Ultrasound and the Nonacute Abdomen: the Abdominal Organs

IN-DEPTH: ULTRASOUND OF THE THORAX AND ABDOMEN

Ultrasound and the Nonacute Abdomen: The Abdominal Organs

Mary Beth Whitcomb, DVM

The ability of ultrasound to detect abnormalities of the kidneys, liver, and spleen has made tremen- dous strides over the past 10 years due to technological advancements in ultrasound equipment and increased availability of skilled equine ultrasonologists. As our knowledge base continues to grow, increased awareness is important for owners and veterinarians to understand the diagnostic potential of abdominal ultrasound. Evaluation of abdominal organs is best performed as part of a complete abdominal ultrasound exam. Ultrasound-guided procedures are often required to differentiate between various infectious, inﬂammatory, and neoplastic disorders. Author’s address: Clinical Large Animal Ultrasound, Department of Surgical and Radiological Sciences, University of California, One Shields Avenue, Davis, CA 95616; e-mail: [email protected]. © 2012 AAEP.

1. Introduction Admittedly, mastery of abdominal ultrasound re- Evaluation of the abdominal organs, including the quires experience and patience, much more so than kidneys, liver, and spleen, is generally performed as basic ultrasound of the acute abdomen. Similar to part of a complete ultrasound examination in non- any anatomic region, however, cursory examination acute patients.1 Many horses with hepatic, renal, is possible by a motivated practitioner equipped or splenic abnormalities present with nonspecific with appropriate ultrasound equipment. It is clinical signs3–6 similar to those in horses with gas- equally important for field practitioners to under- trointestinal tract disorders. Complete blood count stand our increased ability to diagnose and treat (CBC) and serum chemistry analysis may be unre- disorders of abdominal organs in the referral set- markable or show only evidence of inflammation ting. Ultrasound findings often help guide treat- such as hyperfibrinogenemia and hyperglobuline- ment planning, including the need for medical mia. Subsequently, a full exam is required to max- therapy or surgical intervention. Not only do we imize diagnostic yield in many cases. In other gain valuable information about the appearance of horses, clinical exam findings and serum biochemis- abdominal organs, ultrasound-guided biopsy and/or try analysis may indicate primary renal or hepatic aspirate can be used to determine the underlying etiology, to establish an appropriate treatment plan, disease, in which case the examiner may choose to 1–2 focus on the urinary tract or liver, respectively. and for prognostication. Although horses with abdominal organ disorders infrequently present as acute colic patients, cursory Ultrasonographic Technique examination of abdominal organs can yield important A low-frequency (2–5 MHz) curvilinear transducer is information during routine colic ultrasound exams. necessary to evaluate abdominal organs in the adult

NOTES

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C O C L O O L R O Fig. 1. Region to be clipped for complete abdominal ultra- R sound. The left abdomen is clipped in similar fashion. Fig. 2. Time-gain compensation controls adjusted properly for deep cavity imaging.

