoma cycle, but some larger hyperplastic diverticulitis. polyps do develop dysplasia and progress to a cancer. An occasional patient with multiple hyperplastic colonic polyps harbors a colon ferent location. In either case, therapy is similar adenocarcinoma. In addition, follow-up of and surgery is avoided if the condition is patients who had hyperplastic polyps suggests suspected. that they are more likely to develop adenomas Follow-up CT shows resolution of inflam- than those without initial polyps (90). An mation, and although a lesion may still be iden- occasional hereditary nonpolyposis colorectal tified, it should be decreasing in size (88). An cancer family patient develops colorectal occasional infarcted epiploic appendage eventu- cancers, adenomas, and hyperplastic polyps. ally calcifies; some become detached and float The radiologic and endoscopic appearance within the peritoneal cavity. One such peri- of adenomas and hyperplastic polyps <5mm toneal loose body measured 6cm in diameter in diameter is similar. A central umbilication (89). The differential diagnosis of calcified peri- tends to develop with further growth. Some of toneal loose bodies includes lost these small umbilicated tumors, at times called during surgery and, unless their mobility is con- inverted hyperplastic polyps by pathologists, are firmed by imaging with different patient posi- difficult to detect even with a double-contrast tioning, a calcified leiomyoma or similar tumor. barium enema and mimic the appearance of a flat adenoma and adenocarcinoma (91), and Tumors thus excision is warranted. Rare instances of hyperplastic polyposis have A polyp is an intraluminal growth. It can be been reported. These polyps tend to be larger benign or malignant, neoplastic, inflammatory, than isolated ones and the overall appearance or hyperplastic. It is a descriptive term having a mimics multiple adenomatous polyps. Compli- specific morphologic meaning and does not cating the picture is the occasional patient with imply a particular histologic connotation. The hyperplastic polyposis but with some of the practice of some authors in using this term polyps containing foci of adenomatous tissue or synonymously for an adenoma only leads to even an adenocarcinoma. confusion and should be condemned. 18F-fluoro-deoxy-D-glucose PET is negative Among colonic polyps <5mm in diameter, for hyperplastic polyps; FDG does not accumu- in adults, about 40% to 50% are adenomatous, late in these polyps. 40% hyperplastic, and the rest a mix of mucosal tags, lymphoid tissue, and other benign causes. Juvenile Polyp About half are located in the rectosigmoid. In children juvenile polyps predominate. In adults, This polyp is known as a retention polyp, and it the percent of adenomatous and carcinomatous consists of inflammatory tissue, fibrosis, and a polyps increases with an increase in polyp size. cystic component. No consensus exists about 218

ADVANCED IMAGING OF THE ABDOMEN whether it is inflammatory or hamartomatous in origin. It is the most common colonic polyp in the pediatric age group, although some are first detected in adults. It is more common in the distal colon and rectum, and most are solitary. A juvenile polyposis syndrome is rare. Juvenile polyps are not believed to be pre- malignant; polypectomy of a solitary juvenile polyp does not predispose to future new juve- nile polyps and is not associated with a future increased risk of colorectal cancer.Nevertheless, occasional reports describe both an adenoma and an adenocarcinoma associated with juve- nile polyps. Especially in children, a not uncommon presentation is . An occasional juvenile polyp intussuscepts. The polyps’ barium enema appearance is similar to that of an adenomatous polyp. Most Figure 5.16. Inflammatory fibrous polyp (arrows and arrow- have a smooth and oval outline. Compression heads) in a man with rectal bleeding. Initially a carcinoma was gray-scale US shows them to be hypoechoic, suspected. contain small cysts and have an adjacent hyper- echoic layer corresponding to the submucosa (92); their color Doppler findings range from These tumors tend to invade and require hypo- to hypervascular. resection with wide margins.

Hamartoma Inflammatory Fibroid Polyp Retrorectal hamartomas consist of soft tissue Inflammatory fibroid polyps are uncommon in and cysts lined by ciliated epithelium. Also the colon. Some are found in a setting of inflam- called tail-gut syndrome, they are detected due matory bowel disease or chronic infections. to their mass-like effect, and occasionally one Most manifest through rectal bleeding. Biopsy becomes infected. simply reveals inflammation. Similar to an inflammatory pseudotumor, their appearance on a barium enema or Hemangioma colonoscopy suggests a malignancy. They range Colon hemangiomas range in size from small, from a sessile, plaque-like, to a pedunculated focal submucosal lesions to large, diffuse, polyp in appearance (Fig. 5.16). infiltrating tumors involving long colonic seg- ments. Most manifest through chronic bleeding and anemia. Even when large, lumen obstruc- Inflammatory Pseudotumor tion is rare with a hemangioma (Fig. 5.17). (Fibrosarcoma) The full extent of a large hemangioma is eval- uated by contrast-enhanced CT or MRI. Rectal An occasional resected polyp or infiltrating cavernous hemangiomas and their surrounding tumor is termed an inflammatory pseudotumor structures are best evaluated by MRI using an (variously called inflammatory fibrosarcoma or endorectal surface coil. These often diffuse rec- plasma cell granuloma). These tumors are dis- tosigmoid cavernous hemangiomas produce cussed in more detail in Chapter 14. They orig- colonic wall thickening and a hyperintense inate either in the colon or adjacent soft tissues, signal on T2-weighted MR images. including presacral space. Their aggressive Occasionally a hemangioma is detected with nature often suggests a malignancy. a Tc-99m–red blood cell scan. 219

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Lymphangioma Cystic lymphangiomas are more common in the mesentery but do occur in the bowel wall. Ultrasonography reveals these lymphangioma to be compressible, anechoic, and possessing posterior acoustic enhancement; as expected, Doppler US identifies no flow. Computed tomography attenuation is near that of water. Endoscopic US reveals septa in the multilocular ones. A double-contrast barium enema identifies a lymphangioma as a submucosal tumor, soft, round, and smooth. Endometriosis Colonic endometriosis is discussed here in the tumor section because its appearance often mimics a neoplasm. Endometriosis signifies the presence of func- tioning endometrial tissue in ectopic sites. The most common site of intestinal involvement Figure 5.17. hemangioma (arrows). This pliable tumor mimicked a spastic colonic segment but it would is the anterior rectal region, followed by the never distend.No obstruction was present,a typical finding even appendix and ileocecal region. Endometriosis with a large hemangioma. involving the rectovaginal septum posteriorly and then extending laterally into the uterosacral ligaments and anterior rectal wall results in fibrosis and scarring, eventually leading to a colorectal stricture and obstructive symptoms. Perforation and an acute abdomen are rare Lymphoid Nodules complications. This tissue undergoes change under hor- Lymphonodular hyperplasia is quite common monal stimulation.In symptomatic women pain in children and is occasionally encountered in and altered bowel habits are common presenta- adults. The condition occurs both in the small tions. Clinically, endometriosis often mimics bowel and colon. An association between lym- inflammatory bowel disease. phonodular hyperplasia and several disorders Colonoscopy reveals intact mucosa at the site has been described, although currently most of involvement; mucosal ulcerations occur in a investigators believe that in some patients, espe- minority and are a cause of rectal bleeding. At cially children, the presence of lymphonodular times only laparoscopy establishes the diagno- hyperplasia is a normal variant. It is found adja- sis. With typical anterior rectal wall involve- cent to a colonic segment involved by ulcerative ment, barium enema findings are similar to colitis, and the presence of these nodules was those seen with rectal invasion by a gynecologic proposed as a sign of early ulcerative colitis tumor (Fig. 5.18) or metastasis to the pouch of (93). Such lymphoid hyperplasia also develops Douglas. in posttransplant patients who are under Endorectal US achieved a sensitivity and chronic immunosuppression. specificity of over 95% in detecting rectovaginal These small polyps, up to several millime- septal infiltration by endometriosis (94). ters in diameter, are readily detected by Although these results are impressive,the role of both a double-contrast barium enema and US in providing a differential diagnosis and colonoscopy. Rarely, enough lymphoid tissue aiding management is not clear. accumulates at one site to result in a larger Magnetic resonance imaging reveals lymphoid polyp. endometriosis >1cm in size to be homoge- 220

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A B

Figure 5.18. A,B: Two women with rectal endometriosis (arrows) identified on lateral barium enema views. The focal, corrugated, anterior rectal wall involvement is typical. A gynecologic cancer growing posteriorly into the rectal serosa has a similar appearance.

neously hyperintense on T1-weighted images wall excision and partial rectal resection are and hypointense on T2-weighted images; necessary. smaller lesions tend toward a variable T2- weighted signal (95). Some foci contain a cystic Xanthelasma component (Fig. 5.19). Surgery for rectosigmoid endometriosis is Xanthelasma is diagnosed histologically as a technically difficult. At times posterior vaginal collection of lipid-laden histiocytes. It develops

A B

Figure 5.19. Endometriosis involving pouch of Douglas. Sagittal (A) and transverse (B) T2–weighted magnetic resonance (MR) images reveal a heterogeneous tumor between the uterus and rectum (arrows), illustrating how the anterior rectal wall is so often involved. (From Burgener FA, Meyers SP,Tan RK, Zaunbauer W. Differential Diagnosis in Magnetic Resonance Imaging. Stuttgart: Thieme, 2002, with permission.) 221

COLON AND RECTUM in the colonic wall and other structures. convoluted surface or residual oral contrast in Imaging plays no role in this condition. polyp interstices (96). Detection of one adenoma implies an increased future risk for another adenoma. Benign Neoplasms Studies provide somewhat conflicting results, Adenoma but, in general, among patients followed for at least 10 years, those with a large initial adenoma The primary importance of colon adenomas have a significantly higher risk of developing is in their potential for carcinomatous trans- metachronous adenomas. formation. Less often they manifest by bleeding or other complications. More adenomas are detected in the left colon than the right, Leiomyoma although over the last several decades a shift Colorectal leiomyomas are uncommon. Most toward right-sided polyps is evident, especially are asymptomatic, although the larger ones tend in African Americans; in this patient population to be associated with pain, change in bowel the malignancy potential for right-sided polyps habits, or rectal bleeding. Some are detected is similar to that found on the left. incidentally during a . Most small adenomas are tubular or tubu- Leiomyosarcomas tend to be larger and more lovillous, and a small minority are villous. A inhomogeneous than leiomyomas. larger villous component within an adenoma is Endorectal US reveals rectal leiomyomas as associated with a higher risk for high-grade dys- hypoechoic tumors, similar to other stromal plasia and cancer. Villous adenomas are gener- tumors. It is helpful in evaluating tumor ex- ally excised because even multiple biopsies may tent, but not in differentiating benign from miss a focus of carcinoma. Some villous adeno- malignant. mas, however, are treated with endoscopic neodymium (Nd):YAG laser therapy, and one must ensure adequate therapy; incompletely Lipoma treated ones recur. Complications of laser therapy include stricture, self-limited bleeding, Lipomas are intramural in origin and most are and fistula. single, although diffuse colonic lipomatosis Some villous adenomas regress after non- does occur. They vary in size considerably. More steroidal antiinflammatory drug therapy. often than other stromal tumors, lipomas tend The role of Helicobacter pylori infection in to become pedunculated and act as a lead point colon adenoma and carcinoma formation is not for an intussusception. Some lipomas undergo clear. Prevalence of H. pylori antibodies in spontaneous autoamputation. patients with colorectal adenomas and carcino- Uncomplicated lipomas have a CT fat density. mas is greater than in controls. Intussuscepting ones tend to contain more of a Adenomas range from pedunculated to soft tissue density, probably because of associ- sessile. Some have a long stalk, in others a stalk ated infarction and necrosis. The lack of fat is barely visible. Sessile adenomas range from detected by CT in the lead point of an intussus- those with a discrete intraluminal component ception thus does not exclude a lipoma. to relatively rare flat ones, with the latter Endoscopic US identifies colon lipomas as consisting of an intramural tumor with a hyperechoic tumors. nodular or reticular surface and thus being Magnetic resonance imaging reveals lipomas especially difficult to detect either by imaging as typical fat-density tumors—hyperintense on or endoscopy. Villous adenomas are classically T1- and hypointense on fat-suppressed T1- described as frond-like and containing numer- weighted images. ous interstices, but such an appearance in found only in a minority. Imaging cannot differentiate Angiomyolipoma most villous adenomas from their tubular counterpart. Extrarenal angiomyolipomas are rare. If large Computed tomography suggested several enough, an ileocecal valve angiomyolipoma or anecdotal villous adenomas by identifying a one in the left colon can obstruct. 222

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Polyposis Syndromes those with <1000 polyps (99); each 10-year age group led to a 2.4-fold difference in cancer risk. Not all patients with familial polyposis can be Nevertheless, occasional cancers are detected in placed in a discrete syndrome. Thus one large patients younger than 30 years of age and those family had a tendency to develop mixed colonic having less than 1000 polyps. adenomatous and hyperplastic polyps, with the A predisposition to adenomatous polyps in characteristic lesion being an atypical juvenile familial adenomatous polyposis is best known, polyp, although some polyps contained mixed but both benign and malignant tumors also histology (97); some of these polyps became develop at other sites. More common extra- malignant. Inheritance in this family appeared colonic manifestations include desmoid tumors, to be autosomal dominant. often extraperitoneal in location, and gastro- duodenal neoplasms. These patients tend to Familial Adenomatous Polyposis have gastric fundic gland polyposis. Skin, sub- cutaneous tissue, and bone tumors develop. Familial adenomatous polyposis is a genetic Some studies suggests an increase in adrenal disorder with an autosomal-dominant inheri- tumors. Papillary thyroid carcinoma are tance and penetrance approaching 100%. detected in about 1% to 2% of these patients. Typically these patients develop hundreds to Colon polyps develop and start growing thousands of adenomatous polyps throughout roughly at the time of puberty, and in patients the colon and often also in the rest of the gas- at known risk surveillance is started shortly trointestinal tract. Gardner’s syndrome and thereafter. A double-contrast barium enema familial polyposis coli have the same genetic readily detects familial polyposis, although defect but exhibit different phenotypic expres- most gastroenterologists perform endoscopy. sion. Many investigators describe both entities The nonsteroidal antiinflammatory drug with the term familial adenomatous polyposis. sulindac is currently used to treat patients with The Swedish Polyposis Registry noted an familial polyposis. Long-term use leads to a incidence rate during 1977 to 1996 of 0.86 per marked reduction in the number and size of million and a prevalence 32 per million at the polyps and, at times, even in their disappear- end of 1996 (98); the median age at polyposis ance. Occasionally, however, polyps recur and a diagnosis of probands was 39 years, while in the malignancy develops. call-up group it was 22 years. Importance of Because the predominant risk in many of earlier detection is evident: 67% of probands these patients is colon cancer, colon resection is and 3% of call-up patients already had colo- recommended. Procedures performed include rectal cancer at initial diagnosis, with corre- the following: sponding mortality rated being 44% and 2%, respectively. 1. Proctocolectomy with ileostomy The discovery of a defective gene changed the 2. Total colectomy with ileorectal anastomo- diagnosis of this condition and now allows sis and postoperative rectal surveillance direct carrier identification by mutation 3. Colectomy, rectal mucosectomy, and ileo- screening in some but not all patients. The rectal pull-through (ileal pouch) mutation abnormality is complex, and numer- ous mutations in the adenomatous polyposis Unsatisfactory results with proctocolectomy coli gene have been identified. The defective and ileostomy led surgeons to a total colectomy gene is a tumor suppressor gene having a role with an ileorectal anastomosis, but an intact in carcinogenesis. Although gene mutations rectal mucosa leaves these patients at risk for are often evident in sporadic colorectal adeno- developing a future rectal carcinoma. In a Czech mas and carcinomas, familial adenomatous study of 55 patients undergoing colectomy and polyposis patients already have mutations in ileorectal anastomosis for familial polyposis, this gene. 16% developed a malignant tumor within 16 Polyp count and age are directly related to the years (100). Many of these patients have either risk of cancer. Patients with >1000 polyps had a nodal or distant metastases at the time of 2.3 times greater risk of having a cancer than rectal cancer detection, and a number of studies 223

COLON AND RECTUM have concluded that a proctocolectomy and patients with familial adenomatous polyposis ileoanal anastomosis should be the primary are still from colorectal cancer (102); the operation, instead of colectomy and ileorectal proportion of deaths caused by extracolonic anastomosis. disease is rising, however, probably due to better The Soave procedure—a colectomy, rectal screening and earlier prophylactic colectomies. mucosectomy, and ileorectal pull-through—is Desmoid tumors are especially difficult to currently preferred by many surgeons. One manage. Death due to desmoid tumor compli- unanswered question concerns therapy when cations is not uncommon. small bowel polyps are present. Also, these patients are at increased risk of developing ileal pouch polyps. Among 85 ileal pouches Turcot’s Syndrome examined, 35% contained adenomas (101); Turcot’s syndrome is a rare hereditary disorder the risk of developing an adenoma at 5, 10, consisting of central nervous system malignant and 15 years was estimated to be 7%, 35%, gliomas and colon polyposis. It has manifested and 75%, respectively. Those with a pouch in the pediatric age group. adenoma were more likely to also have duode- In a 30-year-old Japanese man with nal adenomas. histopathologically confirmed glioblastoma Complications of an ileorectal Soave pull- multiforme and colonic well-differentiated ade- through include anastomotic stricture and nocarcinoma, somatic mutations of K-ras and leak. Some of these strictures are dilated using APC genes were identified in the colon carci- either endoscopic or imaging guidance. Most noma but not in the brain tumor (103); alter- focal perforations heal with time. Although a ations in DNA repair genes presumably play a new ileorectal pull-through is feasible after role in these tumors. breakdown of an initial anastomosis, a number of these patients are left with a permanent ileostomy. Multiple Hamartoma Syndrome As mentioned previously, these patients are at (Cowden’s Disease) increased risk for mesenteric fibromatosis, or desmoid tumors. Some desmoids form sponta- Familial multiple hamartoma syndrome, also neously, although their prevalence increases known as Cowden’s disease, is an autosomal- after surgery. Desmoids are considered benign, dominant condition having high penetrance but they are locally aggressive tumors associ- but variable expressivity. The gene involved, ated with considerably morbidity and mortality. believed to be a tumor suppressor gene, has Desmoids are most common in the mesentery, been mapped to the long arm of chromosome followed by abdominal wall. Abdominal wall 10 at 10q22–23. Mutations in this gene were desmoids can be excised but recur in about half identified in 81% of 37 Cowden’s disease fami- of patients; mesenteric desmoids are more lies (104); these include missense and nonsense difficult to excise. A not uncommon history is point mutations, deletions, and insertions over for a patient to undergo total colectomy, a the entire length of this gene. desmoid tumor develops in the abdominal wall Numerous hamartomatous polyps are the or close to some other surgical incision, a usual gastrointestinal tract manifestation of second surgical procedure is performed to Cowden’s disease. One patient presented with resect the desmoid, a more extensive desmoid numerous round gastric and duodenal polyps recurs, etc. An occasional desmoid becomes and elongated (filiform) small bowel polyps infected and forms an abscess. (105). Extraintestinal manifestations vary At times skeletal scintigraphy with 99mTc- considerably and range from macrocephaly to HDP shows diffuse uptake in regions of various genitourinary defects and other fibromatosis. deformities. Medical therapy is feasible for some desm- Some affected patients develop gastric or oids. Some regress with tamoxifen therapy. colonic carcinomas, although the premalignant Data in the Familial Gastrointestinal Cancer status of these polyps is not established. These Registry in Toronto show that most deaths of patients also form various other cancers; in the 224

ADVANCED IMAGING OF THE ABDOMEN abdomen they are at increased risk for renal cell The coexistence of familial juvenile polyposis carcinoma, neuroendocrine neoplasms, germ and hereditary hemorrhagic telangiectasia has cell tumors, and endometrial neoplasms. been described both sporadically and in fami- lies. An association of colorectal juvenile poly- posis and hereditary spherocytosis has also Peutz-Jeghers Syndrome been raised. Peutz-Jeghers syndrome manifests primarily as A severe form of juvenile polyposis is seen in multiple hamartomatous polyps in the , the first several years of life. Some of these , small bowel, and colon. Patients infants have bloody diarrhea and malabsorp- with this syndrome often develop malabsorp- tion to the point that life cannot be sustained. tion and profound anemia or present with recurrent bouts of small bowel obstruction. Malignant Neoplasms Intussusceptions and even prolapse of a colonic polyp through the anus have been reported. Adenocarcinoma Skin pigmentation is common. Clinical A hamartoma-to-adenoma transition se- quence probably exists, with an increased risk of In North America and Western Europe, colorec- carcinomatous development, although the tal carcinoma ranks second in incidence after cancer risk in these patients is considerably less lung cancer in men and breast carcinoma in than with familial polyposis. women. It is considerably less common in devel- A 16-year-old boy with Peutz-Jeghers syn- oping countries. The incidence is increasing in drome diagnosed at age 8 years developed a Eastern Europe and Japan. Published cancer rectal carcinoid (106). data vary not only among countries but also between university and nonuniversity centers.A number of studies show a correlation between Cronkhite-Canada Syndrome meat consumption and colorectal cancer. Still, this topic remains controversial. A French Cronkhite-Canada syndrome consists of ham- review of available studies concluded, “One artomatous polyposis in the stomach, small cannot state, nor exclude, that meat promotes bowel, and colon in association with alopecia colorectal cancer” (107). and onychodystrophy. It is nonfamilial. Regular ingestion of aspirin or other non- Prior to polyp detection these patients steroidal antiinflammatory drugs decreases the develop changes in taste sensation, dystrophic risk of colorectal cancer, although the length of nails, and alopecia areata, findings suggesting time necessary before a reduction in risk occurs the syndrome during the initial patient con- is debated. tact. is common and leads to Although not common, colorectal cancer hypoproteinemia. does occur in young adults, with case reports Numerous polyps containing foci of describing even patients under 20 years of age. inflammation and cystic regions develop in the Some studies report clinical presentation and stomach and small bowel.Not all of these polyps tumor grade to be similar to that in the older are hamartomatous; these patients also develop population, others report a lower morbidity and adenomatous polyps and thus are at risk for mortality; still others suggest dismal results malignancy. because of advanced stage at diagnosis and an aggressive tumor. Juvenile Polyposis Syndromes An association between Streptococcus bovis bacteremia and the presence of a colon carci- The presence of multiple juvenile polyps sug- noma is well known. The reason for this gests one of the familial juvenile polyposis bacteremia is puzzling, because bowel S. bovis syndromes. Three types have been described: colonization rates in those with colorectal polyps limited to the colon, polyps throughout cancer and controls appear similar (108). A the gastrointestinal tract, and gastric juvenile similar association exists with S. sanguis and polyposis. Some patients appear to be at in- colon cancer,and presumably other streptococci creased risk of developing colon cancer. species also lead to bacteremia in a setting 225

COLON AND RECTUM of a colon carcinoma. Other rarer associations members of families with pathogenic mutations include pericarditis caused by Bacteroides frag- at some of these gene carriers is up to 80%; the ilis, an anaerobic colon organism, and Clostrid- risk of nongastrointestinal cancers is also ium septicum gas gangrene. Liver metastases increased for some of these gene carriers. Thus, may become infected. A rare primary colon car- is an upper urinary tract tumor in a patient cinoma, however, manifests as a primary liver with a hereditary nonpolyposis colorectal abscess without liver metastases. cancer due to a genetic abnormality or due to A migratory thrombophlebitis precedes some chance (110)? gastrointestinal malignancies, including colon At least five genes have been identified as cancer. An occasional necrotizing vasculitis sites of germline mutations associated with serves the same purpose. The Leser-Trelat sign hereditary nonpolyposis colorectal cancer consists of an association of multiple seborrheic syndrome. Considerable data point to the p53 keratoses with an internal malignancy; several gene playing a role in colorectal carcinoma colorectal cancers have been reported as a development. Among adenomas, 8% of those component of the Leser-Trelat sign. A rare as- containing low-grade dysplasia were p53 posi- sociation was increasing body hair growth tive compared to 73% of those containing high- (hypertrichosis lanuginosa) before a rectal grade dysplasia, suggesting a role for the p53 cancer was discovered (109). gene in the transition between adenoma and carcinoma (111), and the observed increase Genetics of p53 expression supports an adenoma– carcinoma sequence. Expression of p53 in One definition of hereditary nonpolyposis colo- nonpolypoid carcinomas argues for another rectal cancer is that at least three relatives carcinogenesis pathway. should be affected, one is a first-degree relative A large Dutch cancer registry found the of the other two, and that at least two successive relative risk of brain tumors in hereditary generations be involved. An autosomal- colorectal cancer patients and their first- dominant inheritance is evident for these hered- degree relatives to be six times greater than that itary cancers, and they are characterized by in the general population (112). The relative life- early age of onset, the predominance of right- time risk for these patients is low, and the sided lesions, and an increased prevalence of authors do not recommend screening for brain synchronous and metachronous neoplasms. tumors. Two subtypes of this syndrome are described: Lynch syndrome I: cancers limited to the Associated Conditions colon and rectum Does a colon polypectomy predict future colo- Lynch syndrome II: similar, but extracolonic rectal cancer occurrence? A Milan colonoscopic cancers also involve the endometrium, polypectomy study of over 1000 patients with ovaries, and stomach adenomatous polyps identified the presence of The true prevalence of hereditary nonpoly- multiple adenomas and high-grade dysplasia as posis colorectal cancer is debated. About 1% to significant predictors of future cancer (113); 2% of patients with colorectal cancer fit a presumably this subgroup of patients benefits definition of hereditary nonpolyposis colorectal from increased surveillance. cancer syndrome, although considerable geo- Prior studies have suggested an association graphic variation in the prevalence of this syn- between gallstones (or cholecystectomy) and drome exists. Because of the high worldwide risk of colon cancer; but more recent prospec- prevalence of colorectal cancer, this is one of tive studies fail to support this association. The the more common if not the most common same conclusions have been reached for previ- inherited neoplasm currently known. The ous gastric surgery for . cumulative risk of colorectal cancer for relatives A three- to eightfold increased risk for colon of patients with a colorectal cancer at or under adenomas and carcinomas exists in patients 45 years begins rising at age 40 years, reaching with acromegaly. Patient with acromegaly also 5% at age 50 and 10% at age 70 years. The develop gastric cancer, pancreatic mucinous lifetime risk of colorectal cancer among cystic tumors and other tumors; the known 226

ADVANCED IMAGING OF THE ABDOMEN tumorigenesis of elevated growth hormone and metachronous colon cancers. Patients with a insulin-like growth factor levels appear to be synchronous adenoma or carcinoma discovered responsible for these neoplasms. at initial presentation are at significantly higher An increased risk of colon cancer probably risk for metachronous adenomas and carcino- exists in patients with a Barrett’s . An mas, compared to those without a synchronous association is also suggested with Zollinger- tumor. Ellison syndrome with its hypergastrinemia; a The interval between first and second cancers significant number of patients with colon carci- ranges from months up to a decade or more. noma have increased serum gastrin levels. Carcinoembryonic antigen (CEA) levels do not aid in detecting a second cancer.

