Ultrasound and the Nonacute Abdomen: The Abdominal Organs · Ultrasound and the Nonacute Abdomen:...

Ultrasound and the Nonacute Abdomen: TheAbdominal 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 andincreased availability of skilled equine ultrasonologists. As our knowledge base continues to grow,increased awareness is important for owners and veterinarians to understand the diagnostic potentialof abdominal ultrasound. Evaluation of abdominal organs is best performed as part of a completeabdominal ultrasound exam. Ultrasound-guided procedures are often required to differentiate be-tween various infectious, inflammatory, and neoplastic disorders. Author’s address: Clinical LargeAnimal Ultrasound, Department of Surgical and Radiological Sciences, University of California, OneShields Avenue, Davis, CA 95616; e-mail: [email protected]. © 2012 AAEP.

1. Introduction

Evaluation of the abdominal organs, including thekidneys, liver, and spleen, is generally performed aspart of a complete ultrasound examination in non-acute patients.1 Many horses with hepatic, renal,or splenic abnormalities present with nonspecificclinical signs3–6 similar to those in horses with gas-trointestinal tract disorders. Complete blood count(CBC) and serum chemistry analysis may be unre-markable or show only evidence of inflammationsuch as hyperfibrinogenemia and hyperglobuline-mia. Subsequently, a full exam is required to max-imize diagnostic yield in many cases. In otherhorses, clinical exam findings and serum biochemis-try analysis may indicate primary renal or hepaticdisease, in which case the examiner may choose tofocus on the urinary tract or liver, respectively.Although horses with abdominal organ disorders in-frequently present as acute colic patients, cursoryexamination of abdominal organs can yield importantinformation during routine colic ultrasound exams.

Admittedly, mastery of abdominal ultrasound re-quires experience and patience, much more so thanbasic ultrasound of the acute abdomen. Similar toany anatomic region, however, cursory examinationis possible by a motivated practitioner equippedwith appropriate ultrasound equipment. It isequally important for field practitioners to under-stand our increased ability to diagnose and treatdisorders of abdominal organs in the referral set-ting. Ultrasound findings often help guide treat-ment planning, including the need for medicaltherapy or surgical intervention. Not only do wegain valuable information about the appearance ofabdominal organs, ultrasound-guided biopsy and/oraspirate can be used to determine the underlyingetiology, to establish an appropriate treatment plan,and for prognostication.1–2

Ultrasonographic Technique

A low-frequency (2–5 MHz) curvilinear transducer isnecessary to evaluate abdominal organs in the adult

28 2012 � Vol. 58 � AAEP PROCEEDINGS

IN-DEPTH: ULTRASOUND OF THE THORAX AND ABDOMEN

NOTES

Orig. Op. OPERATOR: Session PROOF: PE’s: AA’s: 4/Color Figure(s) ARTNO:

1st disk, 2nd beb spencers 12 1-23 3280

horse due to their deep location (15 to 30 cm) relativeto the skin surface. This transducer is available formost of today’s ultrasound machines, the majority ofwhich are able to obtain exceptionally high-qualityabdominal images. In contrast, a rectal transducercan only penetrate to 5 to 10 cm, which is insuffi-cient to image the left kidney and the majority of thespleen, liver, and right kidney from the transcuta-neous window. A rectal transducer can be used toimage the caudal portion of the left kidney andspleen during transrectal examination.

For the highest quality images, the entire abdo-men should be clipped with #40 blades, especially inolder, obese, or thick-coated horses that tend to im-age poorly (Fig. 1). Alcohol saturation can producediagnostic quality images, but the subtle nature ofmany ultrasonographic findings in the nonacute ab-domen may not be detectable without clipping.After clipping, the skin should be cleaned with a wetsponge to remove dirt and debris, and ultrasound gelis then applied.

A systematic approach to each exam is importantfor consistency and to improve diagnostic yield.At the University of California, Davis (UC Davis),the entire abdomen is evaluated in the majority ofnonacute patients presenting to the Large AnimalUltrasound Service. Each side of the abdomen isdivided into three regions: (1) paralumbar fossa/flank region (PLF); (2) 5th through 17th intercostalspaces (ICS) from the ventral lung margins to thecostochondral junctions; and (3) ventral abdomenfrom the sternum to the inguinal region. The examshould be performed in the same manner, regardlessof clinical suspicion of cause. Structures evaluatedfrom the right side of the abdomen include the ce-cum and cecal mesentery, right kidney, right liverlobe, duodenum, and right dorsal colon. The rightventral colon is primarily visualized from the right

ventral abdomen. Structures evaluated from theleft side of the abdomen include the left kidney,spleen, stomach, and left liver lobe. The left dorsaland ventral colons are seen predominantly from theleft ventral abdomen.