horse due to their deep location (15 to 30 cm) relative to the skin surface. This transducer is available for ventral abdomen. Structures evaluated from the most of today’s ultrasound machines, the majority of left side of the abdomen include the left kidney, which are able to obtain exceptionally high-quality spleen, stomach, and left liver lobe. The left dorsal abdominal images. In contrast, a rectal transducer and ventral colons are seen predominantly from the can only penetrate to 5 to 10 cm, which is insuffi- left ventral abdomen. cient to image the left kidney and the majority of the Scanning depth should be adjusted frequently spleen, liver, and right kidney from the transcuta- during the exam to best image the superficial and neous window. A rectal transducer can be used to deep parenchyma of each organ. No single depth image the caudal portion of the left kidney and setting is appropriate for all abdominal organ imag- spleen during transrectal examination. ing. An abdominal program or preset should be For the highest quality images, the entire abdo- selected to maximize abdominal detail. Time-gain men should be clipped with #40 blades, especially in compensation controls should also be adjusted for older, obese, or thick-coated horses that tend to im- deep cavity imaging (Fig. 2). F2 F1 age poorly (Fig. 1). Alcohol saturation can produce diagnostic quality images, but the subtle nature of Renal and Urinary Tract Ultrasound many ultrasonographic findings in the nonacute ab- Specific indications for renal ultrasound include domen may not be detectable without clipping. azotemia, hematuria, pollakiuria, dysuria, or abnor- After clipping, the skin should be cleaned with a wet mal findings of cystoliths, ureteroliths, or left renal sponge to remove dirt and debris, and ultrasound gel enlargement on rectal palpation.7–11 It is impor- is then applied. tant to remember that horses with significant renal A systematic approach to each exam is important abnormalities may present with a normal CBC and for consistency and to improve diagnostic yield. serum biochemical profile.12 At the University of California, Davis (UC Davis), The left kidney is visible transcutaneously and the entire abdomen is evaluated in the majority of transrectally. Transcutaneously, the left kidney is nonacute patients presenting to the Large Animal located deep to the spleen in the left PLF region and Ultrasound Service. Each side of the abdomen is the left 15th to 17th ICS at a scanning depth of 20 to divided into three regions: (1) paralumbar fossa/ 30 cm (Fig. 3). The best images are often obtained F3 flank region (PLF); (2) 5th through 17th intercostal in the left 16th to 17th ICS; however, the kidney spaces (ICS) from the ventral lung margins to the should be imaged from all possible windows. At costochondral junctions; and (3) ventral abdomen UC Davis, we routinely use a “special” technique to from the sternum to the inguinal region. The exam image the left kidney that entails placing the trans- should be performed in the same manner, regardless ducer caudal to the last rib, midway between the of clinical suspicion of cause. Structures evaluated tuber coxae and stifle, and aiming in a dorsocranial from the right side of the abdomen include the ce- direction. By applying gradual force with each ex- cum and cecal mesentery, right kidney, right liver piration, the transducer is effectively brought closer lobe, duodenum, and right dorsal colon. The right to the left kidney and a superior image obtained ventral colon is primarily visualized from the right than with traditional techniques. Transrectally,

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C O C L O O L R O R Fig. 3. Normal appearance of the left kidney (LK) as seen from the left 16th ICS. The renal cortex is hypoechoic to the adjacent Fig. 4. Ultrasonographic appearance of an end-stage left kidney spleen and a clear corticomedullary junction is visible. Dorsal is in a horse with chronic renal failure. The kidney is small and to the right. shows large hyperechoic areas consistent with fibrosis, scarring, nephrolithiasis, or mineralization. Renal parenchyma is nearly unrecognizable. Dorsal is to the right. the left kidney is typically visible at arm’s length; however, only the caudal portion of the kidney can be seen. The right kidney is seen dorsally in the th th Renal parenchyma is seldom distorted in horses right 15 to 17 ICS at a more superficial scanning with acute renal failure; however, a clearly visible depth of 15 to 20 cm, compared with the left kidney. and discrete corticomedullary junction is often pres- The right kidney cannot be imaged transrectally in ent. Renal abscesses have been reported and ap- most horses. pear as variably shaped hypoechoic or hyperechoic Renal ultrasonographic parameters include size, areas within the renal cortex and/or medulla.12 shape, cortical echogenicity (hypoechoic to the adja- The kidneys are the second most common abdominal cent spleen), cortical thickness, medullary echoge- organ to be affected in horses with internal Coryne- nicity (hypoechoic to the cortex), and bacterium pseudotuberculosis infection. Care corticomedullary distinction. The renal pelvis should be taken not to misinterpret the hypoechoic should be evaluated for the presence of nephroliths area visible in the deep medullary portion of the and dilation (pyelectasia). Reported renal size right kidney for a mass or abscess. Hematuria is measurements are somewhat variable, and horse not uncommon in horses with renal abscessation. size should be considered when interpreting mea- Renal neoplasia is relatively uncommon in horses surements. In our experience, normal adult kid- but may be encountered with some regularity at neys range from 5 to 9 cm in width and 15 to 19 cm referral hospitals. Renal adenocarcinoma is the in length; however, a recent study reported smaller most common primary tumor, producing large measurements than that described by Reef and that 1,13 masses that completely efface renal parenchyma of our own clinical experience. 14,15 (Fig. 6). Renal mestastasis of other tumor F6 Small kidneys are generally associated with types has also been reported.1 chronic renal failure.7 Affected kidneys often show a distorted shape, increased cortical echogenicity and thickness, and poor corticomedullary distinction and may have nephrolith(s) or peripelvic mineralization. Some are nearly unrecognizable as kid- F4 neys (Fig. 4). In some horses with chronic renal failure, one kidney may appear to be end-stage and nonfunctional, with the contralateral kidney showing enlargement but relatively normal renal parenchyma.7 Enlarged kidneys with or without increased cortical echogenicity and thickness may be secondary to C acute renal failure, urolithiasis, nephritis, pyelone- O phritis, hydronephrosis, abscessation, or, less com- L 1,7,9–12 O monly, neoplasia. Interventional procedures R such as ultrasound-guided biopsy or aspirate are often necessary to differentiate between potential Fig. 5. Perirenal edema (arrows) in a 4-day-old foal with acute diagnoses. Horses with acute renal failure may renal failure. Note the distinct corticomedullary junction that is have perirenal edema, seen as an anechoic fluid often noted in horses with acute renal failure. Dorsal is to the F5 layer between the renal capsule and cortex (Fig. 5). right.