Synchronous Cancers Screening An increased prevalence of synchronous colo- Why screen? To a large extent, colorectal cancer rectal cancers has long been known. A multiin- screening consists of detecting adenomas, with stitutional database of 4878 colon cancer a reduction of colon cancer mortality achieved patients recorded 3.3% having synchronous by resecting these precancerous adenomas. tumors (114); of these, 8% had more than two Among colorectal cancers detected by screening tumors at the time of diagnosis. An occasional asymptomatic individuals at one Japanese patient with multiple synchronous colonic ade- institution, 61% were either stage 0 or stage nocarcinomas is reported (115). Considering I; among comparable symptomatic patients the highest stage synchronous tumor, survival only 16% had tumors of these early stages (116). appears to be the same as for patients with a Controversy exists about the size of adeno- single colonic tumor (114). mas that require resection. Should several- Once one colorectal cancer is diagnosed, the millimeter adenomas found at colonoscopy be need to study the remaining colon is known to resected? Also, what is the chance of a malig- most clinicians (Fig. 5.20). Yet, in spite of this, nancy being present in a small colonic polyp some patients still undergo cancer resection (Fig. 5.22)? Histology of polyps not detected by without preoperative study for synchronous a CT colonography study revealed that 58% of lesions. those 5 mm or smaller were not adenomas and A rare patient develops a synchronous colo- 43% of those 6–9mm were not adenomas (117). rectal carcinoma and lymphoma, including An analysis of over 11,000 adenomas detected Hodgkin’s disease; this association appears to be during colonoscopy at the Erlangen Registry of fortuitous. Colorectal Polyps detected no invasive carci- noma in adenomas <5mm (118); the malig- Metachronous Cancers nancy rate for larger adenomas not only showed a right-sided shift but also the rate was The definition of metachronous cancer varies. significantly modified by histology, the presence Most authors use this term to describe a second of synchronous lesions, and other factors. separate cancer, while some also include A Japanese study of sessile colonic adenomas intraluminal recurrences, arguing that a pathol- <5mm followed these polyps for an average of ogist cannot readily differentiate recurrences 24 months (119); none developed carcinoma- from a new focus of adenocarcinoma. tous transformation. The authors concluded Metachronous colorectal neoplasms consist that polypectomy of these small lesions is not of adenomas and carcinomas, related through necessary, and they can be followed either radi- the adenoma-carcinoma cycle (Fig. 5.21). ologically or endoscopically. Patient who have one colorectal cancer resected Colorectal cancer screening has become are at increased risk of developing a second prevalent in the Western world. A survey cancer (metachronous cancer). Overall, the for occult blood, flexible sigmoidoscopy, prevalence of metachronous cancers ranges colonoscopy, and barium enema are the screen- from 1% to 5%, but the prevalence of metachro- ing modalities used. The role of CT colonogra- nous adenomas is considerably higher. phy as a routine screening examination is still Adenoma surveillance reduces the risk of evolving. Still, only a minority of colorectal 227

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A B

Figure 5.20. Synchronous hepatic flexure adenocarcinoma (A, arrow) and ascending colon adenoma (B, arrowheads). C: Two synchronous adenocarcinomas in another patient, a circumferen- tial cancer in the ascending colon (arrow) and an infiltrating one in the transverse colon (arrowheads). C

cancers are detected by screening asymptomatic first-degree relative with a colon carcinoma or individuals. large adenoma and those with a prior adenoma Numerous studies have concluded that fecal or carcinoma. High risk includes those with occult blood testing is cost effective in detecting inflammatory bowel disease, familial polyposis, colorectal cancer. Although patient recruitment and nonpolyposis colorectal cancer syndromes. and test sensitivity vary considerably, its low Screening of inflammatory bowel disease cost makes it attractive. As one example, in a patients involves a different concept than for defined region in Spain a participation rate of other patients; cancer in these patients does not 56% was achieved and a majority of detected arise from adenomas, and screening consists of cancers were Dukes’ stage A (120); thus an random biopsies and a search for dysplasia. improvement in diagnostic stage is feasible, No consensus has developed in the gastro- with, one hopes, an improved survival. intestinal literature about surveillance screen- Patients are generally assigned to one of three ing time intervals. After an initial colonoscopic colon cancer risk categories: average, moderate, polypectomy, whether patients are assigned to and high. Moderate risk includes those with a follow-up surveillance either every two years or 228

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dations suggested depend on the initial assump- tions used. First degree relatives of colorectal cancer patients are at increased risk for adenomas and cancers. A French case-control colonoscopic screening study of first-degree relatives of col- orectal cancer patients (i.e., those of moderate risk) found an odds ratio of 1.5 for adenomas, including an odds ratio of 2.6 for high-risk ade- nomas (≥1cm in size or containing a villous component) (122); the prevalence of high-risk adenomas in relatives was higher when the index patient was younger than 65 years, was male, and had a distal rather than proximal cancer. The above discussion involves mostly conventional colonoscopy; a double-contrast barium enema was not considered as an alter- native. Barium enema sensitivity for detecting a carcinoma or larger adenoma is 85% to 95%. Several studies have concluded that a double- Figure 5.21. Metachronous colon carcinoma. A barium enema contrast barium enema is cost-effective for performed through a descending colostomy identifies a right colorectal cancer screening. Using published colon cancer (arrow).The patient had had a previous rectal car- estimates of cost and effectiveness of colorectal cinoma resected. cancer screening of a double-contrast barium

four years does not appear to affect over-all risk of developing a new adenoma. Even if a more protracted study leads to a slight increased risk of new neoplasms, this risk should be counter- balanced by the fewer examinations necessary and thus presumably decreased over-all colono- scopic complication rate. In general, in average- risk individuals the interval between screening examinations can be expanded beyond 5 years, provided the initial examination does not detect a neoplasm. Assuming a compliance of 60% with initial screening, a hypothetical study of 50-year-old white individuals at average risk for colorectal cancer found the most effective strategy to be annual fecal occult blood testing plus sigmoi- doscopy every 5 years starting at age 50 years, followed by colonoscopy if a polyp is detected (121); such a scenario achieved an 80% reduc- tion in colorectal cancer mortality compared with no screening. If, on the other hand, screen- Figure 5.22. A 15-mm sigmoid adenocarcinoma (arrow) ing compliance is assumed to be 100%,the study detected on a screening barium enema. Initial colonoscopy concluded that screening more often than every could not detect this tumor, probably because of extensive 10 years was prohibitively expensive. Similar to colon redundancy. The patient eventually underwent sigmoid other modeling studies, the optimal recommen- resection. 229

COLON AND RECTUM enema performed every 3 years (or every 5 the midgut portion of the colon as compared to years with annual fecal occult blood testing), the hindgut. In general, the presence of neu- an incremental cost-effectiveness ratio of roendocrine differentiation is associated with a <$55,600 per life-year saved was achieved, com- poor prognosis. pared to colonoscopic screening with a cost- Superficial spreading intramucosal tumors effectiveness ratio of >$100,000 per life-year (defined as epithelial tumors >30mm in dia- saved (123). meter), consist of both adenomas and carcino- Women with previous breast, endometrial, or mas and tend to be located in the cecum and ovarian cancer are at increased risk of develop- rectum; most superficial spreading carcinomas ing a colorectal cancer. Should women with have an adenomatous component and consist these cancers undergo preoperative barium of a low-grade carcinoma. Thus most super- enema or colonoscopic screening? Reccomen- ficial spreading tumors develop initially as an dations vary, because risk of colon adenomas adenoma. and carcinomas is low. A typical one is that in One uncommon histologic subtype is a signet otherwise asymptomatic women under 50 years ring cell carcinoma. These tumors tend to infil- of age no colon screening is necessary, but trate readily, and some even have a scirrhous in those over age 70 years such screening is or linitis plastica appearance. They occur in recommended. younger patients; patient survival is shorter A double-contrast barium enema is associ- than with more typical adenocarcinomas. ated with a perforation rate of about 1/25,000, A clear cell adenocarcinoma, similar to renal which is less than one tenth that of colonoscopy. clear cell adenocarcinomas, also develops on rare occasions in the colon. Pathology A rare colon adenocarcinoma <10mm in size infiltrates the submucosa or invades the submu- Normally proliferating cells are located in cosal lymphatics or blood vessels. These lesions colonic crypt bases, on the other hand, trans- typically have a polypoid appearance, although forming growth factor-b (TGF-b) immunoreac- an occasional one is flat. An rare early colonic tive and apoptotic cells are close to the surface, cancer will metastasize to the liver (124). corresponding to normal migration of colono- Proximal and distal colon cancers have dif- cytes. Distribution of proliferating and TGF-b ferent clinical presentations, differ in prognosis, immunoreactive cells is reversed in adenoma- and have different epidemiologic aspects. A tous polyps, suggesting that cell migration in study of DNA ploidy and overexpression of adenomas is not toward the lumen but inward. nuclear p53 found proximal tumors to be more Traditionally, development of colorectal often diploid than distal ones and distal tumors carcinomas was ascribed to an adenoma-to- to have more p53 overexpression than proximal carcinoma transformation sequence. This ones, suggesting a different carcinogenesis for concept was modified when it was realized that these tumors (125). Some investigators believe some small adenomas also have a malignant these cancers should be considered different potential, albeit small, and was modified further tumors. when flat carcinomas were detected developing Some colorectal adenocarcinomas are as- de novo from polyp-free mucosa. These flat sociated with considerable mucin production. (also called depressed) carcinomas appear to Different properties between mucinous and arise from a different precursor and suggest a nonmucinous colorectal carcinomas suggest different pathway for their carcinogenesis than different carcinogenic pathways. the adenoma-to-carcinoma cycle. Finally, mole- A colorectal carcinoma occasionally calcifies. cular biology enters the picture by showing a Most of these are mucinous adenocarcinomas. lack of K-ras mutations in carcinogenesis of flat Distinctly unusual, however, is heterotopic bone colonic carcinomas.A multipotential stem cell is formation. probably located within the mucosa. The pres- Although imaging and colonoscopy can ence of neuroendocrine or squamous differen- suggest that a particular lesion is a carcinoma, tiation in some colorectal carcinomas argues the final diagnosis is established by a patholo- that such differentiation evolves in several dir- gist from either a biopsy or a surgically resected ections; such differentiation is more common in bowel. Whether a pre-resection biopsy should 230

ADVANCED IMAGING OF THE ABDOMEN be obtained from a tumor showing obvious detected by colonoscopy were more likely to be malignant imaging characteristics is a matter of Dukes’ class A (25%) than cancers detected by opinion and established local practice. Most barium enema (10%). biopsies of primary colon carcinomas are A retrospective colon cancer study from a obtained via colonoscopy (or sigmoidoscopy for well-defined geographic region in Norway rectosigmoid lesions), although percutaneous found that a barium enema correctly detected a biopsy using imaging guidance is feasible for cancer in 91% of 386 tumors, a cancer or major larger tumors. precancerous lesion was overlooked in 7%, and the examination was not possible in 2% (127); Detection colonoscopy, on the other hand, correctly detected cancer in 80% of 215 tumors, cancer or Barium Enema: The relative roles of barium a major precancerous lesion was overlooked in enema, flexible sigmoidoscopy, and colo- 6%, and colonoscopy was technically incom- noscopy are not established. A number of plete in 14%. studies have shown a superiority of colonoscopy Endoscopy (Conventional Colonoscopy): In an over barium enema. The problem with most of Indiana study, colonoscopy performed by gas- these studies is that colonoscopy is used as a troenterologists was more sensitive (97%) for gold standard and the studies are performed by cancer detection than those done by nongas- gastroenterologists, but barium enemas were troenterologists (87%) (126). performed by general radiologists and the How accurate is colonoscopy in localizing a results are often biased against barium enema. colorectal cancer? One study of 77 cancers A barium enema, however, does detect most revealed significant errors in tumor localization pedunculated, sessile and infiltrating colon (Fig. in 8% (a significant error was defined as a 5.23) and rectal (Fig. 5.24) carcinomas. change from the preoperative planned resection In a retrospective multihospital Indiana to an alternative resection) (128). A retrospec- study, the sensitivity of colonoscopy for detect- tive study of colorectal cancers not detected by ing colorectal cancer (95%) was greater than colonoscopy performed within 3 years of diag- with a barium enema (83%) (126); the sensitiv- nosis suggested that 57% of the cancers were ity of a double-contrast barium enema (85%) “missed,” and 43% were believed not to have was no different from that of a single-contrast been reached, although some right colon study (82%). Barium enema performed no cancers recorded as missed may have been not better in the right than the left colon. Cancers reached (129); the authors suggested that cecal

A B

Figure 5.23. Colon adenocarcinoma. A: A double-contrast barium enema identifies a tight circumferential cancer.The entire colon could be studied in spite of the tight obstruction.B: This patient presented both with bleeding and obstruction.Barium enema reveals an ulcerated (arrows), circumferential sigmoid cancer. 231

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A B

Figure 5.24. A: Distal rectal carcinoma (arrows) presenting as a diffuse carpet-like infiltrate. (Courtesy of Arunas Gasparaitis, M.D., University of Chicago.) B: Polypoid, infiltrating rectal carcinoma (arrow).

intubation should be verified by specific land- performed the same day as conventional marks in all instances, and failure to reach the colonoscopy achieved a 58% sensitivity and cecum should be followed by a prompt barium 52% specificity in identifying polyps, with sen- enema or CT colonography. sitivity for polyps ≥1cm being 86% (135). Computed Tomography: Computed tomogra- After bowel preparation and colon air insuf- phy of some large, fungating ascending colon flation, 300 patients underwent CT scanning carcinomas infiltrating to pericolic fat identifies in supine and prone positions using 3-mm segmental distal colonic wall thickening. The collimation and single breath hold (136); histopathology of resected specimens reveals transverse CT images, sagittal and coronal ref- submucosal and subserosal edema, chronic ormations, and 3D endoluminal images com- inflammation and fibrosis, or both (130). pleted the CT colonography. Using conventional Not all focal colorectal tumors detected by CT colonoscopy results as a gold standard, this or MR are neoplastic. An adjacent abscess can study achieved a sensitivity of 90% for detect- readily mimic a necrotic cancer and vice versa ing polyps 10mm or larger, 80% for polyps (Fig. 5.25). Endometriosis is another example. 5.0 to 9.9mm, and 59% for polyps <5mm; of Intravenous contrast enhancement aids note is that CT colonography detected all carci- polyp detection (131); both benign and malig- nomas. Intravenous contrast provides colonic nant polyps enhance with contrast, while resid- wall and tumor enhancement. Enhancement ual content does not. Enhancement significantly significantly improved visualization of 6- to improves visualization of 6–9 mm polyps (75% 9-mm polyps (75% postcontrast versus 58% postcontrast versus 58% precontrast) (132). precontrast) (9). One potential pitfall for CT Contrast also aids detection of local tumor colonography is the occasional carpet-like (137) extension and any lymphadenopathy. Most or flat cancer. Most studies suggest that multi- published performance data on CT colonoscopy planar 3-D endoluminal images achieve better are summarized in a 2003 book on this topic sensitivity and specificity than 2-D images; nev- (133). ertheless, in any one patient a combination of Studies suggest that CT colonography is images is often necessary for full evaluation. competitive with conventional colonoscopy in Computed tomographic colonoscopy is an detecting both benign and malignant polyps alternative to barium enema and conventional >1cm. In patients with colonic tumors colonoscopy, especially in frail, elderly patients. (confirmed at endoscopy or surgery), axial and Detection of small polyps in these patients is multiplanar CT detected all malignancies (134); not as relevant as in younger patients. all missed benign tumors were <8mm in diam- Ultrasonography: Endorectal US detects eter. Computed tomographic colonoscopy rectal tumors. Attempts have been made to 232

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A B

C D

Figure 5.25. Pararectal abscess mimicking a rectal carcinoma.Constipation developed after prostatic resection 4 months previously for benign hyperplasia. A,B: Two pelvic CT images reveal a rectal tumor narrowing the lumen (arrows). C,D: T1– and T2–weighted images show rectal wall thickening and an adjacent fluid-filled structure (arrow),suggesting an abscess or necrotic tumor.(Courtesy of Egle Jonaitiene, M.D., Kaunas Medical University, Kaunas, Lithuania.)

detect a malignancy arising within a rectal depressed) colon adenomas and carcinomas do villous adenoma, but results have been disap- not have a predominant intraluminal growth pointing. In general, rectal villous adenomas pattern; rather, they show a tendency toward are resected regardless of imaging or biopsy early submucosal invasion and early metastasis. findings. Nevertheless, they grow slowly. A retrospective collection of nine flat colon carcinomas found Uncommon Type/Presentation an initial mean 12-mm diameter, and it took these cancers an average of 32 months to double Flat (Depressed) Adenomas and Carcinomas: So- in size; a comparable sample of polypoid carci- called flat (also called depressed and superficial nomas doubled in size, on average, in 9 months 233

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(138); with time, flat cancers continued with a resolution available with multidetector CT, nonpolypoid growth pattern. Cell kinetics and should be detectable with a high-quality molecular alterations in flat tubulovillous study. tumors suggest that they represent a distinct Linitis Plastica: The rare primary colorectal entity differing from their polypoid counterpart linitis plastica, or scirrhous carcinoma, usually (139). Some evidence suggests that flat colonic develops in a setting of inflammatory bowel tumors evolve from colonic mucosa overlying disease and in younger patients than more lymphoid nodules. typical colon cancers. Metastases are not These cancers are less common than those uncommon when such a primary tumor is first evolving via the adenoma-carcinoma sequence. identified. A higher proportion develop in a setting of Both colonoscopic and barium enema inflammatory bowel disease and radiation proc- findings can be subtle, with a typical appearance tocolitis. Some are rather aggressive and when resembling a benign stricture (Fig. 5.26). Com- still small have already metastasized to the liver, puted tomography reveals these scirrhous but these are rare exceptions. carcinomas as circumferential, homogeneously Comparing flat adenomas and adenocarcino- enhancing lesions. The involved colon wall is mas evaluated in Stockholm and Tokyo by the thickened considerably. The sensitivity in same pathologist, the Japanese lesions were detecting these lesions depends on tumor size more advanced with regard to dysplasia and and quality of CT study. Endoscopic US of rectal were more aggressive (140), suggesting the pres- linitis plastica shows a circumferential thicken- ence of different geographic manifestations. ing of the rectal wall, with thickening involving Complicating the picture, in the United States a mostly the submucosa and muscularis propria; number of small, flat umbilicated tumors are endoscopic US also detects perirectal fat hyperplastic polyps rather than neoplasms. infiltration. Although many radiologists believe that even In general, breast and stomach carcinomas a technically excellent double-contrast barium metastatic to the colon have a linitis plastica enema does not detect most flat colonic neo- appearance more often than a primary colon plasms, a Japanese study suggests otherwise scirrhous carcinoma. (141); among 97 early flat and depressed colorectal cancers, a double-contrast barium enema detected converging folds and semilunar deformity more often in cancers with moderate- to-massive submucosal extension than in those confined to mucosa or with only focal sub- mucosal extension. Also, deep depressions, an irregular surface in these depressions, and tumors >20mm were predictive of submucosal extension (141); using these radiographic findings, the authors achieved an overall accu- racy of 85% for identifying depth of invasion. Similar to a barium enema, small flat colon adenomas and adenocarcinomas may not be detected with conventional endoscopy because of their similar translucency to surrounding mucosa. They are identified as a slight mucosal deformity, a slightly more reddish color than surrounding mucosa, and by loss of the vascu- lar network pattern. Undoubtedly these small lesions were often previously overlooked. Potentially,CT colonography with IV contrast will detect flat neoplasms. These tend to be slightly hypervascular compared to normal Figure 5.26. Colon linitis plastica. (Courtesy of Arunas colonic mucosa and, especially with the higher Gasparaitis, M.D., University of Chicago.) 234

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Perforation: Previously performed water- soluble contrast enema has been replaced by CT. Computed tomography readily identifies these mostly advanced tumors, with a majority being associated with an abscess near the tumor. An occasional carcinoma perforates into adjacent soft tissues and leads to extraintestinal gas or subcutaneous emphysema (Fig. 5.27). At times unusual fistulas form. Technetium-99m- DTPA renography in a patient with hematuria revealed sigmoid colon radioactivity extending to the transverse colon (142); a sigmoid adeno- carcinoma had invaded the bladder and formed a colovesical fistula. Do patients with a perforating colon carci- noma have a worse prognosis than those Figure 5.28. Obstructing carcinoma (arrow). CT colonography without a perforation? Comparing perforating can also study the proximal colon. Sagittal images are helpful cancers and obstructing cancers undergoing in surgical planning. (Courtesy of W. Luboldt, M.D., Johann emergency surgery, no significant difference in Wolfgang Goethe University, Frankfurt-am-Main.) survival or disease progression was evident between these two groups (143). Obstruction: The size of colon cancers when first detected have decreased during the last several decades, yet it is still common in most colonic obstruction due to a large, bulky tumor. practices to see a patient first present with These patients first undergo proximal colon decompression and only later have definitive cancer resection.A sufficiently tight obstruction obviates both a complete barium enema and colonoscopy, studies not only defining an obstructing tumor but also detecting any synchronous neoplasm. In such a setting, preoperative CT colonography is very useful to evaluate the proximal colon. In 19 patients with distal occlusive colorectal carcinomas, pre- operative CT colonography identified all occlu- sive cancers and also detected synchronous lesions—two cancers and 20 other polyps (144), findings confirmed by other studies (145) (Fig. 5.28). Expandable intraluminal stents are useful in malignant colonic obstructions. A pretherapy stent placed through an obstruction provides decompression, allows a bowel-cleansing regimen to be employed, and thus obviates a preliminary colostomy (146). After decompres- sion, these patients undergo tumor staging, and a decision is made whether to proceed to cancer resection or whether successful stenting is to be the primary palliative therapy. The success Figure 5.27. Perforated right colon carcinoma (arrows) in a rate in stent placement varies but typically is patient suspected to have acute appendicitis. Soft tissue gas in about 90%; thus stent placement was successful the necrotic tumor mimics an appendiceal abscess. in 88% of 80 patients and bowel obstruction 235