Scanning depth should be adjusted frequentlyduring the exam to best image the superficial anddeep parenchyma of each organ. No single depthsetting is appropriate for all abdominal organ imag-ing. An abdominal program or preset should beselected to maximize abdominal detail. Time-gaincompensation controls should also be adjusted fordeep cavity imaging (Fig. 2).

Renal and Urinary Tract UltrasoundSpecific indications for renal ultrasound includeazotemia, hematuria, pollakiuria, dysuria, or abnor-mal findings of cystoliths, ureteroliths, or left renalenlargement on rectal palpation.7–11 It is impor-tant to remember that horses with significant renalabnormalities may present with a normal CBC andserum biochemical profile.12

The left kidney is visible transcutaneously andtransrectally. Transcutaneously, the left kidney islocated deep to the spleen in the left PLF region andthe left 15th to 17th ICS at a scanning depth of 20 to30 cm (Fig. 3). The best images are often obtainedin the left 16th to 17th ICS; however, the kidneyshould be imaged from all possible windows. AtUC Davis, we routinely use a “special” technique toimage the left kidney that entails placing the trans-ducer caudal to the last rib, midway between thetuber coxae and stifle, and aiming in a dorsocranialdirection. By applying gradual force with each ex-piration, the transducer is effectively brought closerto the left kidney and a superior image obtainedthan with traditional techniques. Transrectally,

Fig. 1. Region to be clipped for complete abdominal ultra-sound. The left abdomen is clipped in similar fashion. Fig. 2. Time-gain compensation controls adjusted properly for

deep cavity imaging.

AAEP PROCEEDINGS � Vol. 58 � 2012 29


F1

COLOR

F2

F3

COLOR



the left kidney is typically visible at arm’s length;however, only the caudal portion of the kidney canbe seen. The right kidney is seen dorsally in theright 15th to 17th ICS at a more superficial scanningdepth of 15 to 20 cm, compared with the left kidney.The right kidney cannot be imaged transrectally inmost horses.

Renal ultrasonographic parameters include size,shape, cortical echogenicity (hypoechoic to the adja-cent spleen), cortical thickness, medullary echoge-nicity (hypoechoic to the cortex), andcorticomedullary distinction. The renal pelvisshould be evaluated for the presence of nephrolithsand dilation (pyelectasia). Reported renal sizemeasurements are somewhat variable, and horsesize should be considered when interpreting mea-surements. In our experience, normal adult kid-neys range from 5 to 9 cm in width and 15 to 19 cmin length; however, a recent study reported smallermeasurements than that described by Reef and thatof our own clinical experience.1,13

Small kidneys are generally associated withchronic renal failure.7 Affected kidneys often showa distorted shape, increased cortical echogenicityand thickness, and poor corticomedullary distinctionand may have nephrolith(s) or peripelvic mineral-ization. Some are nearly unrecognizable as kid-neys (Fig. 4). In some horses with chronic renalfailure, one kidney may appear to be end-stage andnonfunctional, with the contralateral kidney show-ing enlargement but relatively normal renalparenchyma.7

Enlarged kidneys with or without increased corti-cal echogenicity and thickness may be secondary toacute renal failure, urolithiasis, nephritis, pyelone-phritis, hydronephrosis, abscessation, or, less com-monly, neoplasia.1,7,9–12 Interventional proceduressuch as ultrasound-guided biopsy or aspirate areoften necessary to differentiate between potentialdiagnoses. Horses with acute renal failure mayhave perirenal edema, seen as an anechoic fluidlayer between the renal capsule and cortex (Fig. 5).