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Orig. Op. OPERATOR: Session PROOF: PE’s: AA’s: 4/Color Figure(s) ARTNO: 1st disk, 2nd beb spencers 12 1-23 3280 IN-DEPTH: ULTRASOUND OF THE THORAX AND ABDOMEN

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Fig. 6. Renal enlargement and diffuse effacement of renal pa- Fig. 8. Transrectal image of a large cystolith (arrow) within the renchyma in a horse with renal adenocarcinoma of the left kid- urinary bladder of a 20-year-old Arabian gelding with hematuria. ney, visualized from the left paralumbar fossa region. Dorsal is to the right.

ters are evaluated individually (Fig. 9), beginning at F9 the bladder trigone and following each as far crani- Horses with urolithiasis can present with hema- ally as possible. The left ureter can regularly be turia after exercise, azotemia, and occasionally with 8,10,11 followed along its length to the left kidney. The signs of colic. Urolithiasis is regularly en- majority of the right ureter is also visible; however, countered by clinicians at our hospital. Nephro- the ureteropelvic junction with the right kidney is liths are easily recognized as hyperechoic structures rarely visible in normal or abnormal horses. The within the renal pelvis that cast hard shadows (Fig. presence of ureteral motility is helpful to differenti- F7 7). Renal sludge appears similarly but may pro- ate ureters from blood vessels and the vas deferens duce a “dirty” or less distinct shadow. Differentia- in male horses. The normal appearance of the cau- tion between nephroliths and renal sludge is not dal ureters has been described.16 Ureteroliths can straightforward. Care should be taken not to mis- be identiﬁed along the length of the ureter (Fig. 10). F10 interpret the hyperechoic appearance of the renal In the author’s experience, urolithiasis is often as- pelvis as nephrolithiasis. All horses with urolithi- sociated with ureteral wall thickening regardless of asis should undergo transcutaneous evaluation of the location of the stone. Most importantly, in both kidneys and transrectal evaluation of the en- cases of urolithiasis, the examiner should be re- tire urinary tract to rule out additional uroliths and minded to perform bladder endoscopy after ultra- for evidence of underlying renal disease. Transrec- sound examination. Gas that is introduced during tal evaluation of the bladder and ureters is also endoscopy will obscure ultrasonographic visualiza- indicated in horses with distention of the renal pel- tion of urinary structures, and its hyperechoic ap- F8 vis because a downstream cystolith (Fig. 8) or uret- pearance can be easily confused with uroliths. erolith may be the cause for renal pyelectasia. Idiopathic renal hematuria should be a differen- Using a transrectal approach, the left and right ure- tial in horses with a large amount of frank blood in their urine.8,10 Affected kidneys show distention of the renal pelvis with echogenic material consistent with hemorrhage and clot formation. Renal archi-

C O L O R C O Fig. 7. Large nephrolith within the renal pelvis of the left kid- L ney, visible from the left paralumbar fossa region, in a horse that O presented for pollakiuria and microscopic hematuria due to a R bladder stone. The horse had a previous bladder stone removed 3 years earlier, at which time nephroliths were also noted. Dor- Fig. 9. Normal transrectal image of the midportion of the right sal is to the right. ureter.

