Single Extrahepatic Portosystemic Shunt in 3 Dogs: CT Findings and Progress

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Single Extrahepatic Portosystemic Shunt in 3 Dogs: CT Findings and Progress

Hee-Chun Lee, Chang-Moo Ji, Jong-Hyun Moon, Kyu-Woan Cho, Young-Ki Kim, Byeong-Teck Kang* and Dong-In Jung¹

Research Institute of Life Sciences, Gyeongsang National University, Jinju 660-701, Korea

*Laboratory of Veterinary Dermatology and Neurology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk 361-763, Korea

(Accepted: December 16, 2012)

Abstract : Two Maltese (2-year-old, intact female and 4-month-old, intact female) and a Pekingese (10-year-old, intact male) dogs were referred due to vomiting, anorexia, head-pressing and hypersalivation. Physical examinations, complete blood count, serum chemical analysis, radiography, ultrasonography and computed tomography (CT) were evaluated.

Laboratory findings in these dogs included high hepatic enzyme, serum bile acid and ammonia concentration.

Microhepatia was found on abdominal radiographs in two dogs. The existence of portosystemic shunt was presented in abdominal ultrasonography. The shunt vessel was identified in all dogs by CT imaging. Based on three-dimensional CT reconstruction, the origin and termination of each shunt vessel were defined certainly. In consequence, each dog was diagnosed single extrahepatic portosystemic shunt. After diagnosis, surgical treatment was performed in all dogs.

This case report describes clinical finding, imaging characteristics, and three-dimensional CT imaging of single extrahepatic portosystemic shunt cases.

Key words : single extrahepatic PSS, CT, dog.

Introduction

Portosystemic shunt (PSS) is defined as abnormal vessel that diverts normal portal blood from the stomach, intestine, spleen, and pancreas to the systemic venous circulation without first passing through the hepatic sinusoids and liver parenchyma (7,10). Most shunt vessel occurs from portal vein, and also develops from splenic vein, left gastric vein, mesenteric vein, and gastroduodenal vein that form portal vein.

The PSS can be classified as intrahepatic or extrahepatic, congenital or acquired, and single or multiple. Clinical signs are associated with the origin and volume of blood bypass- ing the liver, leading to impaired hepatic function, hepatic encephalopathy, coagulopathy, chronic gastrointestinal and lower urinary tract signs, and delayed growth (2,12,13,17, 20,21). The diagnosis is achieved by clinical sings, physical examination, blood test, urinalysis, and diagnostic imaging.

Medical management of PSS is directed to minimize hepatic cellular injury and to prevent hepatic encephalopathy. Prog- nosis of PSS is fair if the shunt vessels are occluded by surgical or transvenous method.

In this case study, we described that CT is useful method to identify shunt vessel anatomy and to assess type of PSS and considered prognosis of PSS after surgical treatment.

Case

Three dogs were referred to the Gyeongsang National Uni- versity Animal Medical Center with primary complaints of vomiting, anorexia, head pressing, and hypersalivation. The clinical signs intermittently or aggressively appeared before the presentation. The age when clinical signs had developed was from 4 months to 9 years, and one dog was intact male and other two dogs were intact female (Table 1).

Complete blood counts (CBC) and serum biochemistry tests were evaluated. In CBC, there was anemia in one dog.

Serum chemistry revealed increased liver enzyme levels, and decreased total protein and albumin (Table 2).

For the differential diagnosis, pre- and postprandial bile acid tests (IDEXX SNAP, Abaxis Vetscan), radiography and abdominal ultrasonography were performed. Pre- and postprandial bile acid tests revealed increased pre- and postpran-

1Corresponding author.

E-mail: [email protected]

Table 1. Signalment of the 3 dogs with PSS Case

Number Breed Age onset Sex Clinical signs Case1 Maltese 11 months Intact femaleHead pressing,

hypersalivation Case2 Pekingese 9 years Intact male Vomiting,

anorexia Case3 Maltese 4 months Intact female Vomiting, anorexia

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dial serum bile acids and ammonia concentration (Table 3).

Thoracic radiographs were unremarkable. On abdominal radiographs, microhepatia was identified (Fig 1). The ultrasonographic examination was performed immediately after radiographic study. An abnormally dilated and tortuous vessel (arrow) was identified around medial and ventral to caudal vena cava (CVC) (Fig 2A). A mosaic color Doppler pattern was observed in the CVC as the result of flow turbulence (Fig 2B). Due to the small size of the liver, it was impossible to determine whether the shunting vessel was located inside or outside of the liver.

Dual-phase CT angiography was performed to confirm the presence of the shunt vessels, and the locations of their origin and termination. All patients had extrahepatic portosystemic shunts identified on CT.