Renal parenchyma is seldom distorted in horseswith acute renal failure; however, a clearly visibleand discrete corticomedullary junction is often pres-ent. Renal abscesses have been reported and ap-pear as variably shaped hypoechoic or hyperechoicareas within the renal cortex and/or medulla.12

The kidneys are the second most common abdominalorgan to be affected in horses with internal Coryne-bacterium pseudotuberculosis infection. Careshould be taken not to misinterpret the hypoechoicarea visible in the deep medullary portion of theright kidney for a mass or abscess. Hematuria isnot uncommon in horses with renal abscessation.Renal neoplasia is relatively uncommon in horsesbut may be encountered with some regularity atreferral hospitals. Renal adenocarcinoma is themost common primary tumor, producing largemasses that completely efface renal parenchyma(Fig. 6).14,15 Renal mestastasis of other tumortypes has also been reported.1

Fig. 3. Normal appearance of the left kidney (LK) as seen fromthe left 16th ICS. The renal cortex is hypoechoic to the adjacentspleen and a clear corticomedullary junction is visible. Dorsal isto the right.

Fig. 4. Ultrasonographic appearance of an end-stage left kidneyin a horse with chronic renal failure. The kidney is small andshows large hyperechoic areas consistent with fibrosis, scarring,nephrolithiasis, or mineralization. Renal parenchyma is nearlyunrecognizable. Dorsal is to the right.

Fig. 5. Perirenal edema (arrows) in a 4-day-old foal with acuterenal failure. Note the distinct corticomedullary junction that isoften noted in horses with acute renal failure. Dorsal is to theright.



F4

F5

COLOR

F6

COLOR

COLOR



Horses with urolithiasis can present with hema-turia after exercise, azotemia, and occasionally withsigns of colic.8,10,11 Urolithiasis is regularly en-countered by clinicians at our hospital. Nephro-liths are easily recognized as hyperechoic structureswithin the renal pelvis that cast hard shadows (Fig.7). Renal sludge appears similarly but may pro-duce a “dirty” or less distinct shadow. Differentia-tion between nephroliths and renal sludge is notstraightforward. Care should be taken not to mis-interpret the hyperechoic appearance of the renalpelvis as nephrolithiasis. All horses with urolithi-asis should undergo transcutaneous evaluation ofboth kidneys and transrectal evaluation of the en-tire urinary tract to rule out additional uroliths andfor evidence of underlying renal disease. Transrec-tal evaluation of the bladder and ureters is alsoindicated in horses with distention of the renal pel-vis because a downstream cystolith (Fig. 8) or uret-erolith may be the cause for renal pyelectasia.Using a transrectal approach, the left and right ure-

ters are evaluated individually (Fig. 9), beginning atthe bladder trigone and following each as far crani-ally as possible. The left ureter can regularly befollowed along its length to the left kidney. Themajority of the right ureter is also visible; however,the ureteropelvic junction with the right kidney israrely visible in normal or abnormal horses. Thepresence of ureteral motility is helpful to differenti-ate ureters from blood vessels and the vas deferensin male horses. The normal appearance of the cau-dal ureters has been described.16 Ureteroliths canbe identified along the length of the ureter (Fig. 10).In the author’s experience, urolithiasis is often as-sociated with ureteral wall thickening regardless ofthe location of the stone. Most importantly, incases of urolithiasis, the examiner should be re-minded to perform bladder endoscopy after ultra-sound examination. Gas that is introduced duringendoscopy will obscure ultrasonographic visualiza-tion of urinary structures, and its hyperechoic ap-pearance can be easily confused with uroliths.

Idiopathic renal hematuria should be a differen-tial in horses with a large amount of frank blood intheir urine.8,10 Affected kidneys show distention ofthe renal pelvis with echogenic material consistentwith hemorrhage and clot formation. Renal archi-

Fig. 6. Renal enlargement and diffuse effacement of renal pa-renchyma in a horse with renal adenocarcinoma of the left kid-ney, visualized from the left paralumbar fossa region. Dorsal isto the right.

Fig. 7. Large nephrolith within the renal pelvis of the left kid-ney, visible from the left paralumbar fossa region, in a horse thatpresented for pollakiuria and microscopic hematuria due to abladder stone. The horse had a previous bladder stone removed3 years earlier, at which time nephroliths were also noted. Dor-sal is to the right.

Fig. 8. Transrectal image of a large cystolith (arrow) within theurinary bladder of a 20-year-old Arabian gelding with hematuria.