COLON AND RECTUM resolved in 67% (146).A multicenter study of 71 Table 5.4. Tumor, node, metastasis (TNM) staging of colorectal patients with acute malignant obstruction tumors found self-expandable metallic stent placement Primary tumor: to be technically successful in 90%, but it was Tx Primary tumor cannot be assessed not possible to advance across the obstruction T0 No evidence of primary tumor in 3% and the prostheses was poorly positioned Tis Carcinoma in situ: Intraepithelial or invasion of in 7% (147). lamina Stent complications include perforation and Tl Tumor invades submucosa stent dislocation. Completely covered stents T2 Tumor invades muscularis propria T3 Tumor invades through muscularis propria into tended to migrate more than uncovered stents. , or into nonperitonealized Metastasis as the Initial Presentation: Only an pericolic or perirectal tissues occasional colorectal cancer presents first as a T4 Tumor directly invades other organs or metastasis, generally in the liver. A rare rectal structures, and/or perforates visceral cancer spreads via systemic veins, but pul- monary metastases also occur occasionally Lymph nodes: from a nonrectal site. Nx Regional lymph nodes cannot be assessed Bone and cerebral metastases as an initial N0 No regional lymph node metastasis presentation are rare. A cecal carcinoma in a Nl Metastasis in 1 to 3 regional lymph nodes cirrhotic patient first presented with umbilical N2 Metastasis in 4 or more regional lymph nodes metastasis (Sister Mary Joseph node) (148). A Distant metastasis: curiosity is a single microscopic metastatic Mx Distant metastasis cannot be assessed focus in a resected thyroid colloid nodule in a M0 No distant metastasis patient with unsuspected sigmoid colon carci- M1 Distant metastasis noma and multiple liver metastases (149). Tumor staging: AJCC/UICC DUKES-3* Staging Stage 0 Tis N0 M0 — Stage I T1 N0 M0 A General: Several staging systems are in use, T2 N0 M0 A including the tumor, node, metastasis (TNM) Stage IIA T3 N0 M0 B system (Table 5.4). The Dukes staging system Stage IIB T4 N0 M0 B was originally designed for rectal carcinomas, Stage IIIA T1,2 N1 M0 C but over the years it has been expanded to Stage IIIB T3,4 N1 M0 C include colon cancers; a number of Stage IIIC any T N2 M0 C modifications and subdivisions have evolved, Stage IV any T any N M1 D and if the Dukes system is used, the specific AJCC, American Joint Committee on Cancer; UICC, Union Interna- modification employed should be identified. tionale Centre le Cancer. A small colorectal cancer initially tends to *Dukes B is a composite of better (T3, N0, M0) and worse (T4, N0, grow more circumferentially rather than longi- M0) prognostic groups, as is Dukes C (any T, Nl, M0 and any T, N2, M0). tudinally along the colon wall. Spread occurs via Source: From the AJCC Cancer Staging Manual, 6th edition (2002), both the lymphatics and hematogenously. A published by Springer-Verlag,New York,NY,used with permission of cancer in the intraperitoneal colonic segments the American Joint Committee on Cancer (AJCC), Chicago, IL. is prone to form peritoneal carcinomatosis once the serosal barrier is breached. Some carcinomas, especially well- differentiated ones, invade extensively into sur- Ability to detect perirectal node involvement rounding organs without evident metastasis to varies with node size. In general, malignant lymph nodes or more distant structures. For nodes are larger than nonmalignant ones, example, a large transverse colon carcinoma in although some normal sized nodes are invaded a 60-year-old woman had invaded the adjacent and some enlarged ones are not. Enlarged duodenum and pancreas and was in close lymph nodes can be due to reactive inflamma- contact to the superior mesenteric vein (150); tion. In addition, metastatic nodes range from no metastases were evident and en bloc resec- being partially to totally invaded. Similar to tion revealed no lymph node spread. metastatic nodes at other body sites, aside from 236

ADVANCED IMAGING OF THE ABDOMEN node size, node metastases do not correlate with A meta-analysis of articles published up to a specific imaging appearance. Also, some col- 2002 found that for muscularis propria invasion orectal cancers metastasize to more distant by a rectal cancer US and MR had similar sen- lymph nodes and bypass closer nodes. Such sitivities but US specificity was 86% and MR skipping nodal metastases are detected in about 69% (153); sensitivity for perirectal tissue 10% of patients; patients with skipping nodal invasion was: CT 79%, US 90% and MR 82%, metastases have a significantly better prognosis with similar specificities. All three modalities than those without bypassed metastases. were comparable for detecting lymph node Routine preoperative CT and MR colon involvement. cancer staging is of limited use because of low Multidetector CT is more accurate in staging accuracy in assessing the depth of tumor inva- more advanced rectal cancers than more sion and detecting early lymph node invasion, superficial ones; CT does not provide rectal wall but these examinations are very useful for details. Adding multiplanar reconstruction detecting invasion of adjacent structures and improves local staging of these cancers. metastasis to distant sites. Almost all colon In 53 consecutive patients with distal rectal cancers are resected. Patients with rectal cancer, carcinoma, CT sensitivity for detecting perirec- on the other hand, have additional therapeutic tal and inferior mesenteric lymph node metas- options, and initial staging often determines the tases was 53% and specificity 85% (154). type of therapy employed. Computed tomography using a water enema The Radiology Diagnostic Oncology Group (hydro-CT) appears useful in staging rectal concluded in 1996 that CT and MRI accuracies cancers. Hydro-CT studies tend to be more were equivalent in depicting transmural tumor accurate than no enema studies; increased accu- spread, assessing lymph node involvement, racy is mostly in detecting invasion within or and detecting liver metastases (151). Due to beyond the muscular layers. A CT study of advances in CT and MR equipment and soft- patients with rectal cancer using a tap water ware design since then, however, these results enema, IV contrast, and pharmacologic bowel should be viewed as obsolete. hypotonia reached a sensitivity of 90% and Staging is best approached by treating rectal specificity of 70% in differentiating tumors and nonrectal cancers separately. limited to bowel wall from those invading Rectal Carcinoma: Rectal wall penetration extrinsically (155). and pelvic lymph node involvement are the Conventional US has been largely supplanted major prognostic factors in predicting recur- by endorectal US in staging rectal carcinomas. rence. Some lymph nodes <5mm in diameter Endorectal US is very accurate in T-staging already contain metastases, a limitation in the superficial cancers but not more advanced imaging prediction of tumor spread. Neverthe- cancers because of limited acoustic range. less, the sensitivity for detecting positive lymph Some authors express endorectal US staging nodes is greater for rectal tumors than for using TNM nomenclature—called the uTNM more proximal colonic tumors because benign classification. Although some results are prom- perirectal adenopathy is uncommon. ising, the overall conclusions are rather pes- The prevalence of lymph node involvement simistic, especially for detecting lymph node with rectal cancers is related to tumor depth. metastasis. Among rectal cancers, lymph node involvement Endoscopic resection should be possible if was as follows: T1,6%; T2,20%; T3,66%; and T4, imaging could differentiate between mucosal 79% (152). A biopsy finding of lymphatic vessel and submucosal invasion. A number of stuties invasion was highly indicative of lymph node of early rectal cancer concluded that endoscopic metastasis. US is not accurate enough to determine appro- One pathway for the spread of sigmoid and priate therapy for these tumors. On the other high rectal cancers is via the inferior mesenteric hand, a more recent study found that endorec- lymph chain, but specific spread is unpre- tal US achieved a sensitivity and specificity of dictable and can include the inferior mesenteric 93% and 71%, respectively, and MRI 100% and lymph nodes, nodes adjacent to rectum, and 60% for detecting rectal wall penetration (156). nodes at the root of the inferior mesenteric Endorectal US does not reliably detect muscu- artery. laris propria invasion (T2 tumors). Endorectal 237

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US does, detect perirectal fat invasion (T3 detection decreases after preoperative radio- tumors). Tumor spread to more distal struc- therapy or chemoradiotherapy. tures, such as bladder, is more problematic. In patients with known rectal tumors, Ultrasonography of the distal rectum is more endorectal US and MRI achieve comparable difficult and the tissue planes are less well staging results. The advantages of endorectal US defined than more proximally, and endoscopic are its small-diameter instruments, its ready US staging accuracy in the distal rectum is lower availability, it is technically less demanding, and than in the middle or proximal segments. On it costs less; MRI, on the other hand, is operator the other hand, endorectal US is accurate in independent and also evaluates other sites. evaluating anal canal infiltration by low rectal Magnetic resonance imaging using an cancers. The overall tendency in staging rectal endorectal coil provides more detail than villous tumors with endoscopic US is to over- similar MRI using a surface coil. On the other stage rather than understage. Endoscopic US in hand, use of an endorectal coil combined with patients with a rectal adenocarcinoma per- imaging using external coils appears advanta- formed within 2 weeks prior to surgery and geous in assessing both intramural tumor radiation therapy overstaged 21% and under- infiltration and more distal pelvic spread. Little staged 9% of patients (157). Overstaging of the data exists on placing such combined imaging depth of invasion is due, in part, to tumors in a proper perspective. located close to an uninvolved layer, not High-spatial resolution MRI using T2- uncommon adjacent inflammation and hyper- weighted FSE images identifies mesorectal vascularity, which tend toward a more ane- fascia, peritoneal reflection, Denonvilliers fascia choic appearance than tumor infiltration. and adjacent structures. Magnetic resonance Microscopic invasion accounts for some imaging has a tendency to understage rectal understaging. carcinomas (Fig. 5.29). Overstaging in some After a rectal polypectomy with an adenocar- patients is due primarily to the presence of adja- cinoma discovered in the specimen, endorectal cent perirectal inflammation. US detected residual tumor with a sensitivity of Rectal distension by a water enema improves 100% but a specificity of only 44% (158). MR detection of rectal wall penetration. Using a How accurate is endorectal US in detecting rectal ferric ammonium citrate enema, spin local lymph node invasion? Considerably more echo MRI identifies most rectosigmoid cancers. lymph nodes are involved at histologic exami- Preoperative MR staging of rectal cancer nation than are detected by US, and a number achieved a 100% sensitivity and 70% specificity of studies have concluded that endoscopic US is in distinguishing tumor stages worse than too unreliable to be used in preoperative patient Dukes’ stage A (159); on T1-weighted images a selection. Some enlarged lymph nodes are due rectal superparamagnetic contrast enema to reactive inflammation and not tumor infi- creates a signal void in a distended lumen while ltration. The ability to detect perirectal nodes wall contrast enhancement by IV gadolinium varies with node size. In general, malignant differentiates mucosa, muscle layers, and nodes are larger than nonmalignant ones, perirectal space, details not obtainable with although overlap exists. Metastatic nodes range nonenhanced images. from being partially to totally invaded. Similar In a randomized phase II trial, preoperative to metastatic nodes at other body sites, aside MR using the superparamagnetic iron oxide from node size, node metastases do not corre- rectal contrast agent ferristene and IV contrast late with a specific imaging appearance. Several achieved a sensitivity of 97% and specificity of studies concluded that endoluminal US does not 50% in staging carcinomas higher than T2 stage reliably identify the extent of lymph node (160); using receiver operator characteristic involvement. The role of 3D endorectal US (ROC) analysis, MR differentiated between in staging rectal carcinoma remains to be T1/T2 and T3/T4 tumor stages with a ROC established. index of 0.85. Higher viscosity rectal contrast Whether patients are treated by radiotherapy agent formulations were superior to low- or chemotherapy prior to surgery also appears viscosity formulations, but no significant differ- to influence rectal US accuracy. Diagnostic US ences were found between high and low iron accuracy for wall infiltration and lymph node content agents. 238

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A B

Figure 5.29. Rectal carcinoma.Precontrast (A) and contrast-enhanced (B) coronal T1–weighted MR images identify a left distal rectal tumor (arrows) invading perirectal fat. (From Burgener FA, Meyers SP,Tan RK, Zaunbauer W. Differential Diagnosis in Magnetic Reso- nance Imaging. Stuttgart: Thieme, 2002, with permission.)

Similar to other imaging modalities, small Nonrectal Carcinoma lymph node metastases are not identified, although iv SPIO agents show promise. Non- Although some earlier studies claimed high CT malignant nodes are hypointense or have a sensitivity and specificity in detecting local hypointense center, while eccentric and hyper- tumor extension (T stage), more recent studies intense nodes tend to contain metastases larger are more pessimistic. Local CT staging accuracy than 1 mm in diameter, although overlap does increases at higher disease stages. In general, exist (161). the presence of obvious pericolic spread and Can MRI predict sphincter salvage in these nodal involvement is more reliable than nega- patients? A prospective MRI study of patients tive findings. Nodal involvement is assessed by with a low or middle third rectal adenocarci- simply detecting enlarged nodes. Disappoint- noma (defined as <12cm from pectinate line) ingly, an accuracy of only about 50% has been using rectal and IV contrast and a flexible achieved by a number of studies for nodal surface coil achieved 100% sensitivity and 98% metastases. specificity in assessing anal sphincter infiltra- Most current CT colonography research tion and 90% sensitivity and 100% specificity in involves tumor detection, although some evi- detecting adjacent organ infiltration (i.e., T4 dence suggests that it also should have a role in stage) (162); nodal staging, however, was sub- staging. Thus one study achieved an overall optimal—MRI reached a 68% sensitivity and accuracy of 83% in T staging and 80% in N 24% specificity. staging when employing contrast enhanced Magnetic resonance imaging potentially dif- transverse and multiplanar reformated CT ferentiates between mucinous and nonmuci- colonography, with images obtained in the arte- nous rectal tumors. On T2-weighted fast rial phase focusing on the suspected neoplasm SE images mucinous tumors had signifi- and portal venous phase images on the entire cantly higher tumor-to-muscle, tumor-to- abdomen and pelvis (164). fat, and tumor-to-urine signal intensity ratios The results of hydrocolonic US to detect and compared with nonmucinous tumors (163); stage colorectal carcinomas have been disap- most mucinous tumors also revealed peripheral pointing. Assessment of lymph node involve- post–gadolinium contrast enhancement. ment is poor. 239

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Comparing different MR studies is difficult that also involve the submucosa and thus has an because results vary considerably depending imprecise meaning. on sequences employed. A number of studies Spread beyond muscularis mucosa signifies have concluded that MR staging accuracy, an invasive cancer and wider excision is indi- including nodal involvement, is similar to that cated, although some pedunculated polyps are obtained with CT. Nevertheless, MRI staging is resected endoscopically if no vascular or stalk still in its infancy and future improvements hold invasion is evident (Fig. 5.30). promise. One interesting fusion of procedures con- 18F-fluoro-deoxy-D-glucose PET appears sists of laparoscopically assisted endoscopic useful in staging colon cancer. It identifies polypectomy for broad-base polyps. Under primary carcinomas (including in-situ carcino- general anesthesia, endoscopic polypectomy is mas) but is insensitive in detecting lymph node assisted by laparoscopy and the polyp site is metastases (165); similar results were obtained then sutured using a laparoscopic approach. with CT. On the other hand, 18F-FDG-PET Surgical: Colorectal cancer surgery is per- detects extrahepatic colon metastases missed by formed in the very old, with cancer-free survival other imaging modalities (including CT and in these elderly patients being quite good. Indi- MRI); PET detects extraperitoneal nodal metas- cations for surgery should be rather liberal; this tases, pulmonary metastases, and regional is in contradistinction to gastric cancer surgery lymph node involvement. Thus PET influences where survival is much more limited. patient selection for hepatic resection. In addition to preoperative imaging, liver But 18F-FDG-PET is false-positive in patients palpation at laparotomy aids in detecting liver with inflammatory bowel or other sites of metastases at the time of surgery. Intraoperative inflammation. liver US is also very useful in further staging and Radioimmunoscintigraphy holds promise in patient selection for additional therapy but detecting metastases, but sufficient clinical data currently is not widely practiced. The quality of are not available on its use in initial staging. operative US influences considerably the results Operative gamma probe immunoscintigraphy obtained. achieves high sensitivity in detecting liver and Preliminary results of laparoscopic colon extrahepatic abdominal tumor sites but is little cancer resection are encouraging, with patient practiced. survival, tumor recurrence, and mortality being similar to those of open resection. The liver cannot be palpated during laparoscopic colo- Therapy Rather active current research interests involve immunotherapy and genetic therapy. A current trend is toward more aggressive therapy of metastases with such modalities as hyperther- mia, cryoablation, and various combination of systemic therapy and surgery. Currently a majority of patients undergo colon cancer resection even in the face of metastases.

For Cure Endoscopic: A cancer that has not penetrated through the muscularis mucosa is considered a carcinoma-in-situ, and generally endoscopic polypectomy suffices. Terms synonymous with carcinoma-in-situ include intramucosal carci- noma, carcinoma limited to mucosa or lamina Figure 5.30. Pedunculated sigmoid adenocarcinoma (arrow). propria,and superficial carcinoma. The latter The stalk is seen as a circle within this 1-cm round, smooth term, however, is sometimes applied to cancers tumor. 240

ADVANCED IMAGING OF THE ABDOMEN rectal cancer resection, and this useful diag- radiotherapy provides tumor perfusion data nostic procedure, performed during an open from which a tumor perfusion index (PI) was resection, is thus lost. One proposal is that intra- established (167); the PI increased significantly operative laparoscopic US be included as part during the first 2 weeks of therapy, and then of laparoscopic colorectal cancer resection; it is decreased. A high initial PI value correlated possible to scan all liver segments through a with subsequent greater lymph node down- single port site for possible metastases. Never- staging and thus is potentially of prognostic theless, this is a complex procedure requiring significance. that a radiologist be present in the surgical suite; Radioimmunotherapy: The use of mono- all parenchymal segments and major intra- clonal antibody radioimmunotherapy for hepatic vascular and biliary structures need primary colorectal cancer is still in investi- to be identified during the scan. This takes gational status. Simultaneous injection of considerable time and effort. copper 67 and sodium iodide 125–anti-CEA European clinical trials of rectal cancer monoclonal antibody in six patients yielded an patients suggest that best results are achieved average Cu-67/I-125 ratio of 1.9 for tumor with radiation therapy followed by surgery. In uptake, 0.7 for blood, and 2.6 for tumor to blood the United States postoperative radio- and (168); one problem identified by the study was chemotherapy are used for T3 and N1 cancers. that Cu 67–monoclonal antibody tumor uptake One complication after radical surgery for rectal was too low while liver and bowel uptake was carcinoma is vesicourethral dysfunction. considerable. Radiochemotherapy: Local excision or Other: Ten patients with advanced pelvic endorectal radiotherapy are alternate therapies cancer (recurrent rectal and ovarian cancer) for local control of some select early rectal underwent sequential arterial cisplatinum and cancers. A number of studies have established mitomycin infusion via an extracorporeal that radiation therapy pre- and postsurgery circuit established by isolating pelvic vessels improves survival. Preoperative radiotherapy with balloon catheters placed above the aortic appears superior for local tumor control. and caval bifurcations and pneumatic cuffs at Radiochemotherapy alone is appropriate in a the thighs (169); although the authors estab- setting of an unresectable tumor. lished the feasibility for such extracorporeal Antitumor activity of some chemotherapeu- perfusion, 2-year patient follow-up failed to tic agents consists of thymidylate synthetase show a positive response. inhibition, an enzyme necessary in DNA syn- thesis (166); dose-limiting toxicities prevent Palliation their more widespread use. Nevertheless, adju- vant therapy with 5-fluorouracil and levamisole In the absence of metastases, a preoperative does increase the cure rate of stage III (Dukes’ definition of an unresectable cancer is often C) colon cancer patients. Likewise, radiation imprecise. Especially for rectal cancers, unre- therapy combined with chemotherapy appears sectability is often established only at surgery. to have a role in patients with stages II (Dukes’ Patients with unresectable rectal cancer B2) and III rectal cancer. undergo palliation therapy. A combination of A combination of adjuvant radiochemother- local excision, radiation, and chemotherapy is apy and radical surgery in patients with rectal balanced depending on the size of the local carcinoma achieves mixed results. Complete tumor spread, the size of the metastases, and life response to preoperative chemotherapy and expectancy. Repeat local excision is appropriate radiation therapy for locally advanced rectal for some. Even pelvic reradiation appears to cancer is achieved in a minority. In some have a role in select patients. Published reports patients such therapy also decreases cancer of brachytherapy have been disappointing. stage, thus permitting a sphincter-saving Endoscopic laser therapy using an Nd:YAG procedure. noncontact laser performed in patients with Computed tomography has a major role in obstructing or bleeding inoperable colorectal planning preoperative radiotherapy. cancers initially control symptoms in most Serial postcontrast infusion MRI in patients patients, but symptoms can be expected to with T3 rectal carcinoma during preoperative recur. 241

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For Obstruction: Most stents are inserted is a feasible alternative to both conventional retrograde for palliation of rectosigmoid colonoscopy and liver US in following these tumors.An occasional one is inserted antegrade patients (171). via a percutaneous cecostomy. In addition to Both CT and MRI have a major role in detect- relief of obstruction prior to surgery, expand- ing recurrence of colorectal cancers, with some able intraluminal stents decompress the bowel studies claiming an accuracy over 90%. A basic for palliation of a nonresectable tumor, obviat- question, however, is whether such early recur- ing a permanent colostomy (146). A multicenter rence detection influences survival. Current study of successful palliative stent placement data suggest a rather pessimistic answer. found bowel obstruction resolving within A prospectively, randomized study with pa- 24 hours of stenting in 96% of patients, with tients undergoing either intensive (yearly none requiring a colostomy for decompression colonoscopy, liver CT,chest radiography, clinical (170). review, and simple screening) or standard Complications, consisting of mild rectal follow-up (structured clinical review and simple bleeding, abdominal pain, stent malpositioning, screening tests only) found no significant dif- obstruction due to , and even- ference in survival between the two groups after tual tumor ingrowth into the stent lumen, are a 5-year follow-up (172); yearly colonoscopy not uncommon. Stents have perforated and failed to detect any asymptomatic local recur- migrated. rence, and only one asymptomatic curable Among survivors, estimated primary stent metachronous colon tumor was found. Liver CT patency rate was 91% at 6 months (146). resulted in earlier detection of hepatic metas- For Bleeding: An occasional patient with tases but did not increase the number of cura- colorectal cancer presents with massive and tive hepatectomies. potentially life-threatening bleeding. Even in a Local peritoneal involvement appears to setting of an unresectable tumor, transcatheter supersede other parameters in estimating embolization should be encouraged. Reembo- patient prognosis. Nevertheless, the clinical lization is performed if bleeding recurs. Most of significance of malignant cells in the peritoneal these patients eventually die from tumor cavity is not clear. For instance, in patients with cachexia rather than exsanguinate. no evidence of peritoneal metastases, peritoneal washing before elective colon resection for ade- Recurrence and Follow-Up nocarcinoma detected malignant cells in 32% of patients with tumor extending to the serosa General: Although screening for recurrence is (173); the 5-year survival rates were 48% for commonly practiced, guidelines on specific those with positive washing and 68% for those follow-up have not been established. Screening with negative washing, although multivariate practices for hepatic and pulmonary metastases analysis revealed no significant association vary considerably between hospitals. between positive washing and survival. Currently a CEA determination is the most Rectal Carcinoma: Recurrence of rectal carci- common test used to detect cancer recurrence. nomas is discussed separately because its Carcinoembryonic antigen has a high specificity recurrence patterns and imaging approach are for tumor recurrence and not uncommonly is distinct from those in more proximal colon. positive before imaging. On the other hand, Tumor recurrence must be distinguished from whether frequent CEA determinations prolong postresection fibrosis and surgical deformity survival is not clear. (Fig. 5.31). Staging of patients with a proven The role of colonoscopy in screening for rectal cancer after radiation and chemotherapy local recurrence is rather limited because only is especially difficult. Both CT and endorectal about 10% of recurrences are intraluminal. US overstage these cancers even in patients Colonoscopy does have a long-term role, subsequently found to have no residual cancer. however, in detecting new adenomas and No current imaging modality can reliably dis- metachronous cancers. Although colonoscopy tinguish between radiation fibrosis and residual does have a long-term role in detecting new ade- cancer, although MR and scintigraphy show nomas and metachronous cancers, preliminary promise (see below). With most imaging a studies suggest, however, that CT colonography baseline study 2 to 4 months after surgery is 242

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modality to evaluate for recurrence. Recurrence detection rates of >90% by endorectal US are being achieved, and this study appears espe- cially useful in this setting. CT achieves about an 80% sensitivity and specificity in detecting recurrence, while MRI sensitivity is similar but specificity is greater. A typical protocol for these patients consists of CT performed within 2 to 4 months after resection and repeated every 6 to 8 months during the first 2 years (with CEA testing); MRI is reserved for those with a positive or questionable CT finding, those with different clinical symptoms, and those with an increasing CEA. A biopsy is indicated if MRI does not resolve the issue. Postcontrast CT of active granulation tissue Figure 5.31. A double-contrast barium enema reveals a benign reveals considerable enhancement. Compound- anastomotic stricture (arrow) after sigmoid resection for cancer. ing the issue is that local recurrence of rectal cancer results in transient early enhancement at the anastomotic site; whether recurrence can be confidently differentiated from postoperative granulation tissue is not clear. very useful. Postoperative fibrosis retracts over After rectal cancer resection, the most time and gradually develops well-defined common CT finding of recurrence is a round or margins. nodular enhancing tumor.A retrospective study Recurrence after an abdominoperineal resec- of postsurgery or radiotherapy rectal cancer tion is most often local. It tends to infiltrate dif- patients who had at least three CT examinations fusely and is asymmetrical in appearance (Fig. concluded that relapse should be considered if 5.32). No consensus exists on the best imaging a presacral mass enlarges, appears inhomoge-

B

Figure 5.32. A: Recurrent rectal carcinoma (arrow) in a patient with a prior rectal cancer resection and a side-to-end low colorectal anastomosis. B: Tumor recurrence at anastomosis in another patient. Barium enema reveals an irregular, ulcerated A infiltrating tumor (arrows). 243

