TC Rectal Pathology: Findings at CT-Colonography

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Radiología. 2018;60(3):208---216

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RADIOLOGY THROUGH IMAGES

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TC rectal pathology: Findings at CT-colonography

∗

M.J. Martínez-Sapina˜ Llanas, S.A. Otero Muinelo , C. Crespo García

Servicio de Radiodiagnóstico, Complexo Hospitalario Universitario de A Coruna,˜ A Coruna,˜ Spain

Received 28 March 2017; accepted 19 October 2017

KEYWORDS Abstract

CT-colonography; Objective: To review the spectrum of benign and malignant rectal diseases, their ﬁndings on

Pathology; CT colonography, and their management.

Rectum; Conclusion: Although CT colonography is not the ﬁrst choice for the study of rectal disease, it is

Cancer; indicated in cases where optical colonoscopy is contraindicated or cannot be completed. Rectal

Technique lesions can go undetected because this anatomic area is difﬁcult to evaluate; for this reason,

it is essential to ensure optimal preparation and distension, moderate balloon insufﬂation, and

careful 2D and 3D navigation with knowledge of the spectrum of rectal disease and its CT

colonography signs.

PALABRAS CLAVE Patología del recto: hallazgos en la colonografía-TC Colonografía-TC;

Patología; Resumen

Recto; Objetivo: Revisar el espectro de la patología rectal benigna y maligna, sus hallazgos en la

Cáncer; colonografía-TC (CTC) y su manejo.

Técnica Conclusión: Aunque la CTC no es la herramienta de primera elección para el estudio de la

patología rectal, está indicada en casos de colonoscopia óptica incompleta o contraindicada.

Las lesiones rectales pueden pasar desapercibidas por la diﬁcultad que representa la valoración

de esta área anatómica, y por ello es necesaria una excelente preparación y distensión, la

insuﬂación moderada del balón y una navegación cuidadosa en 2D y 3D con conocimiento del

espectro de la patología rectal y su semiología en CTC.

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Please cite this article as: Martínez-Sapina˜ Llanas MJ, Otero Muinelo SA, Crespo García C. Patología del recto: hallazgos en la colonografía-

TC. Radiología. 2018;60:208---216. ∗

Corresponding author.

E-mail address: [email protected] (S.A. Otero Muinelo).

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TC rectal pathology: Findings at CT-colonography 209

Table 1 Contraindications of the optical colonoscopy Table 4 Colonic preparation for the CT-colonography.

procedure.

• Diet without ﬁber three (3) days prior to the examination

Absolute contraindications • Complete diet with liquid food supplement (Isosource )

• Severe pulmonary or heart disease one (1) day prior to the examination

• Diathesis, bleeding, or treatment with anticoagulants • Oral iodinated contrast (diatriazoate): 3 doses of 7 cc

• Risks due to sedation diluted in water two (2) days prior to the examination,

• Patient refusing to undergo the procedure and 5 doses of 7 cc diluted in water one (1) day prior to

the examination

Relative contraindications ®

• Microenema of local action (Micralax ) ﬁrst time in the

• Prior history of incomplete optical colonoscopy

morning of the examination day; immediately prior to

• Advanced age

the CTC, evacuation of the rectal ampulla

• Weak patient and with mobility issues

• Take 2 l of water a day as a complement to the whole

preparation

Introduction • Optional: prescription of intramuscular bowel muscle

relaxants (Buscopan ) one (1) hour prior to the test; they

Rectal pathology is varied and prevalent and, although the are contraindicated in cases of glaucoma, prostatic

most serious lesion is the carcinoma, in most cases the hypertrophy, heart disease, severe myasthenia gravis, or

lesion is usually benign. The optical colonoscopy (OC) is porphyria

the standard imaging modality for its study since it entirely

evaluates the rectum in most cases. Nonetheless, the OC

procedure is an invasive imaging modality with associ-

ated risks such as perforation, bleeding, and complications The assessment of the anorectal region using the CTC

following sedation. Whenever the OC is contraindicated is especially problematic due to a wide range of unique

(Table 1) or is incomplete (10---15% of the times ), the com- pathologies in this area, the presence of a rectal balloon

1,2

puted tomography-colonography (CTC). is indicated. In catheter, the possible artifacts, and the particular funicular

other occasions, the CTC is conducted as the ﬁrst imaging morphology of the anal canal, which all may lead to false

3 --- 7 13---15

modality for the screening of colorectal cancer. positive ﬁndings or conceal serious pathologies. The rec-