Fig. 9. Normal transrectal image of the midportion of the rightureter.



F7

F8

COLOR

COLOR

F9

F10

COLOR

COLOR



tecture is often otherwise unremarkable. Horsesare typically unilaterally affected. Removal of theaffected kidney has not been reported to be effectivebecause the contralateral kidney may subsequentlybecome affected. Biopsy has not been rewarding inhorses to reveal the underlying cause of idiopathicrenal hematuria.

Renal cysts may be identified as an incidentalfinding in normal horses. In such cases, a singularcyst is typically present. Multiple small corticalcysts may be found in horses with acute or chronicrenal failure.

LiverThe liver is generally evaluated as part of a completeabdominal ultrasound but may be the primary focusin horses with elevated hepatic enzymes. Similarto horses with renal disease, horses with significanthepatic abnormalities may have normal hepatic en-zymes.12 In such cases, clinicians should resist thetemptation to dismiss abnormal hepatic ultrasoundfindings as a potential cause of clinical signs. Bi-opsy may prove useful to document the presence ofactive liver disease in such cases.

The right liver lobe (RLL) is visible ventral to thelung margins in the right 8th to 15th ICS (Fig. 11),although visibility can be quite variable withinthese ICS. The RLL should not extend to or beyondthe costochondral (CC) junctions, in which case it isconsidered to be enlarged. The left liver lobe (LLL)is visible caudal to the heart in the left cranioventralabdomen in the 7th to 10th ICS. The LLL extendsfrom the ventral lung margins to the CC junctions.The LLL may be considered enlarged when it ex-tends into the left cranioventral abdomen; however,this may be present in some horses without hepaticpathology. The margins of the LLL are often diffi-cult to evaluate due to shadowing created by theoverlying CC junctions. In most horses, the LLL islocated superficial to the adjacent spleen; however,

it may occasionally be positioned deep to the spleen,in which case the LLL margins will appear falselyrounded. Echogenicity of the LLL should be hy-poechoic to the adjacent spleen (Fig. 12). Scanningdepth ranges from 10 to 30 cm and should bechanged in each ICS to best evaluate the superficialand deep parenchyma of the liver.

Ultrasonographic abnormalities include hepato-megaly, rounded margins (Fig. 13), changes in echo-genicity (usually increased), decreased fine vascularmarkings, biliary/vascular fibrosis/inflammation,hepatoliths, biliary distention, and, less commonly,evidence of abscessation or neoplasia. Hepatomeg-aly and rounded margins may be seen with multipledisease processes, including hepatitis, cholangio-hepatitis, obstructive cholelithiasis, and neopla-sia.17,18 Decreased fine vascular marking (FVM) isa nonspecific but significant finding and is oftenoverlooked by less experienced imagers due to itssubtle nature. Decreased FVM causes the liver toappear dense and similar in echotexture to thespleen. It may be the only sonographic abnormal-ity in some horses with primary liver disease, in-

Fig. 10. Transrectal image of an obstructive ureterolith withinthe proximal portion of the right ureter in a 14-year-old QuarterHorse mare with persistent azotemia despite the removal of sev-eral bladder stones 5 months prior. Right renal ultrasound re-vealed severe distention of the renal pelvis with echogenicmaterial.

Fig. 11. Normal transcutaneous image of the right liver lobe(RLL) obtained from the right 13th ICS showing normal sharpmargins, echotexture, and fine vascular markings. Dorsal is tothe right.

Fig. 12. Normal ultrasonographic appearance of the left liverlobe (LLL) as visualized from the left 7th ICS. Note that the LLLis hypoechoic to the adjacent spleen. Dorsal is to the right.



F11

COLOR

F12

F13

COLOR

COLOR



cluding horses with pyrrolizidine alkaloid toxicosis(Fig. 14). Horses with obstructive cholelithiasisare infrequently encountered at our hospital but candemonstrate a “parallel channel sign” secondary todistention of the bile duct adjacent to the portal vein(Fig. 15).18 The obstructive hepatolith may not bevisible. When present, hepatoliths can be of vari-able echogenicity and create variable acoustic shad-owing, in contrast to that seen with urolithiasis (Fig.16). Biliary or vascular inflammation or fibrosis isa nonspecific finding with many hepatic disordersthat creates multiple small hyperechoic parallellines scattered diffusely throughout hepatic paren-chyma. These occasionally cast shadows, and careshould be taken not to confuse this appearance withhepatoliths. Similarly, “starry sky” pattern was re-cently described in which multiple hyperechoic fociwere found throughout the renal parenchyma inhorses with granulomas. These regions showedvariable shadowing and were differentiated fromhepatoliths by their extrabiliary location.19 Hepatic