COLON AND RECTUM neous, and is asymmetric in outline, or if extrinsic component, CT and MRI are well enlarged lymph nodes develop and infiltrate suited for postresection follow-up. A baseline surrounding structures (174); an unchanged study aids the future differentiation of fibrosis appearance in several follow-up CT examina- from recurrent tumor. tions is evidence for lack of recurrence. A Superficially, a suture granuloma developing necrotic recurrence is often difficult to distin- after bowel resection and reanastomosis mimics guish from an inflammatory mass or abscess. local recurrence with both colonoscopy and a Some evidence suggests that radiation barium enema. fibrosis has a somewhat different MR enhance- Considering enhancement within 90 seconds ment pattern than postoperative scar tissue. of an abnormal structure on dynamic contrast- Granulation tissue developing shortly after enhanced subtraction MRI to signify a malig- rectal cancer resection shows marked post- nancy, MR achieved a 97% sensitivity and 81% contrast CT enhancement and is hyperintense specificity in differentiating fibrosis from recur- on T2-weighted MR images. Eventual fibrosis, rence during follow-up (176); using a finding especially evident after radiation therapy, of high signal intensity on T2-weighted SE is hypointense on both T1- and T2-weighted images as a criterion for malignancy, sensi- images. Fibrosis shows poor but variable tivity and specificity were only 77% and 56%, enhancement postcontrast. Retraction of sur- respectively. rounding tissues is common. Fibrosis exhibits Distal Recurrence: For unknown reasons, an irregular enhancement even years after colorectal cancer metastasis to a fatty liver is radiation therapy. uncommon. Technetium-99m–labeled anti-CEA antigen- Colorectal cancer metastasis to bone is not antibody scintigraphy appears to have a role in uncommon. At times bone biopsy is required detecting pelvic recurrence, with sensitivity both for diagnosis and to exclude osteomyelitis. being similar to that of CT. Sensitivity is greater Bone metastasis is more common with rectal with an increase in size of a recurrence. In select and cecal cancers than with other colon cancers. patients antibody scanning aids in differentiat- What is uncommon is to find a solitary bone ing recurrent tumor from fibrosis. metastasis or a metastasis years later. Signet 18F-fluoro-deoxy-D-glucose PET shows in- ring cell cancers appear to have a higher creased tumor uptake at recurrence sites; scar propensity for bone metastasis. Brain metasta- tissue has low FDG accumulation. FDG-PET in sis is uncommon but does occur. A rare metas- one study achieved a sensitivity of 82% and a tasis occurs within a laparotomy scar. specificity of 65%, but combined PET/CT sensi- In women with a prior colorectal adenocarci- tivity increased to 98% and specificity 96% in noma who then developed a new pelvic tumor, differentiating malignant from benign disease ovarian metastasis was found in 57%, a benign (175). ovarian neoplasm in 26%, and a primary With suspected local recurrence, either ovarian cancer in 17% (177); among women transrectal-guided fine-needle aspiration cytol- with a past colorectal cancer, a newly diagnosed ogy using a 21-gauge needle or a core biopsy uterine cancer was a primary endometrial with an 18-gauge needle appears appropriate. If adenocarcinoma in 73% and metastatic colon a tumor is palpable, digitally guided puncture is cancer in 20%. The rare colorectal carcinoma in feasible; for others, either CT or US guidance is adolescent girls frequently metastasizes to the used. Whether 3D endorectal US guidance aids ovaries; these ovarian metastases range from the biopsy of suspected perirectal recurrence solid, combined solid and cystic, to multilocular remains to be established. cysts, although they tend to be cystic less often Nonrectal Carcinoma: As a rough estimate, than in older patients. approximately 50% of patients undergoing Calcifications in metastatic colon carcinoma curative resection for Dukes C colorectal cancer are not uncommon; such calcifications are develop a recurrence within 3 to 5 years, and readily identified with CT. Ossification in a over 90% of them die from their cancer. In those metastatic colon carcinoma is rare. developing a recurrence, almost all colorectal Imaging studies useful in evaluating liver and cancers recur within 3 years. Because many extrahepatic metastases include conventional recurrent carcinomas consist primarily of an chest radiographs, CT, MRI, and scintigraphy. 244

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Resection of liver metastases is precluded in the PET appears to be more sensitive than CEA in face of extrahepatic metastases (liver metastases detecting tumor recurrence. In previously are discussed in more detail in Chapter 7). treated colorectal cancer patients with sus- Both 18F-FDG-PET and radioimmuno- pected recurrence, FDG-PET detects >90% of scintigraphy detect earlier local recurrence than liver and extrahepatic metastases, considerably is possible with CT or MRI and aid in identify- more than CT. In fact, currently FDG-PET is the ing tumor involving normal size lymph nodes. most accurate noninvasive modality for staging Their current use, however, is still rather limited patients with recurrent metastatic colorectal and their role in the latter clinical setting is not cancer. yet adequately established. Theoretically, colon cancer detection is Anaplastic Carcinoma improved by combining a monoclonal antibody, which has selective tumor affinity, with PET Colorectal small cell anaplastic carcinomas are scanning, which has increased sensitivity and rare. Some contain exocrine differentiation. resolution over conventional imaging. To test These tumors tend to be aggressive and metas- this hypothesis, an anticolorectal cancer mono- tasize early,both to lymph nodes and hematoge- clonal antibody (MaB 1A3) was labeled with nously. Staging should include CT of the chest copper 64, which is a positron emitting radionu- and abdomen and bone scintigraphy. cleotide (178); such monoclonal antibody-PET scanning achieved a sensitivity of 71% in detect- Adenosquamous/Squamous Cell Carcinoma ing confirmed tumor sites. In patients with suspected recurrent colorec- These are rare but aggressive colorectal tumors tal or ovarian carcinoma and normal or equiv- having a predilection for the rectum; some are ocal CT or MR studies, indium 111 satumomab associated with ulcerative colitis or with other pendetide (OncoScint) imaging and FDG-PET carcinomas. imaging are similar in their tumor detection About 70% of anal carcinomas are squamous abilities; the radioimmunoconjugate OncoScint and 30% are cloacogenic (179). Imaging has no is better at detecting carcinomatosis, but PET role in detecting these cancers but aids better detects liver metastases. Indium 111 sat- in staging. They spread mostly locally to the umomab liver imaging is suboptimal due to perirectal, inguinal, and iliac nodes; distal high background levels; nevertheless, it does spread is to the lungs and liver. provide relevant information about extent and Traditional therapy of anal carcinoma was location of recurrent colorectal cancer through- an abdominoperineal resection, which is rarely out most of the abdomen. It appears especially performed now, having been supplanted by useful in patients with normal other imaging radiation and chemotherapy. studies but a rising or high CEA level. An occa- sional indium 111 satumomab study is false Lymphoma positive, with activity detected in another tumor, such as a nonfunctioning adrenal Lymphomas range from diffuse gastrointestinal adenoma. tract involvement to, less often, being limited to Single photon emission computed tomogra- the colon. Cecum and rectum are the most phy (SPECT) immunoscintigraphy using Tc- common large bowel sites. Primary colon lym- 99m–anti-CEA monoclonal antibodies shows phomas tend to present as large intramural promise in follow-up after surgery. There are, infiltrating tumors. Over half of primary colonic however, problems in interpreting images non-Hodgkin lymphomas are diffuse large-cell because of variations in antibody distribution. lymphomas. It detects local or abdominal recurrence and Clinically, some colonic lymphomas present appears to be more accurate than CT in the with signs and symptoms similar to those of abdomen. an adenocarcinomas; others mimic inflamma- Scant literature exists on the usefulness of tory bowel disease. Less common presentations PET imaging in detecting recurrent colorectal are acute abdomen, intussusception, or simply cancer,although PET is more sensitive in detect- with an abdominal tumor. A possibility of lym- ing early recurrence than CT or MRI. In fact, phoma being misdiagnosed as inflammatory 245

COLON AND RECTUM bowel disease from superficial mucosal biopsies Liposarcoma has already been mentioned (see Ulcerative Colitis).Some of these patients undergo steroids Magnetic resonance imaging of liposarcomas therapy until a correct diagnosis of lymphoma reveal several patterns. Well-differentiated is made. In fact, lymphoma should be consid- liposarcomas have MRI characteristics similar ered in the differential diagnosis of a dense lym- to those of a lipoma, consisting of a well- phocytic infiltrate obtained from a segment of marginated tumor hyperintense on T1- bowel simulating either ulcerative colitis or weighted images, hypointense on T2-weighted Crohn’s disease. images,and showing little if any contrast enhan- Although not common, patients with cement; less well-differentiated liposarcomas leukemia have developed colon lymphoma. tend toward a heterogeneous appearance, with Overall, colonic lymphomas appear similar many containing varying amounts of necrosis. to those seen in the small bowel. A common In general, tumor necrosis varies inversely with appearance is that of an intramural infiltrating, the degree of tumor differentiation. sharply marginated tumor. Involved colon tends to be thickened and distorted, an aid in differ- Angiosarcoma entiating lymphomas from adenocarcinomas. Colonic angiosarcomas are rare. A cecal A lymphomatous large, ulcerated mass is less angiosarcoma occasionally intussuscepts. common. A rare appearance is aneurysmal dila- tion of the affected colonic segment. Unlike cecal adenocarcinomas, extension Histiocytoma across the ileocecal valve is common with lym- Primary colonic malignant fibrous histiocy- phomas, and the site of origin is often difficult tomas are rare. Initially these sarcomas are to determine; some authors use the term ileoce- confined to the colon wall, but with growth cal lymphoma to describe these tumors. Their ulcerate through the mucosa and bleed, or they differential diagnosis includes a mesenchymal invade the adjacent soft tissues. Peritoneal tumor and localized Crohn’s disease. implants and lymph node metastases are Double-contrast barium enema findings in evident with some. Also, an adjacent extraperi- patients with peripheral T-cell lymphoma range toneal malignant fibrous histiocytoma readily from diffuse colonic involvement to focal, and invades the colon and appears as an infiltrating from aphthae, gross ulcers, polyps, and circum- serosal tumor. ferential narrowing to simply ileocecal defor- Imaging reveals a solid, generally large tumor mity (180). An occasional lymphoma manifests suggesting a sarcoma or lymphoma. as multiple polyps in the proximal gastroin- Pathologic identification of a histiocytoma is testinal tract and numerous aphthae in the not always straightforward. At times an colon. inflammatory fibrosarcoma and a leiomyosar- An occasional colonic lymphoma presents as coma are in the differential. diffuse polyposis. These polyps tend to vary in size, and the barium enema appearance mimics Carcinosarcoma familial polyposis, although the two entities can usually be differentiated on clinical grounds. Only a few colonic carcinosarcomas have been Most often such lymphomatous polyposis rep- reported. A question is occasionally raised resents B-cell lymphoma. about whether these represent two separate col- lision neoplasms, although most carcinosarco- Sarcoma mas appear to represent differentiation of a single progeny into two cell types. The presence Leiomyosarcomas are the most common of retroviral particles in the sarcomatous cells primary colorectal sarcomas. These sarcomas of some of these tumors supports the theory of tend to be larger than carcinomas at first pres- tumor differentiation from a carcinomatous entation. After resection the 5-year survival into a sarcomatous component. depends on the tumor grade. An elevated, fungated, ulcerated tumor is a Endoscopic US identifies rectal leiomyosar- typical appearance.Most carcinosarcomas carry comas as hypoechoic tumors. a poor prognosis. 246

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Melanoma Most of these tumors are unresectable, but pal- liation of bowel obstruction is desirable. Pallia- Most of the rare primary melanomas are found tion consists, at best, of a proximal colostomy. in the rectum, and these patients present with An occasional option with a single major rectal bleeding. They tend not to obstruct. obstruction is metallic stent placement for Primary rectal malignant melanomas tend to decompression if access under fluoroscopic be polypoid or fungating, but often already guidance is feasible. Most such treatable extending to the pelvic side wall at initial pres- obstructions are in the rectum and rectosig- entation (181). A cancer is often suspected. moid, but occasionally a stent can be inserted Adenopathy is common. At times a biopsy through a more proximal obstruction (184). contains few melanocytes but considerable Many of these patients, however, have wide- inflammation, and only after tumor excision is spread metastases, including to the small bowel, a correct diagnosis made. and no viable bypass is feasible. A dual rectal melanoma and adenocarcinoma are occasionally reported; presumably such dual collision neoplasms develop by chance. Rhabdoid Tumor Both primary and metastatic melanomas have a high tumor-to-background PET activity The rare colonic malignant rhabdoid tumor is and FDG-PET scanning is useful to detect diagnosed by a pathologist detecting rhabdoid unsuspected metastases; PET is also commonly cells. This tumor is more common in the employed for follow-up after therapy. kidneys. No specific imaging features have been described.

Metastasis or Direct Invasion to Colon Neuroendocrine Tumors Metastasis to the colon is not common; more common is direct invasion from an adjacent Colonic neuroendocrine tumors are uncom- structure. Thus gynecologic malignancies mon, and some are difficult to place in proper invade the rectum, or a hepatocellular carci- perspective.An occasional colorectal poorly dif- noma invading the adjacent splenic flexure ferentiated neuroendocrine carcinoma presents results in massive bleeding, even to the point of with widespread liver metastasis. exsanguination. These tumors range from benign to malig- In a comparison of CT and MRI in predicting nant. Most are solid, intramural tumors, with bladder or rectal invasion in women with an occasional mesenteric one appearing as an uterine carcinoma, MRI was slightly, but not extraserosal tumor. statistically, superior to CT (182); both provided similar results as rectoscopy. Carcinoid A long segment of circumferential rectal wall thickening, having a rectal linitis plastica Rectal carcinoids are more common than appearance, is most often due to metastatic colonic ones; a cecal location is most common gastric cancer, but it can be found with other in the colon. Synchronous carcinoids occur causes of peritoneal carcinomatosis and rectal occasionally. Similar-appearing rectal carci- metastasis (183). Obstructions and fistulas are noids have developed in siblings. The malig- rare manifestations of lung and breast metas- nant potential of rectal carcinoids varies tases. A renal cell carcinoma is one cause of a considerably. hypervascular metastasis. Small rectal carcinoids are palpable on digital A recurrent bladder or prostatic carcinoma examination as firm nodules. Endoscopy visual- invading the rectum can simulate a rectal izes small polyps covered by normal-appearing leiomyoma or result in an annular constricting mucosa, with either erythema or a central lesion. depression occasionally being found. A malignant colon obstruction, either Carcinoid syndrome develops mostly in a primary colonic or extrinsic, most often due to setting of metastases, with only an occasional spread of a gynecologic tumor or peritoneal rectal carcinoid directly responsible for this seeding, is a difficult management problem. syndrome. 247

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Table 5.5. Clinical findings in patients with rectocolic and ileocecal carcinoids Finding Reference 185 Reference 186 Number of tumors studied 279* 36** Tumor size: >2cm 90% — Average size — 6cm Prevalence of: Metastases 61% — Nodal invasion — 22% Detection of serotonin Immunohistochemical 67% Laboratory 69% Postoperative 5-year survival rate 65% 26%

*Includes 203 patients with colon carcinoids and 76 with ileocecal carcinoids. **Includes malignant carcinoids only.

Table 5.5 summarizes the clinical findings nodular tumor nests. Transrectal US can also from two studies. Between 1964 and 1988, the often reveal depth of invasion and suggest Alberta Cancer Registry compiled 36 malignant lymph node metastasis. colon carcinoids (excluding ileocecal region and I-123-metaiodobenzylguanidine (MIBG) rectum) (186); average age at diagnosis was 68 scintigraphy evaluates metastatic carcinoids. years, and at presentation 22% of patients were Some small carcinoids have been resected already Dukes C and 86% had invaded pericolic endoscopically, although most require surgical fat. Many malignant carcinoids have already excision, similar to adenocarcinomas. metastasized at initial presentation, with the most common metastatic sites being the liver Other Tumors and lung. In fact, the presence of metastases is often the unequivocal finding establishing Schwannomas, or primary nerve sheath tumors, malignancy of these tumors. Survival with originate more often from peripheral nerves colonic carcinoids is lower than with rectal or and are rare in the colon. Most are benign. Their appendiceal carcinoids (or even with colon imaging appearance is similar to other stromal adenocarcinomas). tumors. A cystic component is occasionally Carcinoids range in appearance from a detected. simple polyp to an apple-core infiltrating tumor A rare colonic ganglioneuroma presents as mimicking an adenocarcinoma. An unusual filiform polyposis. barium enema finding in the presence of a Neurofibromatosis type 1 (von Reckling- carcinoid is colon jejunization. Such jejuniza- hausen’s disease) is discussed in Chapter 14. tion presumably is secondary to colonic wall Gastrointestinal neurofibromatosis is uncom- foreshortening induced by the desmoplastic mon and is a late manifestation of von reaction commonly associated with these Recklinghausen’s disease. Only rarely is colonic tumors. A carcinoid located in the posterior neurofibromatosis an initial presentation. rectal wall or adjacent tissues widens the pre- Gastrointestinal neurofibromas range from sacral space. solitary, to multiple, to plexiform in appearance. Transrectal US in patients with rectal carci- An occasional colonic plexiform neurofibroma noids reveals increased echogenicity and a and neuronal hyperplasia result in disordered heterogeneous internal echo pattern in some. mobility, a megacolon, and proximal bowel Small rectal carcinoids tend to be hypoechoic. dilation, similar to other causes of adynamic Pathologically, these findings are associated ileus. Some manifest through gastrointestinal with increased fibrotic interstitium around bleeding. 248

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Granular cell myoblastomas are more common in the esophagus. They are rare in the colon. Most are single, but occasional reports describe multiple tumors scattered throughout the large bowel. Dilatation Mechanical Obstruction The two most common causes of colonic obstruction in adults, namely colon cancer and diverticulitis, have already been discussed. are covered in Chapter 14. Colon obstruction in a setting of cystic fibrosis was covered in a previous section (see Cystic Figure 5.34. Cecal volvulus. CT identifies a massively dilated Fibrosis). cecum displaced to the left of midline (arrows). Dilated loops Primary causes of intestinal obstruction in of small bowel on the right are secondary to small bowel elderly patients requiring surgery are an incar- obstruction. (Courtesy of Patrick Fultz, M.D., University of cerated and colonic neoplasms. Rochester.)

Volvulus Cecal partial obstruction. Computed tomography appears to be more accurate than conventional Traditionally, cecal volvulus was suggested with radiography in suggesting the diagnosis (187), conventional radiography and confirmed either and although CT is often performed for sus- with a barium enema or colonoscopy. Most pected cecal volvulus,few studies have evaluated often cecal volvulus is idiopathic (Fig. 5.33), whether it is superior or even equal to a barium but occasionally it is induced by a more distal enema (Fig. 5.34).

A B

Figure 5.33. Cecal volvulus. A: Conventional radiograph shows a greatly dilated midabdominal loop of bowel (arrows). B: Barium enema reveals a characteristic beak sign (arrow) at the site of twist in the right colon. 249

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In distinction to sigmoid volvulus, a success- tends to recur if no resection or fixation is per- ful therapeutic barium enema or colonoscopy is formed. A surgical nonresective procedure achieved only in a minority of these patients, consists of extraperitonealization of the and most undergo surgery. sigmoid colon by placing it in the infraumbili- cal abdominal wall. Sigmoid Transverse Colon Sigmoid volvulus ranges from an acute condi- tion, often associated with strangulation, to a Transverse colon volvulus is rare. It is more chronic setting, with the patient presenting with common in women. Patients with Chilaiditi’s a gradual onset or intermittent obstruction. An syndrome appear more prone to developing a immediate concern is to ascertain that this is transverse colon volvulus; lax colonic ligaments indeed idiopathic sigmoid volvulus rather than predispose to such torsion. a sigmoid or rectal cancer-induced colonic In adults, conventional radiographs are rarely obstruction. Sigmoid volvulus occasionally diagnostic of transverse colon volvulus. Barium develops during pregnancy and after gyneco- enema findings vary; even a coil-spring appear- logic and other abdominal surgery. ance mimicking an intussusception has been Imaging findings of sigmoid volvulus are reported. familiar to most radiologists (Fig. 5.35). A CT whirl pattern consists of a twisted, dilated Other sigmoid loop and its associated vessels around the mesocolon. If the transverse colon can be Only rare reports describe splenic flexure volvu- identified on radiographs (with the patient lus. It occurs in association with systemic scle- supine), a dilated sigmoid colon located cepha- rosis and has developed in patients with a lad to the transverse colon is an accurate finding wandering spleen, generally around the splenic of sigmoid volvulus (188). pedicle. It can be associated with small bowel The preferred therapy for acute sigmoid obstruction. volvulus is decompression either by endoscopy Descending colon volvulus can develop in a or barium enema, followed, if indicated, by elec- setting of an anomalous mesocolon and a tive sigmoid resection. Simple sigmoid decom- redundant bowel. pression does relieve obstruction but volvulus Intussusception In an intussusception, a segment of bowel, the intussusceptum, invaginates into the lumen of an adjacent intussuscipiens. Any part of bowel can intussuscept, although a mobile intraperi- toneal bowel loop and its associated mesentery are most often involved. The intussusceptum usually invaginates distally, although occasional proximal invagination does occur (for example, a jejunogastric intussusception after a Billroth II operation). Intussusceptions range from transient to fixed. As discussed below, some are reduced with pressure. By its bulk, an intussusception should obstruct the bowel lumen, although in distinc- tion to pediatric patients, bowel obstruction is not a prominent feature of adult intussuscep- Figure 5.35. Sigmoid volvulus. A lateral view from a barium tions.A more serious consequence, especially in enema identifies a typical twist (arrow), shows barium in a the younger patient, is vascular occlusion of the dilated sigmoid and excludes a carcinoma as etiology for the intussusceptum, generally venous, and resultant obstruction. ischemia. 250

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Adults Intussusceptions in most adults have an identifiable lead point and range from enteroen- teric, to ileocolic, to colocolic, to . The most common lead point is a cecal adeno- carcinoma (Fig. 5.36); less common is cecal lym- phoma or a benign polyp. Rarer lead points in adults consist of pseudomembranous colitis, Meckel’s diverticulum, a rare duplication, endometrioma (Fig. 5.37), or even calcified cecal .An appendiceal polyp in a patient with Peutz-Jeghers syndrome acted as a lead point for intussusception (189). Although most colonic lipomas are intramural and sessile, they are prone to becoming pedunculated and act as lead points for an intussusception. Not all of these are at the ileocecal region; a number of sigmoid lipoma-associated sigmoidorectal Figure 5.37. Colocolic intussusception (arrows). The lead point was an endometrioma, a highly unusual source for an intussusceptions have been reported. intussusception. A rectal intussusception is usually a transient phenomenon occurring during straining, is idiopathic, and is associated with constipation. Proctography shows circular infolding of the Computed tomography and MR detect rectal wall during straining. The criteria most adult ileocolic intussusceptions but, aside defining when such infolding is abnormal are from a lipoma, identification of a lead point is not well established, and minor changes proba- difficult. At times even endoscopic biopsy fails bly are best considered normal variants, but to provide an etiology, and the diagnosis is solitary rectal ulcer syndrome (discussed later) established only after a right hemicolectomy. is in the differential diagnosis. Computed tomography findings of an intussus-

A

Figure 5.36. Colocolic intussusception with cecal carcinoma as lead point. A: Barium enema reveals the intussusceptum in the transverse colon (arrow).B: With further pressure the intussusceptum is reduced into the ascending colon. B 251

COLON AND RECTUM ception consist of a target or sausage-shaped tend to be either smoothly marginated or some- inhomogeneous soft tissue tumor. The appear- what lobular in appearance (191). ance varies depending on the relative orienta- Sigmoidorectal intussusceptions also occur tion of the x-ray beam and intussusception. in infants and children.In some,the typical clin- Colocolic intussusceptions caused by a colonic ical presentation of a palpable abdominal mass lipoma can be suggested by US; CT is diagnos- and colicky pain is absent. These intussuscep- tic if fat is detected in the lead point, although tions can be misdiagnosed as simple rectal the lack of fat in the lead point due to infarction prolapse. and necrosis of an intussuscepted tumor does Presumably a surgical consultation has been not exclude a lipoma. obtained and a surgeon has examined the child Unenhanced CT has a role if ischemia is prior to attempted intussusception reduction. suspected in adults with an intussusception; The child should be in stable condition, and CT findings of a hypodense layer in the intus- both the surgeon and the radiologist should susceptum or surrounding fluid or gas should be confident that no contraindication exists to suggest vascular compromise (190); lumen a therapeutic enema. Contraindications for obstruction is not always present in an ischemic reduction include bowel perforation, peritoni- or necrotic intussusception. tis, and hypovolemic shock. Overlying pneumatosis cystoides intesti- A long-term outcome study in children found nalis and enteritis cystica profunda are un- an overall recurrence rate of 9%, with about common associated finding of a colocolic two thirds of children having a single recur- intussusception. rence (192); reducibility was 95% for recurrent Magnetic resonance imaging also readily intussusceptions, with no perforations. Also, identifies intussusceptions, with findings recurrence did not predict an abnormal lead similar to those found with CT. Magnetic reso- point. nance imaging reveals concentric bowel rings. Imaging Pediatrics Although conventional abdominal radiographs Clinical are often obtained first, their value has been questioned. Even experienced observers often An acute ileocolic intussusception in a young differ whether in children with clinically sus- child is a common emergency. Most intussus- pected intussusception it is indeed present or ceptions occur before the age of 2 years and are absent; the best predictor of intussusception is idiopathic in origin. The rare identifiable lead a soft tissue mass and decreased large bowel gas points, more common in older children, consist (Fig. 5.38). of a Meckel’s diverticulum, polyp, or even a In some centers, US is the initial imaging duplication. Why the reported prevalence of modality of choice when suspecting an intus- intussusception is greater in some parts of the susception (Fig. 5.39). In experienced hands world is puzzling. US has a high sensitivity and specificity in The typical clinical presentation and conven- detecting an intussusception and a contrast tional radiographic findings are well known. enema is then limited to therapy. Viewed in a Occasionally encountered, however, is an atypi- transverse section, prereduction US shows an cal presentation, for instance, bilious vomiting intussusception as a doughnut or target lesion; due to an ileocolic mass resulting in extrinsic it has a reniform shape (pseudokidney is the duodenal obstruction. term often used) when viewed in longitudinal One variant is an ileoileocolic intussuscep- section. Scans close to the lead point of an tion. Prereduction findings are similar to those intussusception reveal the intussusceptum as a of an ileocolic intussusception. Once the hypoechoic central structure; scans away from intussusception was reduced to the cecum, air the lead point have a hyperechoic crescent enemas in nine children with ileoileocolic intus- appearance due to mesentery and related vessels susceptions identified the intussusceptum as being drawn in by the intussusceptum. two or more separate polypoid components, Although such a US appearance should suggest in contrast to ileocolic intussusceptums, which an intussusception, neither a target nor reni- 252

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A B

Figure 5.38. Ileocolic intussusception. A: CT scout view identifies an intussusception (arrow) in a 7–year-old. Burkitt’s lymphoma was the lead point.(Courtesy of Luann Teschmacher,M.D.,University of Rochester.) B: Intussusception in a 10–month-old infant with pain and palpable right upper quadrant mass. A conventional radiograph reveals a soft-tissue tumor in region of transverse colon (arrows). A barium enema confirmed intussusception.

form appearance is pathognomonic. Necrotiz- cal factor. A barium enema bag at 1-m elevation ing enterocolitis, volvulus, or even stool may produces greater intraluminal pressure than a mimic this appearance. typical water-soluble contrast agent or water at At times, because of obscure symptomatol- the same height. Pressure during pneumatic ogy, these patients are studied with CT.Findings reduction varies considerably. of intussusception are straightforward in most. At times US identifies fluid within an intus- Computed tomography reveals an intraluminal susception, representing trapped peritoneal tumor and a target sign–like appearance of fluid, seen on axial images as an anechoic cres- alternating layers of high and low attenuation. cent between the intussusceptum and intussus- With obstruction, more proximal bowel loops cipiens. distend with fluid. Necrosis manifests as Ultrasonography during reduction of an inflammation, loss of tissue planes, and pres- ileoileocolic intussusception reveals a complex ence of intraperitoneal fluid. frond-like appearance. The intussuscepted An extensive ileocolic intussusception small bowel is also surrounded by cecal fluid. distorts normal superior mesenteric vessel These intussusceptions are likewise difficult to anatomy. Thus with the lead point of an intus- reduce. susceptum at the sigmoid colon or distally, the superior mesenteric vein is located to the left of Contrast Agents the superior mesenteric artery. Published successful intussusception reduc- Historically, a barium enema was performed in tion rates range between 70% and 85%, with an the pediatric patient suspected of an intussus- occasional report of 90%, regardless of whether ception. The study not only established a diag- a liquid or air is used. A comparison of differ- nosis but also was therapeutic. ent contrast agents used is difficult unless the Some radiologists still use barium for reduc- procedure used is standardized. A major factor ing intussusceptions, although teaching and influencing success rates is the intraluminal pediatric hospitals have changed to a pneumatic pressure achieved rather than any other techni- technique. 253

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Figure 5.39. Ileocolic intussusception due to large lymph nodes in a 10–year-old. A: CT detects an intraluminal right colic tumor (arrows) suggesting an intussusception. The intussusceptum is seen as a target lesion on a transverse US scan (B) and as an oval tumor on a longitudinal scan (C).Surgery revealed enlarged nodes as a lead point but no neoplasm was identified.(Courtesy of Luann A Teschmacher, M.D., University of Rochester.)