The CTC is a quick, non-invasive emerging imaging modal- tum is the most common location of hidden cancers in the

ity developed for the screening of colorectal cancer and CTC.

approved by the American Cancer Society back in 2008. It The goal of this article is to get to know the rectal pathol-

is usually implemented as an alternative to the incomplete ogy, its semiology in the CTC and its management.

or contraindicated OC and is considered the most suitable

radiological imaging modality for the screening of colorec-

tal cancer and polyps. Its diagnostic performance for the Technical considerations

detection of cancer is similar to that of the OC, and clearly

superior to the barium enema. Conducting one CTC requires one 8-row multidetector CT

The CTC allows us to perform easy, well-tolerated, and machine, the adequate preparation and distension of the

2 1

almost risk-free 2D and 3D examinations of the colon, and it colon, and speciﬁc software.

9,10

is also capable of showing extracolonic ﬁndings using low The preparation of the colon (Table 4) is essential here,

doses and no IV contrast. The CTC has different indications since the residual fecal matter can simulate or hide lesions,

3,11 12

(Table 2), and very few contraindications (Table 3). and an inadequate distension won’t let us assess the colonic

3,15,17,18

wall or surface.

One moderately inﬂated balloon catheter is inserted into

Table 2 Indications of the CT-colonography.

the rectum after an optional, although recommended, dig-

•

Contraindicated optical colonoscopy ital examination. Distension can be manual, using ambient

•

Incomplete optical colonoscopy air, or preferably automatic with CO2. The whole process

•

Patient refusal to undergo the optical colonoscopy starts in the right lateral decubitus position and different

procedure series are acquired both in the supine decubitus and prone

12---17

•

Assessment of diverticular disease (after the acute phase) positions without IV contrast. It is advisable to partially

•

Assessment of patients with colonic stoma deﬂate the balloon in its helix in the prone position so that

•

Other indications: no adjacent lesions are blocked. If a segment is found that

•

Screening of colorectal cancer remains persistently collapsed, then a third helix should be

17,18

•

Controls after colorectal cancer surgery or polypectomy acquired in the lateral decubitus position.

If available, protocols with a low-dose of radiation and

iterative reconstruction are used.

Table 3 Contraindications of the CT-colonography.

In the presence of a known tumor, the staging process

with the use of contrast in one of the series is optional.

• Acute bowel inﬂammatory disease

The analysis of the images obtained allows 2D

• Acute diverticulitis

(axial images and multiplanar reconstructions) and 3D

• Recent surgery (<3 months)

endoluminal views with anterograde and retrograde navi-

• Inguinal hernia with colonic content

gation visualizations. Post-processing tools are virtual

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210 M.J. Martínez-Sapina˜ Llanas et al.

Table 5 Classiﬁcation of colonic polyps.

Based on their morphology Based on their size

• Sessile: wide base of • Tiny: <6 mm

implantation

• Pedunculated: with stalk or • Intermediate: 6 --- 9 mm

pedicle

• Flat: protrude <3 mm over the • Large: ≥10 mm

mucosa; carpet lesions are ﬂat

lesions >3 cm in size that usually

affect the caecum and the

rectum

dissection, virtual biopsy or translucency, second readings,

and the electronic subtraction of ﬂuid and feces.

We should remember that for the adequate assess-

ment of the rectal region, an excellent colonic

Figure 1 Rectal polyps. Coexistence of different polypoid

preparation and distension are needed. The balloon

lesions in the rectum: pedunculated polyp (white arrow), sessile

should be moderately deﬂated in its helix in the decu-

polyp (arrowhead), rectal balloon (asterisk).

bitus prone position.

We should remember that the target lesion of the

Rectal pathology

CTC is the advanced adenoma: polyp ≥10 mm, villous

component >25%, or high-grade dysplasia. There is a

Rectal pathology includes processes of very different ori-

direct correlation between size and malignancy risk.

gin: congenital, acquired, tumors, inﬂammatory, vascular,

or artifactual. Although the most severe lesions are carcino-

mas and lymphomas, we may ﬁnd a wide variety of benign

lesions in the rectum. Villous tumors

Polyps They are rare in the rectum and represent 5% of all colorec-

tal neoplasms. They are large in size, and have a lobular

They are homogeneous attenuation structures of soft appearance on the CTC, which is consistent with the dense

tissues that originate in the mucosa and project toward the appearance seen on the OC. They have a higher risk of

lumen. They may be found anywhere in the colon and are degeneration (Fig. 2). The diagnosis should be conﬁrmed

common in the rectum, where the rectal catheter can end through OC and biopsy.

up masking them.