abscessation can create hypoechoic and/or hyper-echoic areas within the liver.12,20 The liver is themost common site for abdominal C. pseudotubercu-losis infection, in which single to multiple coalescinghypoechoic areas can be found.12 Hepatic neoplasiais relatively uncommon. Affected livers often dem-onstrate a diffusely heterogeneous appearance, al-though discrete metastatic masses can be seen (Fig.17).21,22 Ultrasound-guided biopsy is often neces-sary to differentiate between hepatic abscessationand neoplasia.

SpleenSplenic abnormalities generally cause nonspecificclinical signs such as reduced appetite, weight loss,fever, depression, and malaise.6,12,21–26 Splenicdisorders may occasionally cause colic symptoms insome horses, as neoplastic invasion of splenic tissueand other disorders can produce abdominal pain.It is rare for clinical features to direct a clinician to

Fig. 13. Rounding of the right liver lobe margins is evident inthis horse with hepatitis, confirmed via ultrasound-guided liverbiopsy. Liver margins also extended to the costochondral junc-tions (not shown in this image) in most ICS, consistent withhepatomegaly. Dorsal is to the right.

Fig. 14. Lack of fine vascular markings is evident within theright liver lobe (RLL) in this horse with pyrrolizidine alkaloidtoxicosis confirmed via ultrasound-guided biopsy. Note thedense appearance of the RLL, which appears similar to splenicechotexture. LC indicates large colon. Dorsal is to the right.

Fig. 15. A dilated bile duct adjacent to portal vein creates the“parallel channel sign” (arrows) within the right liver lobe in thishorse with obstructive hepatolithiasis. No hepatoliths were vis-ible in the RLL; however, multiple stones were visible within theleft liver lobe. Dorsal is to the right.

Fig. 16. Two large hepatoliths within a markedly distended bileduct in the right liver lobe of a 19-year-old Thoroughbred marewith weight loss and mild depression. Note the weak shadowscreated by each hepatolith. Multiple similar-appearing hepato-liths were seen throughout both liver lobes. This image wasobtained from the right 8th ICS. Dorsal is to the right.



F14

F15

F16

COLOR

COLOR

F17

COLOR

COLOR



implicate the spleen as the source of clinical signs,with the exception of palpable splenic enlargementduring rectal examination. Therefore, most splenicabnormalities are identified during a complete ab-dominal ultrasound exam.

The spleen is the predominant feature of the leftabdomen and is visible throughout most left ICS, thePLF region, and left ventral abdomen. The spleenoften extends to or slightly to the right of ventralmidline in normal horses. Splenomegaly is difficultto objectively document because the normal spleenmay show rightward displacement in horses withgastric distention or colon displacements. Thespleen is the most echogenic of the three abdominalorgans and should show an evenly homogeneousechogenicity (Fig. 18). The spleen appears less vas-cular than the liver, although the splenic vein istypically visible adjacent to the stomach.

The spleen is the least commonly affected abdom-inal organ in horses; however, splenic neoplasia isencountered with some frequency at referral insti-

tutions. Lymphoma is the most common splenictumor in horses. Horses with splenic lymphomaoften have an enlarged spleen and show diffuse in-filtration of splenic tissue with heterogeneous tissueof mixed echogenicity (Fig. 19).1,2,21 Discretemasses may also be seen.5,6 Other tumor typeshave been reported, including squamous cell carci-noma, melanoma, and hemangiosarcoma,5,22,25 butcannot be differentiated by their ultrasonographicappearance alone (Fig. 20). Interventional proce-dures such as biopsy or aspirate are required todifferentiate between tumor types and to rule outinfectious or inflammatory causes.