B C

A pneumatic reduction of intussusception is tion increased to 91% after a policy of up to safe and successful in most children. Although three trials was instituted (193). fluoroscopy is useful for this procedure and Some radiologists perform pneumatic reduc- is employed by many radiologists, a lead point tion under US control. In patients who under- is difficult to identify. Thus even with success- went 52 US-guided pneumatic intussusception ful reduction, the presence of a tumor lead reductions, the overall success rate was 92% point is not excluded. Still, many radiologists (194); a pressure of 60mmHg was maintained believe that pneumatic reduction is quicker, for 30 seconds, and if an intussusception failed safer, and more effective than hydrostatic to reduce, the procedure was repeated at a pres- reduction. sure of 120mm Hg. Perforation occurred in two Reduction success rate varies with the dura- others. The published data of pneumatic reduc- tion of signs and symptoms. Thus success rate tion under US control are difficult to place in the for air reduction was 89% for those sympto- proper perspective because of the subjective matic for <12 hours, 83% for those with symp- nature of many of these studies. toms for 12 to 24 hours, and 74% for those In some parts of the world pneumatic reduc- symptomatic for >24 hours (193). Several trials tion is performed with no imaging, and the of air reduction increase the success rate. A success of reduction is evaluated purely on clin- success rate of 70% with one trial of air reduc- ical grounds. 254

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Color Doppler US evaluates whether blood the rectosigmoid without invasion. A barium flow is present in an intussusception. The enema is diagnostic. success rate for air reduction is significantly A pregnant patient with an ileal pouch–anal greater in those children with blood flow in anastomosis presented at 36 weeks’ gestation the intussusception than in those with absent with bowel obstruction (196); the obstruction flow. Lack of Doppler evidence for blood flow, cleared after delivery. however, should not be a contraindication to attempted reduction, and practical applica- Obstruction by Gallstones tion of such Doppler study remains to be established. ileus most often obstructs in the A more recent technique is US-guided intus- ileum (discussed in Chapter 4). With a chole- susception reduction using a saline enema or cystoduodenal fistula, if a stone manages to pass Hartmann’s solution. The sonographic criteria through the ileocecal valve, colonic gallstone of intussusception reduction include an initial ileus occurs almost always only proximal to a target sign that is later no longer identified, stricture. visualization of the ileocecal valve, and fluid Another scenario of colonic gallstone ileus refluxing into small bowel; this technique has occurs if a cholecystocolic fistula develops; a success rate of over 90% in reducing an obstruction by the gallstone most often is in the intussusception. sigmoid colon. If the obstruction is incomplete, a barium enema identifies a cholecystocolic fistula. Complications Obstruction Due to In some infants only partial intussusception reduction is achieved. In these infants, instead Motility Abnormalities of performing immediate laparotomy, in con- Pseudo-Obstruction (Ogilvie’s Syndrome) sultation with the surgeon and if the infant is clinically stable, another attempt at intussuscep- Etiology tion reduction may be appropriate. A number of etiologies have been proposed for The risk of bacteremia during intussuscep- acute colonic pseudo-obstruction (Ogilvie’s tion reduction is low. syndrome), including an imbalance between What are the sequelae of a perforation during sympathetic inhibitory and parasympathetic an intussusception reduction? In 14 perfora- excitatory colonic innervation. It occurs most tions (seven using barium and seven air) all often after surgery or trauma (Table 5.6). children with barium reduction required bowel resection, but only four of the seven with air required resection (195); in addition, the Table 5.6. Conditions associated with Ogilvie’s syndrome anesthesia time was longer and hospital stay Common longer in the barium group. Of interest is that Recent surgery perforations are through necrotic bowel only Recent trauma in a minority of these children; presumably Severe medical condition increased pressure plays a major role in these Uncommon perforation. In general, all other factors being Postcesarean section equal, the perforation rate is probably similar Leukemia regardless whether barium or air is used. von Recklinghausen’s disease Multiple endocrine neoplasia (MEN) syndrome type 2 Botulism in infants Herpes zoster infection Extrinsic Obstruction Hypothyroidism Occasionally a distended bladder compresses Myotonic dystrophy the rectosigmoid against the sacrum and Drug therapy obstructs on either an acute or chronic basis. Imipramine Tocolytic therapy Similarly, some gynecologic tumors compress 255

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Some chronically hospitalized or bedridden Untreated, Ogilvie’s syndrome has progressed patients have a chronic megacolon or megarec- to perforation and an acute abdomen. tum, generally of idiopathic etiology. Manome- try in these patients reveals abnormal colonic Chagasic tonicity. Histology of resected specimens from patients with idiopathic megarectum and Chagas’ disease is a chronic infection caused megacolon reveals hypertrophy of muscularis by the parasite Trypanosoma cruzi,which is mucosae and muscularis propria; those with an endemic in rural regions of Latin America. A idiopathic megarectum tend to have decreased chronic phase develops several decades after innervation density of the longitudinal muscle. initial infection, most often manifesting Recurrent acute colonic pseudo-obstruction through cardiac abnormalities. Colonic abnor- in a young patient with no evident risk factors malities consist of decreased motility and was eventually ascribed to toxoplasmosis tonicity, identified as a megacolon. These infection (197); adrenergic bowel denervation patients develop small bowel bacterial over- was believed to be caused by toxicity or cross- growth with resultant complications. reaction between a toxoplasma antigen and the patient’s immune system. Systemic Sclerosis (Scleroderma) Colorectal dysfunction is common in patients Imaging with systemic sclerosis. Hypotonia and stasis develop in some. Constipation is common, The conventional radiographic appearance of but, paradoxically, incontinence is also not Ogilvie’s syndrome mimics distal colonic uncommon. obstruction. Thus if the diagnosis is in doubt, a T1- and T2-weighted SE MRI magnetization limited barium enema is indicated and should transfer contrast-weighted and dynamic differentiate between these conditions. gadolinium-enhanced images in 11 of 14 Instead of a barium enema, two additional patients with scleroderma and fecal inconti- conventional radiographs often suffice: a right nence revealed forward deviation of an atro- lateral decubitus view of the abdomen followed phied internal sphincter that had decreased by a prone lateral view of the pelvis. With these contrast enhancement (198); for comparison, two additional views gaseous distention of the patients with incontinence alone showed no rectum can be achieved in most patients with internal sphincter deviation or decreased vas- pseudo-obstruction, while in patients with cularity but did have significant reduction in mechanical obstruction such distention is not external sphincter mass. found. Although the cecum is generally most dilated in Ogilvie’s syndrome, occasionally some other colonic segment is involved. The rectum tends Diverticula to be collapsed. Colonic

Therapy Colonic diverticula represent outpouchings in the bowel wall. In the past, a distinction was Ogilvie’s syndrome has been treated success- made between true and false diverticula (pseu- fully with a parasympathomimetic drug such as dodiverticula), but common indiscriminate neostigmine. The success of such therapy sug- usage has made any such distinction moot. gests that Ogilvie’s syndrome is a result of exces- Prevalence of colonic diverticula varies con- sive parasympathetic suppression rather than siderably throughout the world. Their preva- sympathetic overactivity. Colonoscopic decom- lence is increasing in some populations. pression has a high success rate, although some Right-sided colonic diverticula are more patients required multiple decompressions. A common in Asia than in the West. decompression tube positioned in either the Occasionally encountered are calcified stones right colon or transverse colon appears to be within a diverticulum. Presumably these stones equally successful. form as a result of stasis. Superficially such 256

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right-sided diverticular stones mimic gallblad- is unknown, although several theories are pos- der stones or renal stones. tulated: First, a check-valve mechanism in the In rare instances a diverticulum intussuscepts diverticular neck allows colonic content to enter or inverts into colonic lumen and simulates a but not exit.Or,a localized diverticular infection polyp. Some of these patients have undergone results in an abscess that eventually communi- surgery or colonoscopy because the diverticu- cates with colonic lumen. Although less likely, lum could not be distinguished from a polyp. such a cavity may also represent sequelae of a Some of these inverted diverticula have an communicating duplication cyst. In either case, umbilication that represents the en face diver- some of these cavities enlarge to giant propor- ticular opening. Computed tomography of these tions. Histologically, these giant diverticula do inverted diverticula reveal a central contrast not have a mucosal lining, with the wall con- collection within the lumen, presumably within sisting mostly of fibrotic tissue, thus suggesting the diverticulum. a contained perforation as their etiology. Ultrasonography does not readily identify Patients range from asymptomatic to those colonic diverticula. When seen, diverticulitis presenting with bleeding or an acute abdomen. rather than should be suspected. An occasional giant colonic diverticulum perfo- rates and results in a . Rectal Other rare complications include an associated carcinoma, small bowel obstruction, or even Rectal diverticula are uncommon and, in volvulus. general, tend to be larger than the cor- These uncommon lesions can be suspected responding sigmoid ones. These diverticula with conventional radiography and are diag- tend to be more common in scleroderma nostic with a barium enema when barium patients. flows into the diverticulum, thus establishing its colonic communication (Fig. 5.40). Imaging Giant Diverticula shows a large gas collection, usually close to the sigmoid colon. The diverticular wall tends to be Giant colonic diverticula are sufficiently rare thin and smooth. Horizontal x-ray beam radi- that individual reports are still being published. ographs often reveal a gas-fluid level. The diver- Most occur in the sigmoid colon. Their etiology ticular wall shows no CT contrast enhancement,

A B Figure 5.40. Giant sigmoid diverticulum. A: A conventional radiograph identifies a large gas-filled structure (arrows). B: A barium enema confirms a diverticulum (arrows) and establishes its communication with colon. 257

COLON AND RECTUM except if surrounding inflammation is present. An anterior enterocele, or anterior vaginal Some rare chronic diverticula contain wall hernia containing small bowel, develops in calcifications within their wall. some women who undergo a cystectomy for A thick-walled cavity or any nodularity intractable interstitial cystitis. should suggest a necrotic tumor rather than a Evacuation proctography is the examination giant diverticulum. A communicating duplica- of choice to detect the more common posterior tion is rare in the sigmoid, usually is on the enterocele consisting of prolapsed small bowel mesenteric side, is seen in a younger patient interposed between vagina and rectum. Small population, and histology should reveal an bowel and vaginal opacification are needed epithelial lining containing all layers of the during this study. Some enteroceles become colonic wall. evident only at the end of evacuation or on Most giant colonic diverticula are resected. postevacuation radiographs. Of interest is that physical examination detects only half of ente- roceles found on proctography (199); the Evacuation Disorders reverse is also true—some enteroceles detected by physical examination are not identified at Lax pelvic floor muscles and an abnormal pelvic proctography. floor descent are evident in some patients with Vaginal US is helpful to detect a posterior evacuation disorders, leading to multiorgan enterocele; if one is present, bowel is visualized interrelated abnormalities; these complex pelvic in the rectovaginal space, especially when floor abnormalities, found mostly in women, are bearing down. This examination is highly discussed in Chapter 12. sensitive and specific in detecting these Discussed here are primarily evacuation enteroceles and is an alternative to evacuation disorders, which in themselves are a diverse proctography. and complex group of conditions manifesting mostly by rectal pain and difficulty in evacua- Rectocele tion. Rectal incontinence is the other extreme. The nomenclature for various abnormal Although constipation is common in patients findings is still evolving, and authors often with a rectocele, in some patients even a large describe these conditions based on the primary rectocele is not associated with impaired abnormality detected. evacuation. Also, placing rectoceles in clinical Traditionally, proctography evaluated both perspective can be difficult; constipation is not structural and function, although dynamic MRI always relieved after rectocele repair. is assuming a primary role in evaluating evacu- ation disorders. Anterior Rectocele Enterocele An anterior rectocele consists of a bulge in the anterior wall of the rectum during straining. One of the causes of a widened rectovaginal Although a mild bulge is a normal finding, a space is a peritoneocele, defined as herniation of typical definition is that the bulge should be the posterior-inferior peritoneal space (cul-de- >2cm in extent to be considered a rectocele. sac) into a recess between the rectum posteri- Most rectoceles are reduced at rest. They are orly and vagina or bladder anteriorly. Any more common in women, probably due to a adjacent intraperitoneal structures can be weakness of the rectovaginal septum. involved, although most often small bowel is Some investigators subdivide anterior recto- involved and is then called an enterocele. Pro- celes into two groups: distention and displace- lapse of redundant sigmoid (sigmoidocele) is ment. Manometry in patients with each type less common. Some of these are capable of revealed a significantly higher anal pressure and partially obstructing the rectum. A distended a more impaired rectoanal inhibitory reflex in rectum may conceal a peritoneocele and an the distention group than in controls or the enterocele; a radiograph taken with the rectum other group (200); patients in the displacement collapsed should detect this condition. group have a lower anal pressure, and proctog- 258

ADVANCED IMAGING OF THE ABDOMEN raphy at rest and during evacuation show a condition is one syndrome or encompasses a significantly higher anorectal angle and a more number of disorders is conjecture. Diffuse abnormal pelvic floor descent than in the dis- pelvic floor weakness involving genitourinary tention group or in controls. Overall, distention structures is found in some women. Chronic rectoceles have pelvic floor , while constipation, evacuation abnormalities, and displacement rectoceles show a descent in the rectal prolapse are typical presentations. Con- pelvic floor. fusing the issue, some authors find rectal bleed- Currently a suspected rectocele or sigmoido- ing to be common, but others believe it is an cele is most often studied with evacuation proc- uncommon finding. tography. Whether a rectocele is detected or not Pressure necrosis and mucosal injury during is mostly independent of contrast agent viscos- rectal prolapse and intermittent intussusception ity. Pelvic MRI, including MR proctography, appear to play a role, although the pathophysi- often provides additional information. Proctog- ology is probably multifactorial. Typical raphy detects most rectoceles, although a histopathologic findings consist of focal majority are also detected on physical examina- mucosal distortion, muscularis mucosa pro- tion (201); whether barium is trapped in a rec- liferation, and obliteration of lamina propria. tocele depends mostly on its size. An ulcer, accompanied by granulation tissue, is A rectocele tends to bulge only during strain- usually located anterior in the rectum but at ing. Among patients with rectocele shown by times extends circumferentially. proctography, 60% also had paradoxical anal Sigmoidoscopy is generally noncontributory sphincter relaxation (202). in these patients, aside from providing a biopsy In addition to enteroceles and rectoceles, and excluding other abnormalities. In some widening of the rectovaginal space on straining patients manometry reveals decreased external is occasionally due to a peritoneocele. Sig- sphincter tone during straining, a nonspecific moidoceles are uncommon. finding. Biopsy in patients believed to suffer from Posterior Rectocele solitary rectal ulcer syndrome revealed a soli- tary ulcer in 78%, multiple ulcers in 11%, gran- Posterior rectal outpouchings include posterior ular proctitis in 7%, and rectal inflammation in rectoceles and ischiorectal hernias. Posterior 4% (203); although voiding proctography or perineal rectoceles are outpouchings of missed some ulcers, it identified rectal intussus- the lower posterior rectal wall through a levator ception in 41%, rectoanal intussusception in ani muscle defect, usually present only during 26%, external rectal prolapse in 22%, and straining. An ischiorectal hernia is seen as a mucosal prolapse in 30%. Only one patient had posterolateral outpouching; these are present at a rectocele. In a majority of patients videoproc- rest. tography showed that the ulcer wall was first to Posterior rectal herniation also develops after invaginate. resection of sacral tumors, such as a chordoma. Solitary rectal ulcer syndrome and an inflammatory cloacogenic polyp have similar Rectal Prolapse/Solitary Rectal histopathologic findings; both are located ante- rior in the rectum and both tend to be associ- Ulcer Syndrome ated with rectal prolapse. Clinical Previous therapy for intractable symptoms included rectocolic resection, a procedure rarely Abnormal puborectalis muscle contraction and performed today. After elastic binding for rectal rectal wall prolapse or intussusception are mucosal prolapse, follow-up voiding proctogra- often implicated in the pathogenesis of solitary phy revealed prolapse remission in most rectal ulcer syndrome,a benign condition found patients. mostly in adults. Prolapse ranges from internal to external; the term intussusception is appro- priate if it is circumferential. Complete rectal Imaging prolapse is a clinical diagnosis and generally A double-contrast barium enema, with empha- needs surgical correction. Whether this sis on the anterior rectal wall, is useful to detect 259

COLON AND RECTUM an ulcer and the sequelae of inflammation, but seen with an inflammatory cloacogenic polyp; an evacuation study is necessary to evaluate some mimic a rectal adenocarcinoma. functional abnormalities. Imaging is also often Voiding videoproctography is the imaging requested prior to surgical repair to evaluate the modality of choice for suspected rectal pro- rest of the large bowel. lapse. Prolapse originates in the midrectum as In spite of its name, solitary rectal ulcer syn- an intussusception varying in length. Proctog- drome does not always present with an ulcer, raphy reveals rectal mucosal prolapse as a soft nor is it always solitary. A common imaging tissue bulge into the rectal lumen, more evident appearance is that of nodularity or an anterior during straining and evacuation than during rectal wall irregular polyp. Similar findings are rest (Fig. 5.41). Mucosal prolapse is more

A B

C D

Figure 5.41. Rectal prolapse.A: Initial lateral view is unremarkable.B: Prolapse becomes evident with early straining.Further strain- ing reveals marked prolapse (C, cursor), also identified on a frontal view (D). (Courtesy of Arunas Gasparaitis, M.D., University of Chicago.) 260

ADVANCED IMAGING OF THE ABDOMEN common than intussusception (204).Associated other abnormalities are common and include rectocele, perineal descent syndrome, puborec- talis muscle syndrome, and diastasis, the latter identified with dynamic CT. At times endorectal US is helpful. Ultra- sonography reveals an inhomogeneous and thickened submucosa in the internal and exter- nal sphincter regions; the ratio of external to thickness is reduced in these patients and muscle hypertrophy identified by US appears useful in some in sug- gesting the diagnosis.

Puborectalis Syndrome Puborectalis syndrome is used to describe incomplete relaxation or paradoxical contrac- tion of the puborectalis muscle during evacua- tion, often with resultant outlet obstruction. At times an isolated finding, it is one of a spectrum Figure 5.42. Nonrelaxing puborectalis muscle (arrow).This is a of abnormalities detected in constipated contributing factor in solitary rectal ulcer syndrome. (Courtesy patients. The term pelvic floor dyssynergy is of Arunas Gasparaitis, M.D., University of Chicago.) used by some to encompass a more complex set of findings. Primary symptom of puborectalis syndrome consists of incomplete or intermittent evacua- results), the importance of a particular amount tion.Voiding proctography reveals an abnormal of change is questionable. Anorectal angle puborectalis muscle impression along the pos- measurements provide conflicting data, with terior rectal wall, a reduced change in anorectal some studies revealing no significant difference angle during straining, and prolonged barium between patients with anismus and controls and pooling in the rectal ampulla; manometry others concluding that in most patients with detects an increase in incontinence the anorectal angle is increased at pressure under straining in about two thirds of rest. these patients (Fig. 5.42). Some patients also One study found that 90% of patients have associated rectal mucosal prolapse and a with impaired proctographic evacuation had rectocele. anismus at subsequent anorectal physiologic testing (205). Anismus/Incontinence Endoanal US identifies anal sphincter defects in approximately two thirds of incontinent Whether anismus and puborectalis syndrome patients (206); these findings are difficult to are the same entity is conjecture. Many authors place in the proper perspective because in this discuss them together. Some patients with func- same study the prevalence of anal sphincter tional outlet obstruction have a megarectum, defects in continent patients was 43%. rectocele, rectal intussusception, mucosal pro- Endovaginal US appears to be as reliable as lapse, or abnormal perineal descent. Reduced endoanal US in evaluating the anal sphincter change in anorectal angle between rest and but endovaginal US is more accurate for peri- evacuation is used by some as a criterion for anal inflammatory disease (207). defining functional outlet obstruction. Whether endoanal US or MR is superior is Although the anorectal angle does change not clear. A retrospective study in women with during straining and voiding (and viscosity of concluded that in detecting the contrast medium used influences the external and internal sphincter lesions 261

COLON AND RECTUM endoanal MRI agreed better with subsequent Table 5.7. Conditions associated with colonic perforation surgical findings than did endoanal US (208); Mechanical obstruction (obstructive ileus) endoanal US was not accurate in identifying Neoplasm external sphincter thinning, a finding Benign stricture/obstruction confirmed in another study (209). Yet another Volvulus study found not only endoanal US and MRI to Herniation be equivalent in detecting external anal sphinc- Intussusception ter defects, but also US was superior for internal Fecal impaction anal sphincter defects (210). Adynamic ileus Often a combination of studies is helpful in Inflammation/infection these patients. As one example, proctography in Ogilvie’s syndrome 38 patients with incontinence identified rectal Toxic megacolon mucosal prolapse (n = 12), rectocele (n = 10), Necrotizing enterocolitis perineal descent syndrome (n = 8), and external Typhlitis rectal prolapse (n = 3); endoanal US identified Ischemic ileus 15 sphincter ring interruptions (12 hypoechoic, Severe malacoplakia two mixed, and one hyperechoic) and internal anal sphincter thinning in five; perineography Instrumentation revealed a cystocele in five and a cystourethro- Endoscopy Barium enema cele in one; and manometry showed sphincter Biopsy hypotonia at rest in 15 (211). Placing these findings in a proper perspective, however, is Foreign body often challenging. Toothpick A separate group of patients with fecal incon- Other sharp objects tinence consists of those with congenital anom- Drug therapy alies, such as spina bifida. Some of these often Ehlers-Danlos syndrome young patients are successfully treated with per- cutaneous cecostomy tube placement, a proce- dure having few complications.