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C O C L O O L R O R Fig. 10. Transrectal image of an obstructive ureterolith within the proximal portion of the right ureter in a 14-year-old Quarter Fig. 11. Normal transcutaneous image of the right liver lobe th Horse mare with persistent azotemia despite the removal of sev- (RLL) obtained from the right 13 ICS showing normal sharp eral bladder stones 5 months prior. Right renal ultrasound re- margins, echotexture, and ﬁne vascular markings. Dorsal is to vealed severe distention of the renal pelvis with echogenic the right. material.

it may occasionally be positioned deep to the spleen, tecture is often otherwise unremarkable. Horses in which case the LLL margins will appear falsely are typically unilaterally affected. Removal of the rounded. Echogenicity of the LLL should be hy- affected kidney has not been reported to be effective poechoic to the adjacent spleen (Fig. 12). Scanning F12 because the contralateral kidney may subsequently depth ranges from 10 to 30 cm and should be become affected. Biopsy has not been rewarding in changed in each ICS to best evaluate the superficial horses to reveal the underlying cause of idiopathic and deep parenchyma of the liver. renal hematuria. Ultrasonographic abnormalities include hepato- Renal cysts may be identified as an incidental megaly, rounded margins (Fig. 13), changes in echo- F13 finding in normal horses. In such cases, a singular genicity (usually increased), decreased fine vascular cyst is typically present. Multiple small cortical markings, biliary/vascular fibrosis/inflammation, cysts may be found in horses with acute or chronic hepatoliths, biliary distention, and, less commonly, renal failure. evidence of abscessation or neoplasia. Hepatomeg- aly and rounded margins may be seen with multiple Liver disease processes, including hepatitis, cholangio- hepatitis, obstructive cholelithiasis, and neopla- The liver is generally evaluated as part of a complete 17,18 abdominal ultrasound but may be the primary focus sia. Decreased fine vascular marking (FVM) is in horses with elevated hepatic enzymes. Similar a nonspecific but significant finding and is often to horses with renal disease, horses with significant overlooked by less experienced imagers due to its hepatic abnormalities may have normal hepatic en- subtle nature. Decreased FVM causes the liver to zymes.12 In such cases, clinicians should resist the appear dense and similar in echotexture to the temptation to dismiss abnormal hepatic ultrasound spleen. It may be the only sonographic abnormal- findings as a potential cause of clinical signs. Bi- ity in some horses with primary liver disease, in- opsy may prove useful to document the presence of active liver disease in such cases. The right liver lobe (RLL) is visible ventral to the th th F11 lung margins in the right 8 to 15 ICS (Fig. 11), although visibility can be quite variable within these ICS. The RLL should not extend to or beyond the costochondral (CC) junctions, in which case it is considered to be enlarged. The left liver lobe (LLL) is visible caudal to the heart in the left cranioventral abdomen in the 7th to 10th ICS. The LLL extends C from the ventral lung margins to the CC junctions. O The LLL may be considered enlarged when it ex- L tends into the left cranioventral abdomen; however, O this may be present in some horses without hepatic R pathology. The margins of the LLL are often difficult to evaluate due to shadowing created by the Fig. 12. Normal ultrasonographic appearance of the left liver overlying CC junctions. In most horses, the LLL is lobe (LLL) as visualized from the left 7th ICS. Note that the LLL located superficial to the adjacent spleen; however, is hypoechoic to the adjacent spleen. Dorsal is to the right.

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Fig. 13. Rounding of the right liver lobe margins is evident in Fig. 15. A dilated bile duct adjacent to portal vein creates the this horse with hepatitis, conﬁrmed via ultrasound-guided liver “parallel channel sign” (arrows) within the right liver lobe in this biopsy. Liver margins also extended to the costochondral junc- horse with obstructive hepatolithiasis. No hepatoliths were vis- tions (not shown in this image) in most ICS, consistent with ible in the RLL; however, multiple stones were visible within the hepatomegaly. Dorsal is to the right. left liver lobe. Dorsal is to the right.