Horses presenting with hemoabdomen should becarefully evaluated for evidence of splenic hema-toma and/or splenic fracture.23,24 Splenic hemato-mas can appear as small to large, irregularly shapedhypoechoic areas, similar to other disorders such assplenic abscessation or even neoplasia. Careful

Fig. 17. A single metastatic mass (arrows) within the right liverlobe of a 28-year-old Quarter Horse mare with chronic diarrheaand reduced appetite. Ultrasound-guided biopsy of this lesionconfirmed adenocarcinoma. The entire wall of the large colon(bracket) was severely thickened throughout the abdomen, asseen deep to the RLL in this image. Dorsal is to the right.

Fig. 18. Transcutaneous image of the normal spleen reveals adiffusely homogeneous echogenicity. The splenic vein is visibleadjacent to the greater curvature of the stomach. Dorsal is tothe right.

Fig. 19. Diffuse effacement of splenic parenchyma by heteroge-neous tissue (arrows) in a 13-year-old Quarter Horse gelding withB-cell lymphoma confirmed by ultrasound-guided biopsy. Nor-mal-appearing splenic tissue is present dorsal to the lymphoma-tous spleen (arrowheads). Dorsal is to the right.

Fig. 20. One of several splenic masses (arrows) in a horse withdisseminated hemangiosarcoma. Additional intrasplenic andextrasplenic masses were found throughout the abdomen andshowed a highly variable ultrasonographic appearance. Dorsalis to the right.



F18

COLOR

COLOR

F19

F20

COLOR

COLOR



consideration of the complete clinical picture is im-portant to prioritize differentials. Hypoechoic ar-eas may also be seen in horses with splenicabscessation caused by C. pseudotuberculosis (Fig.21) or other infectious agents.12,23 Similar to he-patic C. pseudotuberculosis abscessation, splenic ab-scesses often lack a visible capsule. This can createconfusion for less experienced imagers who oftenexpect to see a well-defined capsule in horses withabscessation. Ultrasound-guided aspiration ishighly useful for pathogen identification and selec-tion of appropriate antimicrobial therapy. Ultra-sonographic resolution of splenic abscesses appearsto be more prolonged in our experience (3 to 4months in some horses), compared with liver andrenal abscesses. Migrating foreign bodies such asingested wires may also cause splenic abscessation(Fig. 22). The presence of hyperechoic gas echoeswithin splenic abscesses should heighten suspicionfor wire migration, especially when located in closeproximity to the stomach. Abdominal radiographsare indicated to either confirm or identify a wire asthe source of abscessation.

Ultrasound-Guided ProceduresAs stated earlier, dramatic ultrasonographic abnor-malities may be present in horses without bloodwork abnormalities specific to that organ.12 Theconverse may also be true.27,28 In either case, ul-trasound-guided biopsy should be performed inhorses with a high index of suspicion for hepatic,renal, or splenic disease regardless of the source ofinformation (clinical, hematologic, or ultrasono-graphic). Ultrasound guidance allows accurateneedle placement into affected regions and increasesthe likelihood of a diagnostic sample. It also pre-vents inadvertent entry into major blood vessels andabdominal viscera compared with blind samplingtechniques. Automatic biopsy instruments arepreferable. Biopsy needle guides may be used, but

they are expensive and do not necessarily guaranteeneedle visibility. Free-hand ultrasound-guidedtechniques can be mastered with practice and pro-vide the ultrasonographer with the most flexibilitythroughout the procedure. The use of anatomiclandmarks as the sole means to collect samples fromabdominal organs should not be used. Such tech-niques place the horse at increased risk for penetra-tion of bowel or neighboring structures due tosignificant variability in the location and thicknessof abdominal organs. Ultrasound-guided samplingis generally considered the standard of care at refer-ral institutions.

Biopsies and aspirates of the liver, kidneys, andspleen are performed at our hospital on a routinebasis to differentiate between various infectious, in-flammatory, and neoplastic pathologies that mayappear similarly on ultrasound examinations.29

Clotting profiles are often obtained before samplingto reduce the risk of postprocedural hemorrhage,although this has been infrequently reported inhorses.29,30 All procedures are performed usingsterile technique, including sterile skin preparationand sterile gloving of the transducer’s and ultra-sonographer’s hands. The ideal site for biopsy oraspirate is identified that will maximize acquisitionof a diagnostic sample while avoiding vital struc-tures. This varies from horse to horse and dependson the location of visible pathology. Wite-Out® isuseful to mark the skin surface to aid in re-identifi-cation of the intended collection site after skin prep-aration. A skin block is used in the majority ofcases. The most important aspect of sampling is forthe needle to remain within the ultrasound beamfrom skin to target. This is best accomplishedwhen the ultrasonographer guides both the trans-ducer and the biopsy instrument (Fig. 23, A and B).It is equally important to consider the “throw” of the