They are classiﬁed based on their morphology and size

17 Malignant neoplasms

(Table 5), being this the criterion that stratiﬁes its malig-

nant potential.

Of variable morphology, they may present as small or big size

The goal of the CTC is to detect advanced adenomas:

stenosing or polypoid lesions. The most difﬁcult cancers to

polyps ≥10 mm, villous component >25, or high-grade dys-

detect are the small ones, since they can remain kind of

plasia. Size should be assessed in both helixes through 2D

13 hidden by the balloon catheter and look like polypoid focal

and 3D visualizations, and also in the plane that better

16 thickenings (Fig. 3), which is why it is advisable to slightly

shows its actual dimension.

deﬂate the balloon in its helix in the decubitus prone posi-

Rectal polyps can be single or multiple polyps, be part

tion. Between 1.5% and 6% of all colonic neoplasms associate

of polyposis syndromes, and coexist with other conditions

synchronic lesions (Fig. 4). The CTC is especially useful if the (Fig. 1).

1,9,19

distal lesion is oclusive.

For screening purposes, polyps ≥6 mm identiﬁed through

One rectal lesion suspicious of malignancy on the CTC

the CTC should appear in the radiological report, being

should be biopsized with CO.

the endoscopic polypectomy the recommended procedure

here. CTC monitoring is an alternative in patients where

the polypectomy is risky and with one or two polyps of

intermediate size. Polyps ≥10 mm should undergo endo- We should remember that the biggest problem when

scopic polypectomy procedures. Polyps <5 mm are difﬁcult it comes to the anorectal region is misdiagnosing low

to detect on the CTC, grow slowly and have a low malignancy malignant lesions hidden by the balloon catheter or

risk; however, the European Society of Gastrointestinal and darkened by the artifacts.

Abdominal Radiology recommends reporting polyps >3 mm

when they have been safely detected.

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TC rectal pathology: Findings at CT-colonography 211

Figure 2 Villous tumor. (a) Axial CT image. Lobulated lesion based on the lateral wall of the rectum (white arrow). The soft cover

of its surface after the administration of oral contrast shows its dense appearance. (b) Match with 3D view. The anatomopathological

ﬁnding was villous adenoma.

Figure 3 Carcinoma. (a) This axial CTC image corresponds to one patient studied due to anemia and shows one ﬂat mural lesion

in the rectum discretely protruding toward the lumen (arrow) that turned out to be an adenocarcinoma in the cylinder biopsy. (b)

3D virtual colonoscopy. (c) Optical colonoscopy.

Figure 4 Synchronic neoplasms. CTC of a seventy-ﬁve-year-old woman after an incomplete optical colonoscopy due to occlusive

stenosing lesion in her rectum. (a) Axial CT image. Lesion inside the distal rectum (arrow) corresponding with one polypoid elevated

lesion (b, 3D endoluminal view) consistent with one carcinoma. The CTC was good for the detection of another lesion of malignant

appearance in the sigma (c). Note the beam hardening artifact caused by the metallic prosthetic material in both hips (a), which

makes the assessment of the rectum even more difﬁcult.

Submucosal lesions lesions, the primary rectal lymphoma is relatively rare com-

pared to the small intestine gastric lymphoma. Almost all

of them are non-Hodgkin lymphomas type B associated with

There is a wide variety of benign and malignant condi-

immunosuppression and bowel inﬂammatory disease. On the

tions (Table 6). They originate in deep areas (intramural or

OC they appear as one big polilobulated or multifocal single

extramural), protrude toward the intestinal lumen, make up

mass (Fig. 5).

obtuse angles with the wall and displace the folds without

12 The CTC assessment of alleged submucosal lesions found

interrupting them.

on the OC is useful to be able to distinguish an intramural

The most common of all are lipomas that can be easily

process from an extramural extrinsic compression, identify

identiﬁed by their fat density. When it comes to malignant

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212 M.J. Martínez-Sapina˜ Llanas et al.

Figure 5 Lymphoma. (a) CT image reconstruction in the sagittal plane. Diffuse thickening of the wall of the rectum and sigma

(black arrows). (b) Virtual luminogram. Loss of distension in the damaged segments (arrowheads). Note the loss of haustration of

the descending colon (hollow arrows) relative to ulcerative colitis in chronic stage. (c) Virtual colonoscopy. Stenotic appearance of

submucosal masses in intestinal lymphoma.