cluding horses with pyrrolizidine alkaloid toxicosis abscessation can create hypoechoic and/or hyper- F14 (Fig. 14). Horses with obstructive cholelithiasis echoic areas within the liver.12,20 The liver is the are infrequently encountered at our hospital but can most common site for abdominal C. pseudotubercu- demonstrate a “parallel channel sign” secondary to losis infection, in which single to multiple coalescing distention of the bile duct adjacent to the portal vein 12 18 hypoechoic areas can be found. Hepatic neoplasia F15 (Fig. 15). The obstructive hepatolith may not be is relatively uncommon. Affected livers often dem- visible. When present, hepatoliths can be of vari- onstrate a diffusely heterogeneous appearance, al- able echogenicity and create variable acoustic shad- though discrete metastatic masses can be seen (Fig. 21,22 owing, in contrast to that seen with urolithiasis (Fig. 17). Ultrasound-guided biopsy is often neces- F17 F16 16). Biliary or vascular inflammation or fibrosis is sary to differentiate between hepatic abscessation a nonspecific finding with many hepatic disorders and neoplasia. that creates multiple small hyperechoic parallel lines scattered diffusely throughout hepatic paren- Spleen chyma. These occasionally cast shadows, and care Splenic abnormalities generally cause nonspecific should be taken not to confuse this appearance with clinical signs such as reduced appetite, weight loss, hepatoliths. Similarly, “starry sky” pattern was re- fever, depression, and malaise.6,12,21–26 Splenic cently described in which multiple hyperechoic foci disorders may occasionally cause colic symptoms in were found throughout the renal parenchyma in some horses, as neoplastic invasion of splenic tissue horses with granulomas. These regions showed and other disorders can produce abdominal pain. variable shadowing and were differentiated from It is rare for clinical features to direct a clinician to hepatoliths by their extrabiliary location.19 Hepatic

C C O O L L O O R R Fig. 16. Two large hepatoliths within a markedly distended bile Fig. 14. Lack of ﬁne vascular markings is evident within the duct in the right liver lobe of a 19-year-old Thoroughbred mare right liver lobe (RLL) in this horse with pyrrolizidine alkaloid with weight loss and mild depression. Note the weak shadows toxicosis conﬁrmed via ultrasound-guided biopsy. Note the created by each hepatolith. Multiple similar-appearing hepato- dense appearance of the RLL, which appears similar to splenic liths were seen throughout both liver lobes. This image was echotexture. LC indicates large colon. Dorsal is to the right. obtained from the right 8th ICS. Dorsal is to the right.

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C O C L O O L R O R Fig. 17. A single metastatic mass (arrows) within the right liver lobe of a 28-year-old Quarter Horse mare with chronic diarrhea Fig. 19. Diffuse effacement of splenic parenchyma by heteroge- and reduced appetite. Ultrasound-guided biopsy of this lesion neous tissue (arrows) in a 13-year-old Quarter Horse gelding with conﬁrmed adenocarcinoma. The entire wall of the large colon B-cell lymphoma conﬁrmed by ultrasound-guided biopsy. Nor- (bracket) was severely thickened throughout the abdomen, as mal-appearing splenic tissue is present dorsal to the lymphoma- seen deep to the RLL in this image. Dorsal is to the right. tous spleen (arrowheads). Dorsal is to the right.

implicate the spleen as the source of clinical signs, tutions. Lymphoma is the most common splenic with the exception of palpable splenic enlargement tumor in horses. Horses with splenic lymphoma during rectal examination. Therefore, most splenic often have an enlarged spleen and show diffuse in- abnormalities are identified during a complete ab- filtration of splenic tissue with heterogeneous tissue 1,2,21 dominal ultrasound exam. of mixed echogenicity (Fig. 19). Discrete F19 The spleen is the predominant feature of the left masses may also be seen.5,6 Other tumor types abdomen and is visible throughout most left ICS, the have been reported, including squamous cell carci- PLF region, and left ventral abdomen. The spleen noma, melanoma, and hemangiosarcoma,5,22,25 but often extends to or slightly to the right of ventral cannot be differentiated by their ultrasonographic midline in normal horses. Splenomegaly is difficult appearance alone (Fig. 20). Interventional proce- F20 to objectively document because the normal spleen dures such as biopsy or aspirate are required to may show rightward displacement in horses with differentiate between tumor types and to rule out gastric distention or colon displacements. The infectious or inflammatory causes. spleen is the most echogenic of the three abdominal Horses presenting with hemoabdomen should be organs and should show an evenly homogeneous carefully evaluated for evidence of splenic hema- 23,24 F18 echogenicity (Fig. 18). The spleen appears less vas- toma and/or splenic fracture. Splenic hemato- cular than the liver, although the splenic vein is mas can appear as small to large, irregularly shaped typically visible adjacent to the stomach. hypoechoic areas, similar to other disorders such as The spleen is the least commonly affected abdom- splenic abscessation or even neoplasia. Careful inal organ in horses; however, splenic neoplasia is encountered with some frequency at referral insti-