Perforation generally in the sigmoid colon. Among ingested bones, chicken bones seem to predominate. Some of conditions associated with colonic per- Spontaneous rectal perforation is rare; one foration are listed in Table 5.7. Among common unusual rectal rupture led to etiologies for colonic perforation, patients with evisceration through the anus (212). a perforating carcinoma have a high mortality. In distinction to upper gastrointestinal per- An unusual cause is due to paclitaxel therapy; foration from peptic ulcer disease, which tends these perforations appear to be a direct drug to result in small amounts of intraperitoneal effect causing mitotic arrest of the gastroin- gas, colonic perforations more often lead to a testinal epithelium. The prevalence of such per- large pneumoperitoneum. Exceptions, however, foration is not known, although it is associated are common. Also, some colonic perforations with a high mortality rate. manifest with an abscess rather than pneu- Ehlers-Danlos syndrome type IV consists of moperitoneum. an inherited collagen disorder. The syndrome can be confirmed by culture of skin fibroblasts. These patients have a defect in either the syn- Nonspecific Ulcer thesis or structure of type III procollagen and are prone to spontaneous aortic, small bowel, Grouped under this heading are those colonic and colonic rupture. Recurrent colon perfora- ulcerations believed not to be associated with tions develop in patients with this syndrome. other diseases. Some of these ulcers presumably A number of reports describe colonic perfo- are ischemic in etiology. Few publications exist ration by an ingested sharp bone or toothpick, on this topic. 262

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Fistula compared US and MR against fistulography, preferring to use surgical findings as their gold Diagnostic modalities to evaluate fistulas standard. Yet the reliability of surgery as a stan- include fistulography for cutaneous fistulas, CT, dard has been questioned; using long-term MRI using an endorectal coil, and proctosig- patient outcome as a gold standard, preopera- moidoscopy, with endorectal US having a major tive contrast-enhanced MR grading achieves role in perirectal fistulas. Nevertheless, MRI has higher sensitivity and specificity than surgical gradually achieved preeminence. exploration in predicting patient outcome At times a two-part CT study is found (213); in this study surgery was performed advantageous when searching internal com- without knowledge of MR findings, and munication for cutaneous fistulas; first, con- outcome was considered unsatisfactory if addi- ventional CT is obtained after filling the tional surgery was necessary. appropriate bowel with contrast, followed by Is endoanal US superior to a transperineal US concentrated contrast injection into any visible approach? Some patients cannot tolerate anal fistulas and rescanning using wide window coil insertion. In some patients, such as those settings. with Crohn’s disease, fistulas tend to extend Colonoscopy is insensitive in identifying beyond the field of view of an endoanal coil. colonic fistulas. Gray-scale US identifies fistulas as a thin hypoechoic line. Endocavitary US is more sensitive in detecting intersphincteric than Perianal Fistulas transsphincteric fistulas (214). Overall, however, transperineal US in men and both endovaginal Perianal fistulas are either anovaginal, associ- and transperineal US in women appear prefer- ated with Crohn’s disease, or cryptoglandular in able to endoanal US when evaluating perianal origin. Most perianal infections originate in inflammation. Hydrogen peroxide introduced intersphincteric anal glands located close to the into the fistula tract through the external dentate line and spread from there. The Parks opening appears of limited additional value classification of perianal fistulas is based on except in assessing an internal opening (215). a fistula track relationship to anorectal muscu- Although some studies concluded that lature and consists of four main types: (1) endorectal US detects more fistulas than MRI, a superficial or low, (2) intersphincteric, (3) prospective study of MRI [1.0-T axial and transsphincteric, and (4) suprasphincteric or coronal T2-weighted turbo spin echo (TSE) and high fistula. A horseshoe fistula extends turbo-STIR sequences] and US (10-mHz rotat- circumferentially. ing endoanal probe) of patients with perianal Almost all external sinus tracts and fistulas fistulas achieved an 84% sensitivity for MRI and located close to the posterior midline are asso- 60% for US, and specificities of 68% and 21%, ciated with a simple superficial or intersphinc- respectively, in detecting and classifying these teric fistula; on the other hand anterior and fistulas (216). posterolateral external sinus tracts and fistulas An MR endoanal coil was superior to a pelvic tend to be complex and often extend phased array coil in evaluating most fistulas, the transsphincteric or are suprasphincteric in their exception being supralevator fistulas and in course. These fistulas must be differentiated evaluating subcutaneous extensions where a from necrotic tumors, infections such as actin- phased array was superior (217); sagittal and omycosis, pilonidal cysts, and similar disorders. coronal plane images are very helpful. MR using Any associated abscesses also need be identified rectal contrast identifies more pelvic and by imaging. perirectal fistulas than precontrast imaging. What are the relative roles of US and MRI? No As an example of the optimistic results obvious answers have emerged, although achievable with MR, high-spatial-resolution current evidence suggests that, overall, MR is MRI using a quadrature phased-array coil superior to US; also, MR is the more active reached 100% sensitivity and 86% specificity for current research front. detecting fistulous tracks; 96% and 97%, respec- Fistulography is traditionally used to study tively, for associated abscesses, 100% and 100%, sinuses and external fistulas. Few studies have respectively, for horseshoe fistulas, and 96% and 263

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90%, respectively, for internal openings (218). Even when using a low field (0.1-T) MR unit, results have agreed with the final diagnosis in over 95% (219). Nevertheless, some MR studies are more pessimistic when evaluating the site and extent of a fistula; for instance, in patients with subsequently confirmed fistula-in-ano, MRI detected only 42% to 50%, depending on the radiologist’s experience (220).

Genitourinary Tract Fistulas Renocolic Fistula Renocolic fistulas are usually secondary to renal inflammation or neoplasms. An occasional patient with xanthogranulomatous pyelone- phritis and ureteric obstruction develops a renocolic fistula. An antegrade or retrograde pyelogram should identify these fistulas. Com- Figure 5.43. Rectovaginal fistula (arrow) secondary to lym- puted tomography usually reveals a complex phomatous infiltration. air-fluid collection within either the kidney or the adjacent soft tissues.

nism presumably exists, and in any one patient Urethrorectal Fistula not all three studies identify a fistula. Rare urethrorectal fistulas consist of fistulas communicating between the prostate or bul- Rectovaginal Fistula bomembranous urethra and rectum. Trauma from missiles is a not uncommon cause of Most rectovaginal fistulas are secondary to birth these fistulas. A number of these patients have trauma, gynecologic surgery, or pelvic radia- had prior surgery or complex anoperineal tion. A rare cause is pelvic amebiasis or actino- suppuration. mycosis. Diverticulitis predominates as a cause Detection of urethrorectal fistulas is straight- of colovaginal fistulas. forward, either via a urethrogram or a contrast Either a barium enema or vaginogram enema. identifies these fistulas (Fig. 5.43). Pelvic MRI is Some of these fistulas close spontaneously useful to define involved tissue planes. T2- after a more proximal-sigmoid colostomy and weighted images identify rectovaginal fistulas as suprapubic cystostomy; others require surgical hyperintense linear defects. Most internal correction. opening can be identified. A nitinol-silicone double-disc device was inserted transrectally into a rectovaginal fistula Colorectal Vesical Fistula and the fistula occluded (221). Such an Most enterovesical fistulas are secondary to occluding device appears useful in a setting of inflammatory bowel disease or diverticulitis, tumor, pelvic radiation, and reluctance for with an occasional one originating from a colon repeat surgery in someone with limited life carcinoma, bladder carcinoma, or other expectancy. neoplasms. Pneumaturia is common but not universal in patients with a colovesical fistula.At Other Fistulas times cystitis is the primary presentation. Most colovesical fistulas can be identified by Some iatrogenic gastrocolic fistulas are created barium enema, cystography, or cystoscopy. In due to inadvertent transverse colon puncture some patients a one-way check valve mecha- during percutaneous gastrostomy. An occa- 264

ADVANCED IMAGING OF THE ABDOMEN sional duodenocolic fistula is secondary to difficult to identify on conventional radi- colonic Crohn’s disease or a neoplasm. A peptic ographs. Ultrasonography of cannabis packages ulcer–induced fistula to the colon is rare. Most reveals round hyperechoic structures. cholecystocolic fistulas are secondary to chole- cystolithiasis. Resulting inflammation and fibrosis, generally involving the hepatic flexure or proximal transverse colon, mimics the Vascular Lesions (Bleeding) barium enema appearance of a primary colon Discussed here are those entities manifesting adenocarcinoma. primarily by bleeding. Ischemic colitis has been One complication of interleukin-2 therapy is discussed in a previous section. bowel perforation. The etiologies of rectal bleeding in adults are wide-ranging (Table 5.8) and differ between pediatric patients and adults; in pediatrics it is Pneumatosis Coli worthwhile to consider causes of rectal bleeding by age (Table 5.9). Pneumatosis cystoides intestinalis is discussed in more detail in Chapter 4. Pneumatosis coli represents pneumatosis Detection cystoides intestinalis limited primarily to the colon. Similar to small bowel, pneumatosis coli Contrast-enhanced CT is at times worth-while can be subdivided into ischemic and non- in a patient with suspected lower gastrointesti- ischemic (benign) causes. It is characterized nal bleeding. Contrast extravasation is obvi- by multiple gas-filled cysts within bowel wall. ously diagnostic, but bowel wall contrast- Pneumatosis most often affects the left colon; a enhancement or presence of a focal lesion also redundant sigmoid colon is a common ancillary point towards a bleeding site. finding. An occasional colonic intussusception Technetium-99m–red blood cell scintigraphy is associated with pneumatosis cystoides is often employed as a screening examination intestinalis. for patients with suspected colonic bleeding. Pneumatosis coli is readily diagnosed with Should a nuclear medicine bleeding scan be conventional radiography. A barium enema or obtained and mesenteric arteriography per- CT confirms the intramural location for these gas collections. Endosonography reveals hyper- echoic collections with acoustical shadowing. Table 5.8. Etiologies of rectal bleeding in adults Colonic Diverticulosis Body Packer Inflammatory bowel disease Ischemic colitis Smuggling of cocaine or heroin concealed in the Infectious colitis gastrointestinal tract is not new. The drugs are Neoplasms typically wrapped in cellophane or condoms and swallowed. In general, rupture of a single /arteriovenous malformations package is above the toxic dose and is fatal. At Portal hypertension—colonic varices times these packages also obstruct the bowel. Small bowel Most of these “mules”are treated conservatively, Inflammatory bowel disease although an occasional one requires surgery. Angiodysplasia/arteriovenous malformations Both US and conventional abdominal Diverticular causes radiographs readily detect swallowed drug Meckel’s diverticulum related Neoplasms packages. Conventional radiographs and CT identify cannabis and cocaine packages as well- Proximal to ligament of Treitz marginated, rectangular, high-density struc- Peptic ulcer disease tures surrounded by a gas halo,called the double Angiodysplasia/arteriovenous malformations condom sign; heroin packages are seen as poorly Dieulafoy lesions Portal hypertension—gastroesophageal varices outlined structures resembling stool and are 265

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Table 5.9. Rectal bleeding in pediatric patients Age Common etiology Less common etiology Neonate (0–30 days) Anal fissure Infectious enteritis Necrotizing enterocolitis Midgut volvulus Allergic colitis Infant (30 days–1 year) Intussusception Meckel’s diverticulum Anal fissure Infectious enteritis Allergic colitis Polyp Henoch-Schönlein purpura Child and adolescent Meckel’s diverticulum Henoch-Schönlein purpura Polyp Vascular malformation Anal fissure Coagulopathy Infectious enteritis Hemolytic-uremic syndrome Inflammatory bowel disease

formed only if the scan is positive? The primary patients. Even hemorrhage from a large vessel purpose of such a policy is to increase the per- can be arrested. Postembolization ischemia is centage of positive arteriograms, yet one retro- rarely an issue with this technique. spective study concluded that a prior positive One refinement is superselective microcoil bleeding scan did not increase the odds of embolization, with embolization performed at obtaining a positive angiogram (222), a finding the vasa recta or the marginal artery of Drum- at odds with a number of other studies. Thus mond level. In one study, bleeding was arrested arteriography in patients with suspected acute on a long-term basis in over 80% of patients gastrointestinal bleeding detected bleeding in (224). Hemostasis can be expected in all except 22% of studies, but after instituting a protocol those with a dual blood supply to the bleeding requiring positive scintigraphy before perform- site, yet even in the latter significant reduction ing arteriography, the positive arteriography of bleeding is achieved. Occasional bowel rate increased to 53% (223). ischemia, rebleeding, and even infarction are In patients with suspected acute lower gas- recognized complications of this procedure. At trointestinal bleeding, Tc-99m–red blood cell times superselective embolization includes a scintigraphy achieves >80% sensitivity in combination of coils, polyvinyl alcohol, and detecting bleeding and in those with positive gelatin sponge particles. scan localizes a bleeding site in about 70%. Colonoscopy can potentially identify a Diverticular Bleeding colonic bleeding site. A practical limitation exists if blood and blood clots obscure adequate A typical diverticular bleed tends to be massive visualization. Also, complete colonoscopy is and arterial, and it stops spontaneously. Often necessary because in up to one third of patients little other evidence of diverticulitis is present. a bleeding site is in the cecal region. Past teaching was that bleeding is due to erosion of a small artery overlying the diverticulum, but Therapy whether such erosions differ from a Dieulafoy lesion is not clear. After mesenteric angiography identifies a bleed- Right-sided diverticulosis tends to present ing site, immediate therapeutic options include with massive rectal bleeding more often than arterial embolization and infusion of vaso- left-sided disease, yet in general, cecal bleeding pressin. Arterial embolization is viable therapy is more difficult to control than more distant for most acute lower gastrointestinal bleeding. bleeding. The clinical success of embolization, judged by In patients without definitive therapy, recur- no rebleeding, is achieved in about 90% of rent hemorrhage occurs in about 10% at 1 year. 266

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Angiodysplasia they are detected with contrast-enhanced imaging. Among a healthy, asymptomatic population prevalence of angiodysplasia is <1%. These ectatic veins, venules, and capillaries probably Varices develop secondary to local degeneration, espe- cially with aging. A deficiency of collagen type Most colonic varices are associated with portal IV is found in mucosal vessels in angiodyspla- hypertension. Why only some patients develop sia. They occur in both the small and large colonic varices is not clear, although the pre- bowel. Most, however, are smaller than 10mm valence of these varices increases in those and are located in the right colon. They range who have had prior transection and devas- from single to multiple. Most manifest in the cularization of esophageal varices, esophageal elderly, although angiodysplastic hemorrhage sclerotherapy, or thrombosis of coronary does occur in young patients. Earlier reports and azygous drainage veins. Congenital colon suggested an association between angiodyspla- varices are rare; in the absence of portal hyper- sia and aortic stenosis, but more recent studies tension resection of such varices is curative. do not confirm such a link. Varices have developed secondary to mesenteric Unusual associations of rectal and sigmoid venous obstruction and,rarely,with splenic vein colon angiodysplasia-like lesions include a 12- thrombosis.Also rare are idiopathic colonic and year-old boy with Klippel-Trenaunay-Weber mesenteric varices. syndrome who developed hematochezia (225). Bleeding from colorectal varices can be The presence of colon angiodysplasia, small massive; portal hypertension needs to be bowel lymphoma,and duodenal carcinoid in the excluded in these patients. same patient suggests a more than fortuitous Colonic and perirectal varices can be diag- association (226). nosed with contrast-enhanced CT. What is sur- Bleeding ranges from iron-deficiency anemia prising is that in some patients with portal to a life-threatening acute hemorrhage. hypertension, CT detects some pararectal Angiodysplasia is not detected by barium varices not visualized by colonoscopy and enema. Angiography and colonoscopy detect vice versa; the inferior mesenteric vein is only some of these flat lesions. Most angiodys- significantly larger in patients with rectal plasias are intramucosal in location, although varices than in those without. an occasional one is deeper and thus not visible. If bleeding, scintigraphy is an appropriate first Portal Hypertensive Colopathy imaging modality employed. If colonoscopy detects an incidental Vascular ectasia-like lesions in the colon, called angiodysplasia in an otherwise asymptomatic portal hypertensive colopathy, develop in some individual, therapy probably is not necessary. patients with portal hypertension. These lesions Selective mesenteric angiography reveals a consist of numerous irregular vessels having a tuft of abnormal vessels and an early filling vein. hyperemic “cherry-spot” appearance. Superselective arterial embolization is common About one third of patients with severe therapy to arrest acute bleeding from angiodys- cirrhosis have colonic wall thickening, pre- plasias. In some patients, estrogen-progesterone dominantly in the right colon (228); most combination therapy has been successful in patients do not have symptoms referable to the preventing rebleeding from colon, and these changes presumably are related (227). to underlying portal hypertension. Clinically these patients range from asymptomatic, to recurrent rectal bleeding, to episodes of massive Arteriovenous Malformation hemorrhage. Transjugular intrahepatic portosystemic Most arteriovenous malformations are intra- shunting (TIPS) does control bleeding from mural in location.An occasional one has a poly- portal hypertensive colopathy and, in fact, poid appearance. Except for very small ones, the ectasia-like colonic lesions tend to disap- 267

COLON AND RECTUM pear. Colopathy is also corrected after liver node aspirate revealed Histoplasma capsulatum, transplantation and correction of portal but the patient eventually developed bowel hypertension. obstruction and peritonitis. At times Gomori staining of colon biopsies aids in establishing Juvenile Polyps this diagnosis. Patients with AIDS are prone to C. difficile Juvenile polyps persist into adulthood. Occa- infection. Among other predisposing factors in sionally such a juvenile polyp first manifests by this population is the common use of antibi- a massive lower gastrointestinal bleed. otics; clinically, symptoms of C. difficile infec- tion in AIDS patients tend to be more severe Dieulafoy Lesion than in non-AIDS patients. Cytomegalovirus colitis is common in this A small gastric mucosal defect associated with patient population and manifests as ulcers and a bleeding submucosal artery is called a Dieu- submucosal hemorrhage, with these ulcers lafoy lesion (these lesions are discussed in more ranging from aphthous to relatively deep detail in Chapter 2). Since their initial detection cavities surrounded by inflammation and in the stomach, similar lesions have been found edema. These findings are similar to those seen in the small bowel and colon. They appear to be in pseudomembranous colitis. In some, cyto- more common in the proximal colon. They megalovirus infection results in a focal colonic develop in both adults and children. Dieulafoy tumor. Cytomegalovirus is diagnosed by finding lesions occur in diverticula, where their differ- viral inclusion bodies in colon biopsies. These entiation, if any, from a typical diverticular inclusions are more common in cecal biopsies bleed is problematic. rather than more distally; therefore, complete Dieulafoy bleeding is often massive but inter- colonoscopy is necessary. mittent. Similar to gastric Dieulafoy lesions, Similar to other patients, AIDS patients colonoscopic sclerotherapy has successfully develop pseudomembranous colitis when arrested bleeding. Selective mesenteric angiog- treated for an infection. raphy differentiates Dieulafoy lesions from It should be kept in mind that AIDS patients angiodysplasias—the former consists of a small also develop appendicitis. bleeding artery. Neoplasm Immunosuppression (AIDS) Although not common, HIV infection appears to play a role in colorectal cancer development. In patients with human immunodeficiency These patients are at risk for anal squamous and virus infection, superimposed opportunistic cloacogenic carcinomas. infections are common. Yet not all symptoms An occasional rectal Kaposi’s sarcoma is suc- and lesions are due to infection; some are neo- cessfully treated with radiation therapy. plastic and others idiopathic. Complications of non-Hodgkin’s lymphoma in these patients include duodenocolic fistula Infection and intussusception. Colonic histoplasmosis is not uncommon in Other patients with AIDS, with the most common site being the ileocecal region. Clinically, some Some AIDS patients develop pneumatosis coli. patients develop a palpable tumor, and imaging Usually a late finding, in most patients, it is reveals an annular constricting lesion. At times benign and clears spontaneously. The right more diffuse involvement mimics ulcerative colon is involved more often than the left. Occa- colitis. Colonoscopy in one patient revealed sionally pneumatosis coli is associated either volcano-like ulcers and tumors; CT identified with intraperitoneal or retroperitoneal gas and both a colon tumor and hypodense adenopathy suggests a perforation, although bowel perfora- (229); histology and biopsy cultures and lymph tion is not detected. 268

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Prevalence of intussusception is increased in Barium inspissation after a barium enema is patients with AIDS-associated gastrointestinal rare. In most reports it is due to underlying con- disease. Crampy, intermittent abdominal pain is stipation,poor radiographic technique resulting a typical presentation. Either CT or a barium in the overfilling of a dilated, hypotonic colon, enema is diagnostic. or the lack of post-enema hydration. A colitis mimicking ulcerative colitis can develop in an occasional AIDS patient with a low CD4 T-cell count. Colonoscopy Colonoscopic complications consist of bleeding, sepsis, perforation, and transmural burn in- juries, with the onset of symptoms occurring an Examination and average of 30 hours after colonoscopy. Bleeding Surgical Complications is managed conservatively in approximately three quarters of these patients. Barium Enema Disinfection Related A retrospective study of over 700,000 barium enemas performed between 1992 and 1994 in Colonoscopic cleansing is typically achieved the United Kingdom found an overall mortality with glutaraldehyde or hydrogen peroxide. Both rate of one in 56,786 (230); only three of 30 agents produce tissue necrosis. Bloody diarrhea (10%) patients with bowel perforation died, develops within a day or so after these agents compared with nine deaths among 16 (56%) contact colonic mucosa, mimicking ischemic patients with cardiac arrhythmia. One death or infectious colitis. Imaging in patients with was related to vaginal intubation. glutaraldehyde-induced colitis reveals circum- In a setting of incomplete or failed sigmoi- ferential left-sided colonic wall thickening doscopy or colonoscopy, a double-contrast and heterogeneous wall contrast-enhancement; barium enema can be performed the same day these findings resolve on follow-up. Ultrasonog- if no biopsy or only a superficial biopsy (using raphy also identifies colonic wall thickening, small biopsy forceps) is obtained; the risk of consisting of hypoechoic mucosa and hypere- perforation increases if biopsies are taken from choic submucosa. diseased mucosa. A barium enema should be An unusual colitis due to hydrogen peroxide postponed, however, for at least 14 days if a deep developed while colonoscopy was still being biopsy is obtained. A similar delay in perform- performed; it consisted of opaque plaques or ing barium enema also appears warranted if a pseudomembranes, a condition called polypectomy is performed. pseudolipomatosis by pathologists (233). To Focal barium extravasation, either intramural prevent such disinfectant colitis, the authors or extrinsic to bowel, results in an exuberant recommend an additional preprocedure rinse of fibrotic reaction around barium sulfate crystals. colonoscopic channels. An experimental study in rats concluded that any effect of barium sulfate on gastrointestinal Septicemia tract transmural wound healing is minimal (231). At times prior focal extravasation is Approximately 10% of patients develop tran- unsuspected; thus in one patient a tumor in the sient bacteremia after colonoscopy. Septicemia gallbladder fossa was believed to represent an is not common, although the risk of septicemia advanced gallbladder cancer, but resection increases in immunocompromised patients. revealed foreign-body barium granulomas (232). Perforation Venous barium embolization during a barium enema is a rare but highly lethal com- Three mechanisms are associated with plication. Embolization can be either into sys- colonoscopic perforations (234): (1) mechanical temic veins (usually from a rectal perforation) causes due to colonoscopic manipulation, (2) or into portal venous system. barotrauma from overinsufflation, and (3) 269

COLON AND RECTUM perforation related to therapeutic procedures. atherosclerosis results in an inadequate blood In general, perforation occurring during supply to the residual colorectum. diagnostic colonoscopy tends to result in Extraperitoneal emphysema is not uncom- large lacerations; those associated with polypec- mon after a low anterior resection or full- tomy tend to be smaller. Cecal perforations tend thickness excision, raising the question of to be due to overinsufflation; sigmoid perfora- whether it represents benign emphysema or a tions involve mostly technical problems. Some postoperative leak. At times abdominal wall perforations are difficult to understand. Why emphysema develops and persists for a consid- should a jejunal or ileal perforation develop erable time. These entities can usually be dis- after colonoscopy? Some perforations are not tinguished with a contrast enema. Computed diagnosed for several days. tomography findings of a leak consist of gas- The appearance and sequelae of colonic fluid collections adjacent to the rectum and perforation are myriad and are related both extending along tissue planes. With resolution to the extent and site of perforation and of a perforation these collections should gradu- amount of peritoneal soilage. In addition to a ally diminish. pneumoperitoneum, some patients develop Presacral space widening is common after pneumothoraces, pneumopericardium, pneu- rectosigmoid surgery. momediastinum, scrotal swelling, and even subcutaneous emphysema. A tension pneu- Hartmann’s Pouch mothorax can lead to acute respiratory failure. The current trend is toward fewer surgical Based on established surgical indications, either interventions for colonoscopic perforations; a Hartmann’s pouch or a double-barrel some patients with clinically and radiographi- colostomy is created to protect an anastomosis, cally evident perforation heal under medical with surgeons in the United States favoring the management. In fact, medical therapy leads to a former. Complications related to a Hartmann’s shorter hospitalization than with comparable pouch include leaks, strictures, adhesions, and, surgical management. In patients believed to on a more chronic basis, recurrent tumor and require surgery, either primary repair or resec- diversion colitis. A contrast study is often tion and anastomosis are the procedures of requested prior to colostomy takedown, which choice, assuming no contamination is evident. is generally several months or longer after the initial surgery. Occasional debate surfaces Other among radiologists about whether barium or a water-soluble agent should be used; I prefer A number of splenic ruptures have been associ- barium because of its higher contrast and ability ated with colonoscopy. Acute appendicitis to detect more subtle detail, unless the study is developed in a 69-year-old man immediately being performed shortly after resection and the after colonoscopy (235); no signs or symptoms possibility of rupture and intraperitoneal spill of appendicitis were evident prior to are considerations. The presence of barium in a colonoscopy. leak is not an issue—after all, if barium enters a Transient myocardial ischemic episodes sinus tract or cavity, so can infected colonic develop during colonoscopy; these appear to be content, which produces more damage than associated with tachycardia and hypoxemia. inert barium sulfate. A more pertinent issue is that the enema balloon should not be inflated to the same degree as during a normal barium Postresection enema; these patients have decreased rectal Mostly Rectosigmoid Complications pain sensation and, especially with the presence of a stricture, a major rectal perforation can Although colonic ischemia and anastomotic occur. dehiscence is not uncommon after colon Strictures in a Hartmann’s pouch are surgery, rectal ischemia is rare. Rectal necrosis, amenable to transrectal dilation. Most small however, has developed after anterior resection leaks heal with time, although an occasional of a rectosigmoid carcinoma; presumably infe- silent leak is detected by a barium study even rior mesenteric artery ligation in a setting of months later. 270