Fig. 21. An irregularly shaped hypoechoic area (arrow) withinthe spleen of a horse with internal Corynebacterium pseudotuber-culosis infection, confirmed via ultrasound-guided aspiration andculture. Multiple hypoechoic areas were seen throughout thespleen. Note the lack of encapsulation in this abscess. Dorsalis to the right.

Fig. 22. Ultrasonographic diagnosis of an intrasplenic wire (ar-rows) and associated abscess involving the cranial portion of thespleen near the stomach. The abscess is visualized as a nearlyanechoic area surrounding the wire tip (arrow, right im-age). The wire was confirmed via abdominal radiography, andultrasound-guided aspiration of the abscess yielded mixedgrowth, including two strains of Escherichia coli. Dorsal is to theright.



F21

F22

COLOR

F23

COLOR



needle so that adjacent structures are not inadver-tently penetrated by the biopsy needle during sam-ple acquisition (Fig. 23, C and D). We generallycollect two biopsy samples and submit one for histo-pathologic analysis and one for culture and sensitiv-ity. Culture and sensitivity results should be usedto guide antimicrobial selection.

2. Summary

Abdominal ultrasound has been extremely reward-ing at our hospital to assist in the diagnosis of mul-tiple disorders of abdominal organs and thegastrointestinal tract, covered in the previous ses-sions. In some horses, abnormalities are straight-forward and readily detectable by veterinarianswith some abdominal ultrasound experience,whereas other disorders produce more subtle find-ings and require the trained eye of a veteran ultra-sonographer well versed in the nuances ofabdominal imaging. In either situation, the use ofultrasound has transformed how we diagnose, treat,and manage horses that present with a wide varietyof clinical signs.

References1. Reef VB. Adult abdominal ultrasonography. In: Reef VB,

editor. Equine Diagnostic Ultrasound. Philadelphia: WBSaunders Company; 1998:273–363.

2. Reimer JM. The abdomen. In: Reimer JM, editor. Atlas ofEquine Ultrasonography. St Louis: Mosby; 1998:224–242.

3. Mair TS, Taylor FG, Pinsent PJ. Fever of unknown origin inthe horse: a review of 63 cases. Equine Vet J 1989;21:260–265.

4. Mair TS, Hillyer MH. Chronic colic in the mature horse.Equine Vet J 1997;29:415–420.

5. East LM, Savage CJ. Abdominal neoplasia (excluding uro-genital tract). Vet Clin North Am Equine Pract 1998;14:475–493.

6. East LM, Savage CJ, Traub-Dargatz JL. Weight loss in thehorse: a focus on abdominal neoplasia. Equine Vet Educ1999;11:174–178.

7. Divers TJ, Yeager AE. The value of ultrasonographic exam-ination in the diagnosis and management of renal diseases inhorses. Equine Vet Educ 1995;7:334–341.

8. Schott HC. Hematuria. In: Robinson NE, editor. CurrentTherapy in Equine Medicine, 4. Philadelphia: WB SaundersCompany; 1997:489–491.

9. Kisthardt KK, Schumacher J, Finn-Bodner ST, et al. Severerenal hemorrhage caused by pyelonephritis in 7 hors-es: clinical and ultrasonographic evaluation. Can Vet J1999;40:571–576.

10. Schumacher J, Schumacher J, Schmitz D. Macroscopic he-maturia of horses. Equine Vet Educ 2002;14:201–210.

11. Ehnen SJ, Divers TJ, Gillette D, et al. Obstructive nephro-lithiasis and ureterolithiasis associated with chronic renalfailure in horses: eight cases (1981–1987). J Am Vet MedAssoc 1990;197:249–253.

12. Pratt SM, Spier SJ, Carroll SP, et al. Evaluation of clinicalcharacteristics, diagnostic test results, and outcome in horseswith internal infection caused by Corynebacterium pseudotu-berculosis: 30 cases (1995–2003). J Am Vet Med Assoc2005;227:441–448.