Figure 6 Extramural submucosal lesion. Sixty-eight-year-old woman with abdominal pain. (a) CTC, virtual luminogram. Repletion

defect in the lateral wall of the rectum (thick arrow) that looks like an extrinsic compression on the 3D endoluminal image (thick

arrow in b). (c) The axial CT image shows one extramural submucosal ﬂuid density lesion (white arrow) exerting that extrinsic

compression and consistent with a developing cyst. The thin arrows in (a) and (b) point at the rectal balloon.

13,14

its true nature, and study the spread of the disease

Table 6 Submucosal lesions.

(Fig. 6).

Of intramural origin Of extramural origin Management can vary. Fat density characterizes lipomas

and is diagnostic on the 2D images. In other submu-

• Leiomyoma • Endometriosis

cosal lesions, other imaging modalities (MRI, transrectal

• Lipoma • Developmental retrorectal

ultrasound. . .) may help us characterize these lesions.

cystic lesions:

We should remember that the CTC allows us to distinguish

• Neuroendocrine tumor --- Retrorectal cystic

hamartoma intramural from extramural submucosal lesions, identify

their true nature, and study the spread of the disease.

• Gastrointestinal stromal --- Rectal duplication

tumor

• Schwannoma --- Epidermoid cyst

Vascular lesions

• Lymphoma --- Dermoid cyst

• Melanoma • Rectal invasion by other

• Internal hemorrhoids: it is the most common rectal

tumors

pathology. It consists of the dilation of the veins of the

• Other primary tumors 13

superior plexus that are covered by the mucosa over

• Metastasis 14

the dentate line. They have a typical appearance on

the CTC, of anorectal location, and on circumferential

disposition around the catheter, giving the appearance

of one submucosal lesion, or a wrinkled appearance of

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TC rectal pathology: Findings at CT-colonography 213

Figure 7 Rectal varicose vein. Eighty-year-old male with anemia and rectorrhagy. (a) Axial CTC image. Parietal lesion in his

rectum of soft tissue density (white arrow). (b) 3D CTC. The black arrow shows the tubular and winding morphology of the lesion

objectiﬁed in (a). Rectal catheter (asterisk). (c) Rectal varicose veins as seen on the optical colonoscopy (arrow).

Figure 8 Hypertrophied anal papilla. Fifty-seven-year-old-woman. CTC after incomplete optical colonoscopy. (a) 2D image on

the axial plane. Lesion in the rectal lumen stained in its periphery after the administration of oral contrast (white arrow). (b)

3D endoluminal view. The arrow points at the same lesion in contact with the rectal balloon (asterisk) and close to the anorectal

junction (c) The optical colonoscopy conﬁrms it is consistent with one hypertrophied anal papilla (white arrow).

the mucosa around the rectal tube. When hemorrhoids • Rectal varices: they are less common than internal hemor-

become thrombosed they may look like a tumor. The rhoids, associate portal hypertension, and have a winding

rectal touch, instead of the OC, may help conﬁrm the and tubular morphology (Fig. 7). Diagnosis is achieved

diagnosis. through the OC.

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214 M.J. Martínez-Sapina˜ Llanas et al.

Figure 9 Actinic proctitis. CTC in one patient with cervical carcinoma treated with radiation therapy after incomplete optical

colonoscopy due to impassable stenosis. (a) CT image reconstruction in the coronal plane that reveals protrusions (arrows) and

stenoses (not shown). (b) The 3D image shows one of the polypoid lesions that looks ulcerative in the optical colonoscopy (c).

• Venous malformations: they are rare. They may be part of The CTC outside the acute episode allows us to assess the

the blue rubber bleb nevus syndrome or appear in isolation degree of stenosis and plan the course of treatment.

on the CTC simulating one polyp. On the OC they show a The solitary rectal ulcer consists of an intense inﬂamma-

characteristic blue color. On the MRI, their hyperintensity tory reaction around an ulcer that conditions one mass effect

on the T2-weighted sequences and their spread into the that can be interpreted as a malignant tumor in a patient

20 13

mesorectal fat are speciﬁc characteristics. with rectorrhagy and painful defectation. Both the OC and

the biopsy are indicated to achieve the diagnosis.

Papillary hypertrophy

Postoperative changes

They are focal ﬁbrous protrusions on the dentate line. They

may look like polyps, but their location in the anorectal junc-

The surgical clips placed on colorectal anastomoses usually

tion is patognomonic, and almost always in contact with the

appear on the 3D images as irregularities of the mucosa that

catheter (Fig. 8). The OC is diagnostic.

can be taken for tumor relapses. The 2D images are key here

since they reveal their metallic density (Fig. 10).