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Stricture 6. Marshall JB. Brown DN. Photodocumentation of total colonoscopy: how successful are endoscopists? Do Benign postoperative colonic strictures are not reviewers agree? Gastrointest Endosc 1996;44:243–248. uncommon, most being due to ischemia. These 7. Rex DK, Cutler CS, Lemmel GT, et al. Colonoscopic miss rates of adenomas determined by back-to-back strictures are amenable to balloon catheter dila- colonoscopies. 1997;112:24–28. tion, either via colonoscopy or, with distal 8. Cothren RM, Sivak MV Jr, Van Dam J, et al. Detection colonic and rectal strictures, simply using of dysplasia at colonoscopy using laser-induced fluoroscopic control. A preprocedure barium fluorescence: a blinded study. Gastrointest Endosc enema aids in defining the site and length of a 1996;44:168–176. 9. Morrin MM, Farrell RJ, Kruskal JB, Reynolds K, McGee stricture. Procedure complications are rare and JB, Raptopoulos V. Utility of intravenously adminis- stricture recurrence uncommon. tered contrast material at CT colonography. Radiology An occasional ischemic stricture is treated 2000;217:765–771. with a self-expandable metallic prosthesis, but, 10. Fletcher JG, Johnson CD, Welch TJ, et al. Optimization of CT colonography technique: prospective trial in 180 in general, stricture dilation is preferred even in patients. Radiology 2000;216:704–711. high-risk patients. 11. Kulinna C, Scheidler J, Eibel R, et al. [Diagnostic value of different rectal contrast media in the detection of colorectal diseases by multi-slice CT.] [German] Rofo Postlaparoscopy Fortschr Geb Rontgenstr Neuen Bildgeb Verfahr 2002;173:749–755. Laparoscopic resections of sigmoid diverticuli- 12. Morrin MM, Kruskal JB, Farrell RJ, Goldberg SN, McGee JB, Raptopoulos V.Endoluminal CT colonogra- tis leads to a severalfold increase in operative phy after an incomplete endoscopic colonoscopy. AJR time over open resection but a decrease in 1999;172:913–918. intensive care. Length of hospital stay, compli- 13. Pickhardt PJ. Translucency rendering in 3D endolumi- cations, and operating time decrease with nal CT colonography: a useful tool for increasing polyp experience. specificity and decreasing interpretation time. AJR 2004;183:429–436. Abdominal wall tumor recurrence at a trocar- 14. McFarland EG, Brink JA, Pilgram TK, et al. Spiral CT site scar does occur after laparoscopic carci- colonography: reader agreement and diagnostic per- noma resection. This complication is rare in a formance with two- and three-dimensional image- laparotomy scar. display techniques. Radiology 2001;218:375–383. 15. Macari M, Milano A, Lavelle M, Berman P,Megibow AJ. Port site hernias are an uncommon compli- Comparison of time-efficient CT colonography with cation of laparoscopic colectomy. Superior two- and three-dimensional colonic evaluation for mesenteric and portal vein thrombosis detecting colorectal polyps. AJR 2000;174:1543– occurred after a laparoscopically assisted right 1549. hemicolectomy. 16. Sosna J, Morrin MM, Kruskal JB, Lavin PT, Rosen MP, Raptopoulos V. CT colonography of colorectal polyps: a metaanalysis. AJR 2003;181:1593–1598. 17. Callstrom MR, Johnson CD, Fletcher JG, et al. Com- puted tomography colonography without cathartic References preparation: feasibility study. Radiology 2001;219: 693–698. 1. Langdon DE. Radiologic barium and colon toxicity. 18. Summers RM, Johnson CD, Pusanik LM, Malley JD, Am J Gastroenterol 1994;89:462. Youssef AM, Reed JE.Automated polyp detection at CT 2. Harvey CJ, Halligan S, Bartram CI, Hollings N, Sahdev colonography: feasibility assessment in a human pop- A, Kingston K. Evacuation proctography: a prospective ulation. Radiology 2001;219:51–59. study of diagnostic and therapeutic effects. Radiology 19. Luboldt W, Mann C, Tryon CL, et al. Computer-aided 1999;211:223–227. diagnosis in contrast-enhanced CT colonography: an 3. Schoenenberger AW, Debatin JF, Guldenschuh I, Hany approach based on contrast. Eur Radiol 2002;12:2236– TF, Steiner P, Krestin GP. Dynamic MR defecography 2241. with a superconducting, open-configuration MR 20. Zalis ME, Hahn PF, Arellano RS, Gazelle GS, Mueller system. Radiology 1998;206:641–646. PR. CT colonography with teleradiology: effect of lossy 4. Paetzel C, Strotzer M, Furst A, Rentsch M, Lenhart M, wavelet compression on polyp detection—initial Feuerbach S. [Dynamic MR defecography for diagno- observations. Radiology 2001;220:387–392. sis of combined functional disorders of the pelvic floor 21. Hara AK, Johnson CD, MacCarty RL, Welch TJ. Inci- in proctology.] [German] Rofo Fortschr Geb Rontgen- dental extracolonic findings at CT colonography. Radi- str Neuen Bildgeb Verfahr 2001;173:410–415. ology 2000;215:353–357. 5. Maier A, Fuchsjager M, Funovics M. [Endoanal mag- 22. Luboldt W, Bauerfeind P, Wildermuth S, Marincek B, netic resonance tomography in fecal incontinence.] Fried M, Debatin JF. Colonic masses: detection with [Review] [German] Radiologe 2000;40:465–468. MR colonography. Radiology 2000;216:383–388. 271

COLON AND RECTUM

23. Luboldt W, Frohlich JM, Schneider N, Weishaupt D, between ulcerative colitis and Crohn’s disease. Korean Landolt F, Debatin JF. MR colonography: optimized J Intern Med 1997;12:7–15. enema composition. Radiology 1999;212:265–269. 41. Okada M, Maeda K, Yao T, et al. Right-sided ulcerative 24. Luboldt W,Luz O,Vonthein R, et al. Three-dimensional colitis. [Review] J Gastroenterol 1996;31:717–722. double-contrast MR colonography: a display method 42. Cammarota T, Bresso F, Sarno A, Astegiano M, simulating double-contrast barium enema. AJR Macchiarella V,Robotti D. [Abdominal pain and bowel 2001;176:930–932. dysfunction: the diagnostic role of ultrasonography.] 25. Chung JJ, Semelka RC, Martin DR, Marcos HB. Colon [Italian] Radiol Med 2000;100:337–342. diseases: MR evaluation using combined T2–weighted 43. Schunk K, Reiter S, Kern A, Orth T, Wanitschke R. single-shot echo train spin-echo and gadolinium- [Hydro-MRI in inflammatory bowel diseases: a com- enhanced spoiled gradient-echo sequences. J Magn parison with colonoscopy and histology.] [German] Reson Imaging 2000;12:297–305. Rofo Fortschr Geb Rontgenstr Neuen Bildgeb Verfahr 26. Lomas DJ, Sood RR, Graves MJ, Miller R, Hall NR, 2001;173:731–738. Dixon AK. Colon carcinoma: MR imaging with CO2 44. Charron M, del Rosario FJ, Kocoshis SA. Pediatric enema—pilot study. Radiology 2001;219:558–562. inflammatory bowel disease: assessment with scintig- 27. Lauenstein T, Holtmann G, Schoenfelder D, Bosk S, raphy with 99mTc white blood cells. Radiology 1999; Ruehm SG, Debatin JF. MR colonography without 212:507–513. colonic cleansing: a new strategy to improve patient 45. Lapidus A, Bernell O, Hellers G, Lofberg R. Clinical acceptance. AJR 2001;177:823–827. course of colorectal Crohn’s disease: a 35–year follow- 28. Locher C, Duclos-Vallee JC, Rocher L, Blery M, Buffet up study of 507 patients. Gastroenterology 1998;114: C. [Bilateral Chilaiditi’s syndrome.] [French] Presse 1151–1160. Med 2000;29:1738. 46. Nordenholtz KE, Stowe SP, Stormont JM, et al. The 29. Pinto A, Brunese L, Noviello D, Catalano O. [Colonic cause of death in inflammatory bowel disease: a com- interposition between kidney and psoas muscle: parison of death certificates and hospital charts in anatomical variation studied with CT.] [Italian] Radiol Rochester, New York. Am J Gastroenterol 1995;90: Med 1997;94:58–60. 927–932. 30. Prassopoulos P, Raissaki M, Daskalogiannaki M, 47. Schunk K, Kern A, Heussel CP,et al. [Hydro-MRT with Gourtsoyiannis N. Retropsoas positioned bowel: inci- fast sequences in Crohn’s disease: a comparison with dence and clinical relevance. J Comput Assist Tomogr fractionated gastrointestinal passage.] [German] Rofo 1998;22:304–307. Fortschr Geb Rontgenstr Neuen Bildgeb Verfahr 31. Currarino G, Coln D, Votteler T. Triad of anorectal, 1999;170:338–346. sacral, and presacral anomalies. AJR 1981;137:395– 48. Ferguson A.Assessment and management of ulcerative 398. colitis in children. [Review] Eur J Gastroenterol 32. Lee SC, Chun YS, Jung SE, Park KW, Kim WK. Cur- Hepatol 1997;9:858–863. rarino triad: anorectal malformation, sacral bony 49. Raithel M, Winterkamp S, Pacurar A, Ulrich P, abnormality, and presacral mass—a review of 11 cases. Hochberger J, Hahn EG. Release of mast cell tryptase J Pediatr Surg 1997;32:58–61. from human colorectal mucosa in inflammatory bowel 33. Vidiscak M, Kirnak J, Smrek M. [Results of surgery in disease. Scand J Gastroenterol 2001;36:174–179. children with congenital megacolon.] [Slovak] Rozhl 50. Orholm M, Binder V,Sorensen TI, Rasmussen LP,Kyvik Chir 2001;80:197–200. KO. Concordance of inflammatory bowel disease 34. Bloom DA, Buonomo C, Fishman SJ, Furuta G, Nurko among Danish twins. Results of a nationwide study. S. Allergic colitis: a mimic of Hirschsprung disease. Scand J Gastroenterol 2000;35:1075–1081. Pediatr Radiol 1999;29:37–41. 51. Tzivras M, Souyioultzis S, Tsirantonaki M, Archiman- 35. Benya EC, Nussbaum-Blask AR, Selby DM. Colonic dritis A. Chronic granulocytic leukemia in a patient diverticulitis causing partial bowel obstruction in a with ankylosing spondylitis and ulcerative colitis: an child with cystic fibrosis. Pediatr Radiol 1997;27: interesting association. [Review] J Clin Gastroenterol 918–919. 1997;25:365–366. 36. Binkovitz LA, Allen E, Bloom D, et al. Atypical presen- 52. Maconi G, Ardizzone S, Parente F, Bianchi Porro G. tation of Clostridium difficile colitis in patients with Ultrasonography in the evaluation of extension, activ- cystic fibrosis. AJR 1999;172:517–521. ity, and follow-up of ulcerative colitis. Scand J Gas- 37. Bru C, Sans M, Defelitto MM, et al. Hydrocolonic troenterol 1999;34:1103–1110. sonography for evaluating inflammatory bowel 53. Mirk P, Palazzoni G, Gimondo P. Doppler sonography disease. AJR 2001;177:99–105. of hemodynamic changes of the inferior mesenteric 38. Lee BF,Chiu NT,Wu DC, et al. Use of 99mTc (V) DMSA artery in inflammatory bowel disease: preliminary scintigraphy in the detection and localization of intes- data. AJR 1999;173:381–387. tinal inflammation: comparison of findings and 54. Guslandi M, Sorghi S, Polli D, Tittobello A. Measure- colonoscopy and biopsy. Radiology 2001;220:381– ment of rectal blood flow by laser Doppler flowmetry 385. in inflammatory bowel disease. Hepatogastroenterol- 39. Halme L, Edgren J, Turpeinen U, von Smitten K, ogy 1998;45:445–446. Stenman UH. Urinary excretion of iohexol as a marker 55. Yamamoto T, Keighley MR. Proctocolectomy is associ- of disease activity in patients with inflammatory bowel ated with a higher complication rate but carries a lower disease. Scand J Gastroenterol 1997;32:148–152. recurrence rate than total colectomy and ileorectal 40. Lee HB, Kim JH,Yim CY,Kim DG, Ahn DS. Differences anastomosis in Crohn colitis. Scand J Gastroenterol in immunophenotyping of mucosal lymphocytes 1999;34:1212–1215. 272

ADVANCED IMAGING OF THE ABDOMEN

56. Yamamoto T, Keighley MR. Long-term outcome of 75. Pardi DS, Tremaine WJ, Rothenberg HJ, Batts KP. total colectomy and ileostomy for Crohn disease. Melanosis coli in inflammatory bowel disease. J Clin Scand J Gastroenterol 1999;34:280–286. Gastroenterol 1998;26:167–170. 57. Garcia Picazo D, Bermudez Rodriguez E, Moreno 76. Nusko G, Schneider B, Schneider I, Wittekind C, Hahn Resina JM. Acute cholecystitis after colectomy for EG. Anthranoid laxative use is not a risk factor for ulcerative colitis. Rev Esp Enferm Dig 2000;92:392– colorectal neoplasia: results of a prospective case 398. control study. Gut 2000;46:651–655. 58. Schmidt CM, Horton KM, Sitzmann JV,Jones B, Bayless 77. Tomas ME, Casis B, Soto S, et al. [Salmonella T. Simple radiographic evaluation of ileoanal pouch osteomyelitis in a patient with collagenous colitis.] volume. Dis Colon Rectum 1996;39:66–73. [Spanish] Rev Esp Enferm Dig 1999;91:76–77. 59. Aitola P, Matikainen M, Mattila J, Tomminen T, 78. De La Riva S, Betes MT, Duque JM, Angos R, Munoz Hiltunen KM. Chronic inflammatory changes in the Navas MA.Collagenous colitis and lymphocytic colitis: pouch mucosa are associated with cholangitis found clinical and endoscopic findings. Rev Esp Enferm Dig on perioperative liver biopsy specimens at restorative 2000;92:86–96. proctocolectomy for ulcerative colitis. Scand J Gas- 79. Bellin MF, Darchen MA, Hoang C, et al. Rectal mala- troenterol 1998;33:289–293. coplakia in renal transplantation: MR features. J 60. Libicher M, Scharf J, Wunsch A, Stern J, Dux M, Comput Assist Tomogr 1994;18:975–978. Kauffmann GW.MRI of pouch-related fistulas in ulcer- 80. Molik KA, West KW, Rescorla FJ, Scherer LR, Engum ative colitis after restorative proctocolectomy. J SA, Grosfeld JL. Portal venous air: the poor prognosis Comput Assist Tomogr 1998;22:664–668. persists. J Pediatr Surg 2001;36:1143–1145. 61. Wong SK, Ho YH, Leong AP, Seow-Choen F. Clinical 81. Patton WL, Willmann JK, Lutz AM, Rencken IO, behavior of complicated right-sided and left-sided Gooding CA. Worsening enterocolitis in neonates: diverticulosis. Dis Colon Rectum 1997;40:344–348. diagnosis by CT examination of urine after enteral 62. Chintapalli KN, Chopra S, Ghiatas AA, Esola CC, Fields administration of iohexol. Pediatr Radiol 1999;29: SF, Dodd GD 3rd. Diverticulitis versus colon cancer: 95–99. differentiation with helical CT findings. Radiology 82. Balthazar EJ, Yen BC, Gordon RB. Ischemic colitis: CT 1999;210:429–435. evaluation of 54 cases. Radiology 1999;211:381–388. 63. Rao PM, Rhea JT. Colonic diverticulitis: evaluation of 83. Millward SF, Fortier M. Transient gastric emphysema the arrowhead sign and the inflamed diverticulum for caused by colonic infarction. AJR 2001;176:1331– CT diagnosis. Radiology 1998;209:775–779. 1332. 64. Jang HJ, Lim HK, Lee SJ, Lee WJ, Kim EY,Kim SH.Acute 84. Danse EM, Van Beers BE, Jamart J, et al. Prognosis of diverticulitis of the cecum and ascending colon: the ischemic colitis: comparison of color Doppler sonog- value of thin-section helical CT findings in excluding raphy with early clinical and laboratory findings. AJR colonic carcinoma. AJR 2000;174:1397–1402. 2000;175:1151–1154. 65. Blakeborough A, Chapman AH, Swift S, Culpan G, 85. Yao T, Iwashita A, Hoashi T, et al. Phlebosclerotic Wilson D, Sheridan MB. Strictures of the sigmoid colitis: value of radiography in diagnosis—report of colon: barium enema evaluation. Radiology three cases. Radiology 2000;214:188–192. 2001;220:343–348. 86. Shiojima K, Mitsuhashi N, Yamakawa M, Sakurai H, 66. Miller FH, Ma JJ, Scholz FJ. Imaging features of entero- Niibe H. Transrectal ultrasonography in evaluation of hemorrhagic Escherichia coli colitis. AJR 2001;177: chronic rectal complications after radiation therapy 619–623. for carcinoma of the uterine cervix. Invest Radiol 67. Satoh T, Sasatomi E, Wu L, Tokunaga O. Phlegmonous 1998;33:74–79. colitis: a specific and severe complication of chronic 87. Chen JH, Lai SJ, Tsai PP, Chen YF. Localized amyloido- hepatic disease. Virchows Arch 2000;437:656–661. sis mimicking carcinoma of the colon. AJR 2002; 68. Takahashi T, Gamboa-Dominguez A, Gomez-Mendez 179:536–537. TJ, et al. Fulminant amebic colitis: analysis of 55 cases. 88. Boudiaf M, Zidi SH, Soyer P, et al. [Primary epiploic Dis Colon Rectum 1997;40:1362–1367. appendicitis: CT diagnosis for conservative treat- 69. Sachdev GK, Dhol P. Colonic involvement in patients ment.] [French] Presse Med 2000;29:231–236. with amebic liver abscess: endoscopic findings. Gas- 89. Takada A, Moriya Y, Muramatsu Y, Sagae T. A case of trointest Endosc 1997;46:37–39. giant peritoneal loose bodies mimicking calcified 70. Nagi B, Kochhar R, Bhasin DK, Singh K. Colorectal leiomyoma originating from the rectum. Jpn J Clin tuberculosis. [Review] Eur Radiol 2003;13:1907–1912. Oncol 1998;28:441–442. 71. Lee IJ, Ha HK, Park CM, et al. Abdominopelvic actino- 90. Croizet O, Moreau J, Arany Y, Delvaux M, Rumeau JL, mycosis involving the gastrointestinal tract: CT fea- Escourrou J. Follow-up of patients with hyperplastic tures. Radiology 2001;220:76–80. polyps of the large bowel. Gastrointest Endosc 72. Uchiyama N, Ishikawa T, Miyakawa K, et al. Abdomi- 1997;46:119–123. nal actinomycosis: barium enema and computed 91. Cunnane ME, Rubesin SE, Furth EE, Levine MS, Laufer tomography findings. J Gastroenterol 1997;32:89–94. I. Small flat umbilicated tumors of the colon: radi- 73. Kirkpatrick ID, Greenberg HM. Evaluating the CT ographic and pathologic findings. AJR 2000;175: diagnosis of Clostridium difficile colitis: should CT 747–749. guide therapy? AJR 2001;176:635–639. 92. Baldisserotto M, Spolidoro JV, Bahu Mda G. Graded 74. Benoit R, Grobost O, Crepeau T.[Diaphragm-like stric- compression sonography of the colon in the diagnosis tures of the colon from diclofenac.] [Review] [French] of polyps in pediatric patients. AJR 2002;179:201– Presse Med 2001;30:1102–1104. 205. 273

COLON AND RECTUM

93. Chiba M, Yamano H, Fujiwara K, Abe T, Iizuka M, the context of a syndrome of hereditary predisposition Watanabe S. Lymph folliculitis in ulcerative colitis. to HNPCC colonic cancer.] [French] Prog Urol Scand J Gastroenterol 2001;36:332–336. 2000;10:1204–1207. 94. Fedele L, Bianchi S, Portuese A, Borruto F, Dorta M. 111. Gafa R, Lanza G. [Expression of protein p53 in the Transrectal ultrasonography in the assessment of rec- adenoma-colorectal carcinoma sequence.][Italian] tovaginal endometriosis. Obstet Gynecol 1998;91: Pathologica 1998;90:351–356. 444–448. 112. Vasen HF, Sanders EA, Taal BG, et al. The risk of brain 95. Manfredi R,Valentini AL. Magnetic resonance imaging tumours in hereditary non-polyposis colorectal cancer of pelvic endometriosis. Rays 1998;23:702–708. (HNPCC). Int J Cancer 1996;65:422–425. 96. Smith TR, Fine SW, Jones JG. CT appearance of some 113. Bertario L, Russo A, Sala P, et al. Risk of colorectal colonic villous tumors. AJR 2001;177:91–93. cancer following colonoscopic polypectomy. Tumori 97. Whitelaw SC, Murday VA, Tomlinson IP, et al. Clinical 1999;85:157–162. and molecular features of the hereditary mixed 114. Passman MA, Pommier RF, Vetto JT. Synchronous polyposis syndrome. Gastroenterology 1997;112:327– colon primaries have the same prognosis as solitary 334. colon cancers. [Review] Dis Colon Rectum 1996;39: 98. Bjork J, Akerbrant H, Iselius L, Alm T, Hultcrantz R. 329–334. Epidemiology of familial adenomatous polyposis in 115. Conde P,Erdozain JC, Olveira A, Herrera A, Segura JM. Sweden: changes over time and differences in pheno- [A patient with five synchronous adenocarcinomas of type between males and females. Scand J Gastroenterol the colon.] [Spanish] Rev Esp Enferm Dig 1998;90: 1999;34:1230–1235. 124. 99. Debinski HS, Love S, Spigelman AD, Phillips RK. 116. Shida H, Ban K, Matsumoto M, et al. Asymptomatic Colorectal polyp counts and cancer risk in familial colorectal cancer detected by screening. Dis Colon adenomatous polyposis. Gastroenterology 1996;110: Rectum 1996;39:1130–1135. 1028–1030. 117. Macari M, Bini EJ, Jacobs SL, et al. Significance of 100. Svab J, Peskova M, Jirasek V, Fried M, Krska Z. [Long- missed polyps at CT colonography. AJR 2004; term results of ileo-rectal anastomosis in familial poly- 183:127–134. posis.] [Czech] Rozhl Chir 1999;78:150–153. 118. Nusko G, Mansmann U, Partzsch U, et al. Invasive car- 101. Parc YR, Olschwang S, Desaint B, Schmitt G, Parc RG, cinoma in colorectal adenomas: multivariate analysis Tiret E. Familial adenomatous polyposis: prevalence of of patient and adenoma characteristics. Endoscopy adenomas in the ileal pouch after restorative procto- 1997;29:626–631. colectomy. Ann Surg 2001;233:360–364. 119. Ueyama T, Kawamoto K, Iwashita I, et al. Natural 102. Belchetz LA, Berk T, Bapat BV, Cohen Z, Gallinger S. history of minute sessile colonic adenomas based on Changing causes of mortality in patients with familial radiographic findings. Is endoscopic removal of every adenomatous polyposis. Dis Colon Rectum 1996;39: colonic adenoma necessary? Dis Colon Rectum 384–387. 1995;38:268–272. 103. Suzui M, Yoshimi N, Hara A, Morishita Y, Tanaka T, 120. Tarraga P, Garcia-Olmo D, Celada A, Garcia-Molinero Mori H. Genetic alterations in a patient with Turcot’s Mf, Divison JA, Casado C. Colorectal cancer screening syndrome. Pathol Int 1998;48:126–133. through detection of fecal occult blood in a controlled 104. Marsh DJ, Coulon V, Lunetta K, et al. Mutation spec- health zone. Rev Esp Enferm Dig 1999;91:335–344. trum and genotype-phenotype analyses in Cowden 121. Frazier AL, Colditz GA, Fuchs CS, Kuntz KM. Cost- disease and Bannayan-Zonana syndrome, two hamar- effectiveness of screening for colorectal cancer in the toma syndromes with germline PTEN mutation. Hum general population. JAMA 2000;284:1954–1961. Mol Genet 1998;7:507–515. 122. Pariente A, Milan C, Lafon J, Faivre J. Colonoscopic 105. Cho KC, Sundaram K, Sebastiano LS. Filiform polypo- screening in first-degree relatives of patients with sis of the small bowel in a patient with multiple hamar- ‘sporadic’ colorectal cancer: a case-control study. The toma syndrome (Cowden disease). AJR 1999;173: Association Nationale des Gastroenterologues des 501–502. Hopitaux and Registre Bourguignon des Cancers 106. Wada K, Asoh T, Imamura T, et al. Rectal carcinoid Digestifs (INSERM CRI 9505). Gastroenterology tumor associated with the Peutz-Jeghers syndrome. 1998;115:7–12. J Gastroenterol 1998;33:743–746. 123. McMahon PM, Bosch JL, Gleason S, Halpern EF, Lester 107. Parnaud G, Corpet DE. [Colorectal cancer: controver- JS, Gazelle GS. Cost-effectiveness of colorectal cancer sial role of meat consumption.] [Review] [French] Bull screening. Radiology 2001;219:44–50. Cancer 1997;84:899–911. 124. Okamura S, Ohashi S, Mitake M, et al. [A case of minute 108. Potter MA, Cunliffe NA, Smith M, Miles RS, Flapan AD, IIa + IIc type early colonic cancer (5mm in size and Dunlop MG. A prospective controlled study of the sm 1 in invasion depth) with metachronous liver association of Streptococcus bovis with colorectal car- metastasis.] [Japanese] Nippon Shokakibyo Gakkai cinoma. J Clin Pathol 1998;51:473–474. Zasshi 1998;95:890–894. 109. Toyoki Y, Satoh S, Morioka G, Asano M, Nomura 125. Garcia-Hirschfeld Garcia J, Blanes Berenguel A, K. Rectal cancer associated with acquired hyper- Vicioso Recio L, Marquez Moreno A, Rubio Garrido J, trichosis lanuginosa as a possible cutaneous marker Matilla Vicente A. Colon cancer: p53 expression and of internal malignancy. J Gastroenterol 1998;33: DNA ploidy. Their relation to proximal or distal tumor 575–577. site. Rev Esp Enferm Dig 1999;91:481–488. 110. de la Taille A, Mariette C, Buisine MP, Biserte J, 126. Rex DK, Rahmani EY,Haseman JH, Lemmel GT, Kaster Triboulet JP. [Urothelial tumor and colonic cancer in S, Buckley JS. Relative sensitivity of colonoscopy and 274