13. Draper AC, Bowen IM, Hallowell GD. Reference ranges andreliability of transabdominal ultrasonographic renal dimen-

Fig. 23. A, Sterile technique to obtain a splenic biopsy. After sterile skin preparation, the transducer’s and ultrasonographer’shands are sterilely gloved. Although an assistant is used to steady and fire the biopsy instrument, the ultrasonographer isresponsible 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 sothat the nodule is sampled (D) while simultaneously preventing sampling of the nearby left kidney (LK).



COLOR



sions in Thoroughbred horses. Vet Radiol Ultrasound. De-cember 15, 2011 [Epub ahead of print].

14. Wise LN, Bryan JN, Sellon DC, et al. A retrospective anal-ysis of renal carcinoma in the horse. J Vet Intern Med 2009;23:913–918.

15. Hilton HG, Aleman M, Maher O, et al. Hand-assisted lapa-roscopic nephrectomy in a standing horse for the managementof renal cell carcinoma. Equine Vet. Educ 2008;20 239–244.

16. Diaz OS, Smith G, Reef VB. Ultrasonographic appearanceof the lower urinary tract in fifteen normal horses. Vet Ra-diol Ultrasound 2007;48:560–564.

17. Peek SF, Divers TJ. Medical treatment of cholangiohepati-tis and cholelithiasis in mature horses: 9 cases (1991–1998).Equine Vet J 2000;32:301–306.

18. Reef VB, Johnston JK, Divers TJ, et al. Ultrasonographicfindings in horses with cholelithiasis: eight cases (1985–1987). J Am Vet Med Assoc 1990;196:1836–1840.

19. Carlson KL, Chaffin MK, Corapi WV, et al. Starry sky he-patic ultrasonographic pattern in horses. Vet Radiol Ultra-sound 2011;52:568–572.

20. Sellon DC, Spaulding K, Breuhaus BA, et al. Hepatic ab-scesses in three horses. J Am Vet Med Assoc 2000;216:882–887.

21. Chaffin MK, Schmitz DG, Brumbaugh GW, et al. Ultrasono-graphic characteristics of splenic and hepatic lymphosarcomain three horses. J Am Vet Med Assoc 1992;201:743–747.

22. Pratt SM, Stacy BA, Whitcomb MB, et al. Malignant Ser-toli cell tumor in the retained abdominal testis of a unilat-

erally cryptorchid horse. J Am Vet Med Assoc 2003;222:486 – 490.

23. Spier S, Carlson GP, Nyland TG, et al. Splenic hematomaand abscess as a cause of chronic weight loss in ahorse. J Am Vet Med Assoc 1986;189:557–559.

24. McGorum BC, Young LE, Milne EM. Nonfatal subcapsularsplenic haematoma in a horse. Equine Vet J 1996;28:166–168.

25. Southwood LL, Schott HC 2nd, Henry CJ, et al. Dissemi-nated hemangiosarcoma in the horse: 35 cases. J Vet In-tern Med 2000;14:105–109.

26. Conwell RC, Hillyer MH, Mair TS, et al. Haemoperitoneumin horses: a retrospective review of 54 cases. Vet Rec 2010;167:514–518.

27. Durham AE, Smith KC, Newton JR. An evaluation of diag-nostic data in comparison to the results of liver biopsies inmature horses. Equine Vet J 2003;35:554.

28. Durham AE, Newton JR, Smith KC, et al. Retrospectiveanalysis of historical, clinical, ultrasonographic, serum bio-chemical and haematological data in prognostic evaluation ofequine liver disease. Equine Vet J 2003;35:542–547.

29. Vaughan B, Whitcomb MB, Maher O. How to improve accu-racy of ultrasound-guided procedures, in Proceedings, AmAssoc Equine Pract 2009;55:438–448.

30. Tyner GA, Nolen-Walston RD, Hall T, et al. A multicenterretrospective study of 151 renal biopsies in horses. J VetIntern Med 2011;25:532–539.





Ultrasound and the Nonacute Abdomen: The Abdominal Organs · Ultrasound and the Nonacute Abdomen:...

Documents

Transcript of Ultrasound and the Nonacute Abdomen: The Abdominal Organs · Ultrasound and the Nonacute Abdomen:...