C C O O L L O O R R Fig. 20. One of several splenic masses (arrows) in a horse with Fig. 18. Transcutaneous image of the normal spleen reveals a disseminated hemangiosarcoma. Additional intrasplenic and diffusely homogeneous echogenicity. The splenic vein is visible extrasplenic masses were found throughout the abdomen and adjacent to the greater curvature of the stomach. Dorsal is to showed a highly variable ultrasonographic appearance. Dorsal the right. is to the right.

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Fig. 21. An irregularly shaped hypoechoic area (arrow) within Fig. 22. Ultrasonographic diagnosis of an intrasplenic wire (ar- the spleen of a horse with internal Corynebacterium pseudotuber- rows) and associated abscess involving the cranial portion of the culosis infection, confirmed via ultrasound-guided aspiration and spleen near the stomach. The abscess is visualized as a nearly culture. Multiple hypoechoic areas were seen throughout the anechoic area surrounding the wire tip (arrow, right im- spleen. Note the lack of encapsulation in this abscess. Dorsal age). The wire was confirmed via abdominal radiography, and is to the right. ultrasound-guided aspiration of the abscess yielded mixed growth, including two strains of Escherichia coli. Dorsal is to the right. consideration of the complete clinical picture is important to prioritize differentials. Hypoechoic areas may also be seen in horses with splenic they are expensive and do not necessarily guarantee abscessation caused by C. pseudotuberculosis (Fig. needle visibility. Free-hand ultrasound-guided 12,23 F21 21) or other infectious agents. Similar to he- techniques can be mastered with practice and pro- patic C. pseudotuberculosis abscessation, splenic ab- vide the ultrasonographer with the most flexibility scesses often lack a visible capsule. This can create throughout the procedure. The use of anatomic confusion for less experienced imagers who often landmarks as the sole means to collect samples from expect to see a well-defined capsule in horses with abdominal organs should not be used. Such tech- abscessation. Ultrasound-guided aspiration is niques place the horse at increased risk for penetra- highly useful for pathogen identification and selection of bowel or neighboring structures due to tion of appropriate antimicrobial therapy. Ultra- significant variability in the location and thickness sonographic resolution of splenic abscesses appears of abdominal organs. Ultrasound-guided sampling to be more prolonged in our experience (3 to 4 is generally considered the standard of care at refer- months in some horses), compared with liver and ral institutions. renal abscesses. Migrating foreign bodies such as Biopsies and aspirates of the liver, kidneys, and ingested wires may also cause splenic abscessation spleen are performed at our hospital on a routine F22 (Fig. 22). The presence of hyperechoic gas echoes basis to differentiate between various infectious, in- within splenic abscesses should heighten suspicion flammatory, and neoplastic pathologies that may for wire migration, especially when located in close appear similarly on ultrasound examinations.29 proximity to the stomach. Abdominal radiographs Clotting profiles are often obtained before sampling are indicated to either confirm or identify a wire as to reduce the risk of postprocedural hemorrhage, the source of abscessation. although this has been infrequently reported in horses.29,30 All procedures are performed using Ultrasound-Guided Procedures sterile technique, including sterile skin preparation As stated earlier, dramatic ultrasonographic abnor- and sterile gloving of the transducer’s and ultra- malities may be present in horses without blood sonographer’s hands. The ideal site for biopsy or work abnormalities specific to that organ.12 The aspirate is identified that will maximize acquisition converse may also be true.27,28 In either case, ul- of a diagnostic sample while avoiding vital struc- trasound-guided biopsy should be performed in tures. This varies from horse to horse and depends horses with a high index of suspicion for hepatic, on the location of visible pathology. Wite-Out® is renal, or splenic disease regardless of the source of useful to mark the skin surface to aid in re-identifi- information (clinical, hematologic, or ultrasono- cation of the intended collection site after skin prep- graphic). Ultrasound guidance allows accurate aration. A skin block is used in the majority of needle placement into affected regions and increases cases. The most important aspect of sampling is for the likelihood of a diagnostic sample. It also pre- the needle to remain within the ultrasound beam vents inadvertent entry into major blood vessels and from skin to target. This is best accomplished abdominal viscera compared with blind sampling when the ultrasonographer guides both the trans- techniques. Automatic biopsy instruments are ducer and the biopsy instrument (Fig. 23, A and B). F23 preferable. Biopsy needle guides may be used, but It is equally important to consider the “throw” of the