ADVANCED IMAGING OF THE ABDOMEN

barium enema for detection of colorectal cancer in 143. Alcobendas F, Jorba R, Poves I, Busquets J, Engel A, clinical practice. Gastroenterology 1997;112:17–23. Jaurrieta E. Perforated colonic cancer. Evolution and 127. Strom E, Larsen JL. Colon cancer at barium enema prognosis. Rev Esp Enferm Dig 2000;92:326–333. examination and colonoscopy: a study from the county 144. Galia M, Midiri M, Carcione A, et al. [Usefulness of CT of Hordaland, Norway. Radiology 1999;211:211–214. colonography in the preoperative evaluation of 128. Hancock JH, Talbot RW. Accuracy of colonoscopy in patients with distal occlusive colorectal carcinoma.] localisation of colorectal cancer. Int J Colorectal Dis [Italian] Radiol Med 2001;101:235–242. 1995;10:140–141. 145. Fenlon HM, McAneny DB, Nunes DP, Clarke PD, 129. Haseman JH, Lemmel GT,Rahmani EY,Rex DK. Failure Ferrucci JT. Occlusive colon carcinoma: virtual of colonoscopy to detect colorectal cancer: evaluation colonoscopy in the preoperative evaluation of the of 47 cases in 20 hospitals. Gastrointest Endosc proximal colon. Radiology 1999;210:423–428. 1997;45:451–455. 146. Camunez F, Echenagusia A, Simo G, Turegano F, 130. Jang HJ, Lim HK, Park CK, Kim SH, Park JM, Choi YL. Vazquez J, Barreiro-Meiro I. Malignant colorectal Segmental wall thickening in the colonic loop distal to treated by means of self-expanding metallic stents: colonic carcinoma at CT: importance and histopatho- effectiveness before surgery and in palliation. Radiol- logic correlation. Radiology 2000;216:712–717. ogy 2000;216:492–497. 131. Oto A, Gelebek V, Oguz BS, et al. CT attenuation of 147. Mainar A, De Gregorio Ariza MA, Tejero E, et al. colorectal polypoid lesions: evaluation of contrast Acute colorectal obstruction: treatment with self- enhancement in CT colonography. Eur Radiol 2003; expandable metallic stents before scheduled surgery— 13:1657–1663. results of a multicenter study. Radiology 1999;210: 132. Morrin MM, Farrell RJ, Kruskal JB, Reynolds K, McGee 65–69. JB, Raptopoulos V. Utility of intravenously adminis- 148. Falchi M, Cecchini G, Derchi LE. [Umbilical metastasis tered contrast material at CT colonography. Radiology as first sign of cecal carcinoma in a cirrhotic patient 2000;217:765–771. (Sister Mary Joseph nodule).Report of a case.] [Italian] 133. Yee J, McFarland E. How accurate is CT colonography? Radiol Med 1999;98:94–96. In: Dachman AH,ed.Atlas of Virtual Colonoscopy.New 149. Osin P, Shiloni E, Pikarsky AJ, Okon E. Metastatic York: Springer, 2003:11–16. adenocarcinoma in a thyroid colloid nodule: a rare 134. Morra A, Meduri S, Ammar L, Ukmar M, Pozzi Mucelli presentation of colon cancer. Pathology 1996;28: R. [Colonoscopy with computed tomography with 236–237. volume reconstruction. The results and a comparison 150. Sefr R, Penka I, Oliva T.[Carcinoma of the colon invad- with endoscopy and surgery.] [Italian] Radiol Med ing the duodenum and pancreas.] [Czech] Rozhl Chir 1999;98:162–167. 2000;79:112–115. 135. Regge D, Galatola G, Martincich L, et al. [Use of virtual 151. Zerhouni EA, Rutter C, Hamilton SR, et al. CT and MR endoscopy with computerized tomography in the imaging in the staging of colorectal carcinoma: report identification of colorectal neoplasms. Prospective of the Radiology Diagnostic Oncology Group II. Radi- study with symptomatic patients.] [Italian] Radiol ology 1996;200:443–451. Med 2000;99:449–455. 152. Sitzler PJ, Seow-Choen F, Ho YH, Leong AP. Lymph 136. Yee J, Akerkar GA, Hung RK, Steinauer-Gebauer AM, node involvement and tumor depth in rectal cancers: Wall SD, McQuaid KR. Colorectal neoplasia: perform- an analysis of 805 patients. Dis Colon Rectum ance characteristics of CT colonography for detection 1997;40:1472–1476. in 300 patients. Radiology 2001;219:685–692. 153. Bipat S, Glas AS, Slors FJ, Zwinderman AH, Bossuyt 137. Galdino GM, Yee J. Carpet lesion on CT colonography: PM, Stoker J. Rectal cancer: local staging and assess- a potential pitfall. AJR 2003;180:1332–1334. ment of lymph node involvement with endoluminal 138. Matsui T, Yao T, Yao K, et al. Natural history of US, CT, and MR imaging—a meta-analysis. Radiology superficial depressed colorectal cancer: retrospective 2004;232:773–783. radiographic and histologic analysis. Radiology 154. Civelli EM, Gallino G, Mariani L, et al. Double-contrast 1996;201:226–232. barium enema and computerised tomography in the 139. Sada M, Mitomi H, Igarashi M, Katsumata T, Saigenji pre-operative evaluation of rectal carcinoma: are they K, Okayasu I. Cell kinetics, p53 and bcl-2 expression, still useful diagnostic procedures? Tumori 2000;86: and c-Ki-ras mutations in flat-elevated tubulovillous 389–392. adenomas and adenocarcinomas of the colorectum: 155. Palko A, Gyulai C, Fedinecz N, Balogh A, Nagy F.Water comparison with polypoid lesions. Scand J Gastroen- enema CT examination of rectum cancer by reduced terol 1999;34:798–807. amount of water. Rofo Fortschr Geb Rontgenstr Neuen 140. Rubio CA, Kumagai J, Kanamori T, Yanagisawa A, Bildgeb Verfahr 2000;172:901–904. Nakamura K, Kato Y. Flat adenomas and flat adeno- 156. Fuchsjager MH, Maier AG, Schima W, et al. Compari- carcinomas of the colorectal mucosa in Japanese and son of transrectal sonography and double-contrast MR Swedish patients. Comparative histologic study. Dis imaging when staging rectal cancer. AJR 2003;181: Colon Rectum 1995;38:1075–1079. 421–427. 141. Watari J, Saitoh Y, Obara T, et al. Early nonpolypoid 157. Lindmark GE, Kraaz WG, Elvin PA, Glimelius BL. colorectal cancer: radiographic diagnosis of depth of Rectal cancer: evaluation of staging with endosonog- invasion. Radiology 1997;205:67–74. raphy. Radiology 1997;204:533–538. 142. Kao PF, Tzen KY, Chang PL, Chang-Chien CR, Tsai MF, 158. Kruskal JB, Sentovich SM, Kane RA. Staging of rectal You DL. Diuretic renography findings in enterovesical cancer after polypectomy: usefulness of endorectal US. fistula. Br J Radiol 1997;70:421–423. Radiology 1999;211:31–35. 275

COLON AND RECTUM

159. Wallengren NO, Holtas S,Andren-Sandberg A, Jonsson washing in colon cancer. Scand J Gastroenterol E, Kristoffersson DT, McGill S. Rectal carcinoma: 1999;34:606–610. double-contrast MR imaging for preoperative staging. 174. Stuckle CA, Maleszka A, Kosta P, Kirchner JK, Radiology 2000;215:108–114. Liermann D,Adamietz IA. [Computerized tomography 160. Maier AG, Kersting-Sommerhoff B, Reeders JW, et al. evaluation of local recurrence of operated and adju- Staging of rectal cancer by double-contrast MR vant radiation treated rectal carcinoma. Normal and imaging using the rectally administered super- pathological changes after operation and irradiation of paramagnetic iron oxide contrast agent ferristene and rectal carcinoma in 956 CT examinations.] [German] IV gadodiamide injection: results of a multicenter Radiologe 2001;41:491–496. phase II trial. J Magn Reson Imaging 2000;12:651– 175. Even-Sapir E, Parag Y, Lerman H, et al. Detection of 660. recurrence in patients with rectal cancer: PET/CT after 161. Koh D-M, Brown G, Temple L, et al. Rectal Cancer: abdominoperineal or anterior resection. Radiology Mesorectal Lymph Nodes at MR Imaging with USPIO 2004;232:815–822. versus Histopathologic Findings-Initial Observations. 176. Kinkel K, Tardivon AA, Soyer P, et al. Dynamic con- Radiology 2004;231:91–99. trast-enhanced subtraction versus T2–weighted spin- 162. Urban M, Rosen HR, Holbling N, et al. MR imaging for echo MR imaging in the follow-up of colorectal the preoperative planning of sphincter-saving surgery neoplasm: a prospective study of 41 patients. Radiol- for tumors of the lower third of the rectum: use of ogy 1996;200:453–458. intravenous and endorectal contrast materials. Radiol- 177. Abu-Rustum N, Barakat RR, Curtin JP. Ovarian and ogy 2000;214:503–508. uterine disease in women with colorectal cancer. 163. Hussain SM, Outwater EK, Siegelman ES. Mucinous Obstet Gynecol 1997;89:85–87. versus nonmucinous rectal carcinomas: differentiation 178. Philpott GW, Schwarz SW, Anderson CJ, et al. with MR imaging. Radiology 1999;213:79–85. Radioimmuno-PET- detection of colorectal carcinoma 164. Filippone A, Ambrosini R, Fuschi M, Marinelli T, with positron-emitting copper-64–labeled monoclonal Genovesi D, Bonomo L. Preoperative T and N Staging antibody. J Nucl Med 1995;36:1818–1824. of Colorectal Cancer: Accuracy of Contrast-enhanced 179. Olofinlade O, Adeonigbagbe O, Gualtieri N, et al. Anal Multi-Detector Row CT Colonography-Initial Experi- carcinoma: a 15–year retrospective analysis. Scand J ence. Radiology 2004;231:83–90. Gastroenterol 2000;35:1194–1199. 165. Abdel-Nabi H, Doerr RJ, Lamonica DM, et al. Staging 180. Lee HJ, Han JK, Kim TK, Kim YH, Kim KW, Choi BI. of primary colorectal carcinomas with fluorine-18 Peripheral T-cell lymphoma of the colon: double- fluorodeoxyglucose whole-body PET: correlation with contrast barium enema examination findings in six histopathologic and CT findings. Radiology patients. Radiology 2001;218:751–756. 1998;206:755–760. 181. Kim KW, Ha HK, Kim AY, et al. Primary malignant 166. Paule B, Brion N. [Metastatic colorectal cancer: new melanoma of the rectum: CT findings in eight patients. therapeutics.] [Review] [French] Presse Med Radiology 2004;232:181–186. 2000;29:1072–1077. 182. Krestin GP, Hauser M, Eichenberger A, Kochli 167. de Vries A, Griebel J, Kremser C, et al. Monitoring of OR. [Bladder and rectal infiltration by uterine carci- tumor microcirculation during fractionated radiation nomas: the accuracy of CT and MRI compared to therapy in patients with rectal carcinoma: preliminary endoscopic procedures.] [German] Rofo Fortschr results and implications for therapy. Radiology Geb Rontgenstr Neuen Bildgeb Verfahr 1997;167: 2000;217:385–391. 125–131. 168. Delaloye AB, Delaloye B, Buchegger F, et al. Compari- 183. Ha HK, Jee KR, Yu E, et al. CT features of metastatic son of copper-67– and iodine-125–labeled anti-CEA linitis plastica to the rectum in patients with peritoneal monoclonal antibody biodistribution in patients with carcinomatosis. AJR 2000;174:463–466. colorectal tumors. J Nucl Med 1997;38:847–853. 184. Miyayama S, Matsui O, Kifune K, et al. Malignant 169. De Santis M, Ariosi P, Calo GF, Luppi G, Franchini M, colonic obstruction due to extrinsic tumor: palliative Romagnoli R. [Antineoplastic perfusion with percuta- treatment with a self-expanding nitinol stent. AJR neous stop-flow control in the treatment of advanced 2000;175:1631–1637. pelvic malignant neoplasms.] [Italian] Radiol Med 185. Soga J. Carcinoids of the colon and ileocecal region: 2000;100:56–61. a statistical evaluation of 363 cases collected from 170. de Gregorio MA, Mainar A, Tejero E, et al. Acute the literature. J Exp Clin Cancer Res 1998;17:139– colorectal obstruction: stent placement for palliative 148. treatment—results of a multicenter study. Radiology 186. Spread C, Berkel H, Jewell L, Jenkins H, Yakimets W. 1998;209:117–220. Colon carcinoid tumors.A population-based study. Dis 171. Laghi A, Iannaccone R, Bria E, et al. Contrast-enhanced Colon Rectum 1994;37:482–491. computed tomographic colonography in the follow-up 187. Moore CJ, Corl FM, Fishman EK. CT of cecal volvulus: of colorectal cancer patients: a feasibility study. Eur unraveling the image. AJR 2001;177:95–98. Radiol 2003;13:883–889. 188. Javors BR, Baker SR, Miller JA. The northern exposure 172. Schoemaker D, Black R, Giles L, Toouli J. Yearly sign: a newly described finding in sigmoid volvulus. colonoscopy, liver CT, and chest radiography do not AJR 1999;173:571–574. influence 5–year survival of colorectal cancer patients. 189. Yoshikawa A, Kuramoto S, Mimura T, et al. Peutz- Gastroenterology 1998;114:7–14. Jeghers syndrome manifesting complete intussuscep- 173. Wind P, Norklinger B, Roger V, Kahlil A, Guin E, Parc tion of the appendix and associated with a focal cancer R. Long-term prognostic value of positive peritoneal of the duodenum and a cystadenocarcinoma of the 276

ADVANCED IMAGING OF THE ABDOMEN

pancreas: report of a case. Dis Colon Rectum 207. Stewart LK,Wilson SR. Transvaginal sonography of the 1998;41:517–521. anal sphincter: reliable, or not? AJR 1999;173:179– 190. Fujimoto T, Fukuda T, Uetani M, et al. Unenhanced CT 185. findings of vascular compromise in association with 208. Rociu E,Stoker J,Eijkemans MJ,Schouten WR,Lameris intussusceptions in adults. AJR 2001;176:1167–1171. JS. Fecal incontinence: endoanal US versus endoanal 191. Hogan M, Johnson JF 3rd. Multipolypoid intussuscep- MR imaging. Radiology 1999;212:453–458. tum: a distinctive appearance of ileoileocolic intus- 209. Beets-Tan RG, Morren GL, Beets GL, et al. Measure- susception at the ileocecal valve. Pediatr Radiol ment of anal sphincter muscles: endoanal US, 1996;26:405–408. endoanal MR imaging, or phased-array MR imaging? 192. Daneman A, Alton DJ, Lobo E, Gravett J, Kim P,Ein SH. A study with healthy volunteers. Radiology 2001;220: Patterns of recurrence of intussusception in children: 81–89. a 17–year review. Pediatr Radiol 1998;28:913–919. 210. Malouf AJ, Williams AB, Halligan S, Bartram CI, 193. Gorenstein A, Raucher A, Serour F,Witzling M, Katz R. Dhillon S, Kamm MA. Prospective assessment of accu- Intussusception in children: reduction with repeated, racy of endoanal MR imaging and endosonography in delayed air enema. Radiology 1998;206:721–724. patients with fecal incontinence. AJR 2000;175: 194. Yoon CH, Kim HJ, Goo HW. Intussusception in chil- 741–745. dren: US-guided pneumatic reduction—initial experi- 211. Salzano A,De Rosa A,Amodio F,et al.[Integrated study ence. Radiology 2001;218:85–88. of fecal incontinence with defecography, anal ultra- 195. Daneman A, Alton DJ, Ein S, Wesson D, Superina R, sonography, perineography, and manometry.] [Italian] Thorner P. Perforation during attempted intussuscep- Radiol Med 1998;96:574–578. tion reduction in children—a comparison of per- 212. Ellul JP, Mannion S, Khoury GA. Spontaneous rupture foration with barium and air. Pediatr Radiol 1995;25: of the rectum with evisceration of the small intestine 81–88. through the anus. Eur J Surg 1995;161:925–927. 196. Walker M, Sylvain J, Stern H. Bowel obstruction in a 213. Spencer JA, Chapple K, Wilson D, Ward J, Windsor AC, pregnant patient with ileal pouch-anal anastomosis. Ambrose NS. Outcome after surgery for perianal [Review] Can J Surg 1997;40:471–473. fistula: predictive value of MR imaging. AJR 197. Polignano FM, Caradonna P, Maiorano E, Ferrarese S. 1998;171:403–406. Recurrence of acute colonic pseudo-obstruction in 214. Di Nardo R, Drudi FM, Marziale P, et al. [Role of color selective adrenergic dysautonomia associated with Doppler echography in the visualization of perianal infectious toxoplasmosis. Scand J Gastroenterol fistulae with injections of physiologic solutions.] 1997;32:89–94. [Italian] Radiol Med 2000;100:235–239. 198. deSouza NM, Williams AD, Wilson HJ, Gilderdale DJ, 215. Sudol-Szopinska I, Jakubowski W, Szczepkowski M, Coutts GA, Black CM. Fecal incontinence in sclero- Sarti D. Usefulness of hydrogen peroxide enhancement derma: assessment of the anal sphincter with thin- in diagnosis of anal and ano-vaginal fistulas. Eur section endoanal MR imaging. Radiology 1998;208: Radiol 2003;13:1080–1084. 529–535. 216. Maier AG, Funovics MA, Kreuzer SH, et al. Evaluation 199. Kelvin FM, Hale DS, Maglinte DD, Patten BJ, Benson JT. of perianal sepsis: comparison of anal endosonogra- Female pelvic organ prolapse: diagnostic contribution phy and magnetic resonance imaging. J Magn Reson of dynamic cystoproctography and comparison with Imaging 2001;14:254–260. physical examination. AJR 1999;173:31–37. 217. deSouza NM, Gilderdale DJ, Coutts GA, Puni R, Steiner 200. Pucciani F, Rottoli ML, Bologna A, et al. Anterior rec- RE. MRI of fistula-in-ano: a comparison of endoanal tocele and anorectal dysfunction. Int J Colorectal Dis coil with external phased array coil techniques. J 1998;11:1–9. Comput Assist Tomogr 1998;22:357–363. 201. Kelvin FM, Hale DS, Maglinte DD, Patten BJ, Benson JT. 218. Beets-Tan RG, Beets GL, van der Hoop AG, et al. Pre- Female pelvic organ prolapse: diagnostic contribution operative MR imaging of anal fistulas: Does it really of dynamic cystoproctography and comparison with help the surgeon? Radiology 2001;218:75–84. physical examination. AJR 1999;173:31–37. 219. Madsen SM, Myschetzky PS, Heldmann U, Rasmussen 202. Mellgren A, Lopez A, Schultz I, Anzen B. Rectocele is OO, Thomsen HS. Fistula in ano: evaluation with low- associated with paradoxical anal sphincter reaction. field magnetic resonance imaging (0.1 T). Scand J Gas- Int J Colorectal Dis 1998;13:13–16. troenterol 1999;34:1253–1256. 203. Salzano A, Grassi R, Habib I, et al. [The defecographic 220. Scholefield JH, Berry DP, Armitage NC, Wastie ML. and clinical aspects of the solitary rectal ulcer syn- Magnetic resonance imaging in the management of drome.] [Italian] Radiol Med 1998;95:588–592. fistula in ano. Int J Colorectal Dis 1997;12:276–279. 204. Salzano A, Muto M, De Rosa A, et al. [Defecography in 221. Lee BH, Choe DH, Lee JH, et al. Device for occlusion of rectal wall prolapse conditions.] [Italian] Radiol Med rectovaginal fistula: clinical trials. Radiology 1999;97:486–490. 1997;203:65–69. 205. Halligan S, Malouf A, Bartram CI, Marshall M, Hollings 222. Pennoyer WP, Vignati PV, Cohen JL. Mesenteric N, Kamm MA. Predictive value of impaired evacuation angiography for lower gastrointestinal hemorrhage: at proctography in diagnosing anismus. AJR are there predictors for a positive study? Dis Colon 2001;177:633–636. Rectum 1997;40:1014–1018. 206. Karoui S, Savoye-Collet C, Koning E, Leroi AM, Denis 223. Gunderman R, Leef J, Ong K, Reba R, Metz C. Scinti- P. Prevalence of anal sphincter defects revealed by graphic screening prior to visceral arteriography in sonography in 335 incontinent patients and 115 conti- acute lower gastrointestinal bleeding. J Nucl Med nent patients. AJR 1999;173:389–392. 1998;39:1081–1083. 277

COLON AND RECTUM

224. Funaki B, Kostelic JK, Lorenz J, et al. Superselective 230. Blakeborough A, Sheridan MB, Chapman AH. Compli- microcoil embolization of colonic hemorrhage. AJR cations of barium enema examinations: a survey of UK 2001;177:829–836. Consultant Radiologists 1992 to 1994. Clin Radiol 225. Duque JM, Munoz Navas M, Betes MT,Subtil JC,Angos 1997;52:142–148. R. [Colonic involvement in the Klippel-Trenaunay- 231. Shackleton KL, Stewart ET, Henderson JD Jr, Demeure Weber syndrome.] [Review] [Spanish] Rev Esp Enferm MJ, Telford GL. Effect of barium sulfate on wound Dig 2000;92:44–45. healing in the gastrointestinal tract of the rat. Radiol- 226. Gonzalez Valverde FM, Mendez Martinez M, Osma ogy 2000;214:563–567. Cordoba MD, Ballester Moreno A. [Small bowel lym- 232. Sasatomi E, Miyazaki K, Mori M, Satoh T, Nakano S, phoma associated to carcinoid of the duodenum and Tokunaga O. Polypoid adenomyoma of the gallbladder. angiodysplasia of the colon.] [Spanish] Rev Esp J Gastroenterol 1997;32:704–707. Enferm Dig 1999;91:312–313. 233. Ryan CK, Potter GD. Disinfectant colitis. Rinse as well 227. Cacoub P, Sbai A, Benhamou Y, Godeau P, Piette JC. as you wash. [Review] J Clin Gastroenterol 1995;21: [Severe gastrointestinal hemorrhage secondary to 6–9. diffuse angiodysplasia: efficacy of estrogen-proges- 234. Damore LJ 2nd,Rantis PC,Vernava AM 3rd,Longo WE. terone treatment.] [French] Presse Med 2000;29: Colonoscopic perforations. Etiology, diagnosis, and 139–141. management. [Review] Dis Colon Rectum 1996;39: 228. Guingrich JA, Kuhlman JE. Colonic wall thickening in 1308–1314. patients with cirrhosis: CT findings and clinical impli- 235. Hirata K, Noguchi J, Yoshikawa I, et al. Acute appen- cations. AJR 1999;172:919–924. dicitis immediately after colonoscopy. Am J Gastroen- 229. Hung CC, Wong JM, Hsueh PR, Hsieh SM, Chen MY. terol 1996;91:2239–2240. Intestinal obstruction and peritonitis resulting from gastrointestinal histoplasmosis in an AIDS patient. J Formos Med Assoc 1998;97:577–580.