Inﬂammatory conditions Rectocolonic anastomoses are a common cause of incom-

plete OCs, but they rarely cause signiﬁcant stenoses.

The rectum is affected in the ulcerative colitis and Chron’s The signs of recurrence of neoplastic disease are

disease whenever there is associated perianal disease. The irregularity, wall thickening, and distortion of the mucosal

radiation therapy-related iatrogenia in the pelvis affects the pattern compared to common postoperative ﬁndings such as

rectum in the form of actinic proctitis. These conditions small size inﬂammatory polyps located in the anastomotic

appear as one diffuse, circumferential thickening of the wall line.

of the rectum that causes variable stenoses, with impor- In the presence of suspicious images and suspicion of

tant frequencies, but with signs of benignity. The patient’s relapse, we should try to biopsize with the OC, or else, with

personal history facilitates the diagnosis (Fig. 9). a surgical biopsy in cases of impassable stenoses.

Figure 10 Surgical material. (a) The 3D image shows a signiﬁcant mucosal irregularity inside one rectal valve (black arrow). The

CTC image on the axial plane (b) shows material of metallic density (white arrow), and eventually tumor pathology is ruled out

after the OC conﬁrms the presence of surgical clips (c).

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TC rectal pathology: Findings at CT-colonography 215

Figure 11 Rectal balloon catheter. (a) The distal end of the rectal catheter (black arrow) can compress the rectal valves (arrow-

head) and create an image of submucosal extrinsic compression. (b) 3D image. Appearance of the catheter protrusion over the

rectal valve. (c) The position of the balloon catheter needs to be conﬁrmed on the multiplanar reconstructions.

Pseudolesions and artifacts the CTC, have an excellent command while performing the

technique when it comes to preparation and distension, con-

With an optimal fecal marking and colonic distention, most duct moderate balloon insufﬂations, and careful 2D and 3D

artifacts are easily recognizable: navigations.

• The rectal catheter: constant ﬁnding in the anorectal

13,14 Authors

region. Its tip can have a polypoid appearance on the

3D views, or cause compression on an adjacent rectal fold.

1. Manager of the integrity of the study: MJMSL, SAOM and

Both the partial balloon deﬂating in the decubitus prone

14 CCG.

position and the veriﬁcation of its presence on the 2D

2. Study idea: MJMSL, SAOM and CCG.

images (Fig. 11) are of great help.

3. Study design: MJMSL, SAOM and CCG.

• Stained feces: they may appear as polyps or masses based

14 4. Data mining: MJMSL, SAOM and CCG.

on their size on the 3D endoluminal images, but they

5. Data analysis and interpretation: MJMSL, SAOM and

can be easily identiﬁed on the 2D images after contrast

staining.13,17 CCG.

14 6. Statistical analyses N/A.

• Unstained feces: they can be a problem if they are small.

7. Reference: MJMSL, SAOM and CCG.

Internal air foci and supine-to-prone position changes are

13,17 8. Writing: MJMSL, SAOM and CCG.

characteristic here.

9. Critical review of the manuscript with intellectually rel-

• Fecalomas: they are common in the rectal ampulla. The

evant remarks: MJMSL, SAOM and CCG.

3 D endoluminal image shows one lobulated irregular mass

10. Approval of ﬁnal version: MJMSL, SAOM and CCG.

that simulates a tumor or cancer. The 2D image is diag-

nostic and shows the heterogeneous composition that is

typical of unstained feces.

Ethical responsibilities

Other lesions

Protection of people and animals. The authors declare that

no experiments with human beings or animals have been

The condyloma acuminatum can present as a polypoid

performed while conducting this investigation.

lesion, although it is rare. The diagnosis of anorectal lesions

is achieved through anoscopy examination or rectal touch.

The diverticula are exceptional in the rectum. They look Data conﬁdentiality. The authors declare that they have

exactly the same in all colonic locations, and their ﬁnding followed their center protocols on the publication of data

does not require follow-up or diagnostic conﬁrmation. from patients.

Conclusion Right to privacy and informed consent. The authors con-

ﬁrm that in this article there are no data from patients.

Although rectal lesions can go misdiagnosed on the CTC

because it is particularly difﬁcult to assess this anatomical

region, and even though it is not the modality of choice Conﬂict of interest

for the study of rectal pathologies, it is indicated in cases

of incomplete or contraindicated OCs. For this reason, it is The authors declare no conﬂict of interest associated with

essential to know the rectal pathology and its semiology on this article whatsoever.

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216 M.J. Martínez-Sapina˜ Llanas et al.

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