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Fig. 23. A, Sterile technique to obtain a splenic biopsy. After sterile skin preparation, the transducer’s and ultrasonographer’s hands are sterilely gloved. Although an assistant is used to steady and ﬁre the biopsy instrument, the ultrasonographer is responsible for guiding the needle so that it remains within the ultrasound beam (B) to guarantee needle visibility. C, The needle (arrowheads) is visible near the hypoechoic splenic nodule (arrows) but is positioned to account for the 2-cm “throw” of the needle so that the nodule is sampled (D) while simultaneously preventing sampling of the nearby left kidney (LK).

needle so that adjacent structures are not inadver- 3. Mair TS, Taylor FG, Pinsent PJ. Fever of unknown origin in tently penetrated by the biopsy needle during sam- the horse: a review of 63 cases. Equine Vet J 1989;21:260– ple acquisition (Fig. 23, C and D). We generally 265. 4. Mair TS, Hillyer MH. Chronic colic in the mature horse. collect two biopsy samples and submit one for histo- Equine Vet J 1997;29:415–420. pathologic analysis and one for culture and sensitiv- 5. East LM, Savage CJ. Abdominal neoplasia (excluding uro- ity. Culture and sensitivity results should be used genital tract). Vet Clin North Am Equine Pract 1998;14: to guide antimicrobial selection. 475–493. 6. East LM, Savage CJ, Traub-Dargatz JL. Weight loss in the 2. Summary horse: a focus on abdominal neoplasia. Equine Vet Educ 1999;11:174–178. Abdominal ultrasound has been extremely reward- 7. Divers TJ, Yeager AE. The value of ultrasonographic exam- ing at our hospital to assist in the diagnosis of mul- ination in the diagnosis and management of renal diseases in tiple disorders of abdominal organs and the horses. Equine Vet Educ 1995;7:334–341. gastrointestinal tract, covered in the previous ses- 8. Schott HC. Hematuria. In: Robinson NE, editor. Current sions. In some horses, abnormalities are straight- Therapy in Equine Medicine, 4. Philadelphia: WB Saunders forward and readily detectable by veterinarians Company; 1997:489–491. 9. Kisthardt KK, Schumacher J, Finn-Bodner ST, et al. Severe with some abdominal ultrasound experience, renal hemorrhage caused by pyelonephritis in 7 hors- whereas other disorders produce more subtle ﬁnd- es: clinical and ultrasonographic evaluation. Can Vet J ings and require the trained eye of a veteran ultra- 1999;40:571–576. sonographer well versed in the nuances of 10. Schumacher J, Schumacher J, Schmitz D. Macroscopic he- abdominal imaging. In either situation, the use of maturia of horses. Equine Vet Educ 2002;14:201–210. 11. Ehnen SJ, Divers TJ, Gillette D, et al. Obstructive nephro- ultrasound has transformed how we diagnose, treat, lithiasis and ureterolithiasis associated with chronic renal and manage horses that present with a wide variety failure in horses: eight cases (1981–1987). J Am Vet Med of clinical signs. Assoc 1990;197:249–253. 12. Pratt SM, Spier SJ, Carroll SP, et al. Evaluation of clinical References characteristics, diagnostic test results, and outcome in horses 1. Reef VB. Adult abdominal ultrasonography. In: Reef VB, with internal infection caused by Corynebacterium pseudotu- editor. Equine Diagnostic Ultrasound. Philadelphia: WB berculosis: 30 cases (1995–2003). J Am Vet Med Assoc Saunders Company; 1998:273–363. 2005;227:441–448. 2. Reimer JM. The abdomen. In: Reimer JM, editor. Atlas of 13. Draper AC, Bowen IM, Hallowell GD. Reference ranges and Equine Ultrasonography. St Louis: Mosby; 1998:224–242. reliability of transabdominal ultrasonographic renal dimen-

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sions in Thoroughbred horses. Vet Radiol Ultrasound. De- erally cryptorchid horse. J Am Vet Med Assoc 2003;222: cember 15, 2011 [Epub ahead of print]. 486–490. 14. Wise LN, Bryan JN, Sellon DC, et al. A retrospective anal- 23. Spier S, Carlson GP, Nyland TG, et al. Splenic hematoma ysis of renal carcinoma in the horse. J Vet Intern Med 2009; and abscess as a cause of chronic weight loss in a 23:913–918. horse. J Am Vet Med Assoc 1986;189:557–559. 15. Hilton HG, Aleman M, Maher O, et al. Hand-assisted lapa- 24. McGorum BC, Young LE, Milne EM. Nonfatal subcapsular roscopic nephrectomy in a standing horse for the management splenic haematoma in a horse. Equine Vet J 1996;28:166– of renal cell carcinoma. Equine Vet. Educ 2008;20 239–244. 168. 16. Diaz OS, Smith G, Reef VB. Ultrasonographic appearance 25. Southwood LL, Schott HC 2nd, Henry CJ, et al. Dissemi- of the lower urinary tract in fifteen normal horses. Vet Ra- nated hemangiosarcoma in the horse: 35 cases. J Vet In- diol Ultrasound 2007;48:560–564. tern Med 2000;14:105–109. 17. Peek SF, Divers TJ. Medical treatment of cholangiohepati- 26. Conwell RC, Hillyer MH, Mair TS, et al. Haemoperitoneum tis and cholelithiasis in mature horses: 9 cases (1991–1998). in horses: a retrospective review of 54 cases. Vet Rec 2010; Equine Vet J 2000;32:301–306. 167:514–518. 18. Reef VB, Johnston JK, Divers TJ, et al. Ultrasonographic 27. Durham AE, Smith KC, Newton JR. An evaluation of diag- findings in horses with cholelithiasis: eight cases (1985– 1987). J Am Vet Med Assoc 1990;196:1836–1840. nostic data in comparison to the results of liver biopsies in 19. Carlson KL, Chaffin MK, Corapi WV, et al. Starry sky he- mature horses. Equine Vet J 2003;35:554. patic ultrasonographic pattern in horses. Vet Radiol Ultra- 28. Durham AE, Newton JR, Smith KC, et al. Retrospective sound 2011;52:568–572. analysis of historical, clinical, ultrasonographic, serum bio- 20. Sellon DC, Spaulding K, Breuhaus BA, et al. Hepatic ab- chemical and haematological data in prognostic evaluation of scesses in three horses. J Am Vet Med Assoc 2000;216:882– equine liver disease. Equine Vet J 2003;35:542–547. 887. 29. Vaughan B, Whitcomb MB, Maher O. How to improve accu- 21. Chaffin MK, Schmitz DG, Brumbaugh GW, et al. Ultrasono- racy of ultrasound-guided procedures, in Proceedings,Am graphic characteristics of splenic and hepatic lymphosarcoma Assoc Equine Pract 2009;55:438–448. in three horses. J Am Vet Med Assoc 1992;201:743–747. 30. Tyner GA, Nolen-Walston RD, Hall T, et al. A multicenter 22. Pratt SM, Stacy BA, Whitcomb MB, et al. Malignant Ser- retrospective study of 151 renal biopsies in horses. J Vet toli cell tumor in the retained abdominal testis of a unilat- Intern Med 2011;25:532–539.

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Orig. Op. OPERATOR: Session PROOF: PE’s: AA’s: 4/Color Figure(s) ARTNO: 1st disk, 2nd beb spencers 12 1-23 3280