Case 1 and case 3 shunt type, termed right gastric-caval shunt, were identified. The shunting vessels extended ven- trally, left ward, and caudally along the lesser curvature of the stomach, to insert on the CVC from left side at the level of the cranial pole of the right kidney, caudal to the liver (Fig 3 and 5). In case 1, the splenic vein inserted on the portal vein in a normal location. But in case 3, the splenic vein inserted on the shunting vessel.

Case 2 shunt type, termed a splenophrenic shunt, arose from the splenic vein and terminated in the CVC. The large

shunting vessel extended cranially, passing cranial to the liver along the diaphragm and inserting on the caudal vena cava from left side (Fig 4).

The portal vein cranial to the origin of the shunting vessels was consistently smaller than its diameter immediately caudal to the origin of the shunt.

Based on CT results, all cases were diagnosed single extrahepatic portosystemic shunt and treated with medical management (e.g. milk-thistle fruit extract, biphenyl dimethyl di- carboxylate, ursodesoxycholic acid, and lactulose) and dietary restriction. After medical treatment, the operation was performed. An ameroid ring constrictor was placed around the shunt vessel near CVC to attenuate the abnormal vessel in all dogs. After attenuation, all dogs were rechecked. There were no clinical sings that had been chief complaints. Also, pre- and postprandial bile acid tests revealed normal bile acid and ammonia concentration, and liver enzyme value (Table 3, 4).

In one case, liver size was increased and returned to normal (case 1).

Discussion

In PSS cases, generally, the most common affected organs are the central nervous, gastrointestinal, and urinary systems (2,9,14,17,21). Clinical signs of the present patients including Table 2. Result of blood analysis in 3 dogs with PSS

Case1 Case2 Case3 Reference range WBC(× 10³/dl) 13.7 28.1 14.1 6.0-17.0

RBC(× 10⁶/dl) 7.18 ■ 4.58 5.0-8.5

Hb(mg/dl) 13 ■ 10 10.0-18.0

PCV(%) 39.3 41 34.5 35.0-55.0

MCV(fl) 55.0 ■ 58.3 60.0-77.0

MCH(pg) 18.1 ■ 21.9 19.0-25.0

PLT(× 10³/dl) 228 166 166 120-600

BUN(mg/dl) 8 18 5 7-25

ALT(U/L) 582 255 754 10-118

ALP(U/L) 126 215 773 20-150

TP(g/dl) 4.6 5.7 ■ 5.4-8.2

ALB(g/dl) ■ 1.9 1.5 2.5-4.4

Table 3. Result of liver function test in 3 dogs with PSS

Case1 Case2 Case3 Reference range Bile acid (µmol/L)

Fasting > 30 > 140 65 0-25 Bile acid (µmol/L)

Postprandial > 30 - > 140 0-25

Ammonia(µg/dl) 112 142 180 0-75

GGT(U/L) - 12 35 0-7

CHOL(mg/dl) - 75 146 125-270 Fig 1. Lateral abdominal radiography of the cases with portosystemic shunt. The axis of the stomach are displaced cranially.

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Fig 3. CT portography of case 1; axial images (A and B), and three-dimensional (3D) images (C). A; A extra-hepatic shunt (S) originates from the portal vein (P) and extends dorsally, medial to the caudal vena cava (C). B; A shunt region between a shunt vessel and CVC is identified at the level of the cranial pole of the right kidney. C; 3D image show the accurate shape, location and direction of extrahepatic single shunt (S) connecting into CVC (C). A shunt vessel passes caudo-medially and tortuously.

Fig 2. Abdominal ultrasonographs (A; case 1, B; case3). An abnormally dilated and tortuous vessel (arrow) is identified around medial and ventral to CVC. A mosaic color Doppler pattern is observed in the CVC as the result of flow turbulence.

Fig 4. CT portography of case 2; axial images (A and B), and three-dimensional (3D) images (C). A; A extra-hepatic shunt vessel (S) is located medial to the caudal vena cava (C). B; A shunt region between a shunt vessel and CVC is identified cranial to the river and caudal to the diaphragm. C; 3D image show the accurate shape, location and direction of extrahepatic single shunt (S) connecting into CVC (C).

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head pressing and hypersalivation (case 1), and vomiting and anorexia (case 2, 3) were similar with previous report (21).

According to the previous report (3), measurement of bile acid concentration was found to be the most sensitive test for the detecting of PSS. Bile acid concentration could be sensitive in detecting PSS as blood ammonia concentration (3,19).

Also, many cases, in previous studies, revealed subnormal blood urea concentration, mild to moderate increased ALT and ALP, decreased total serum protein and albumin concentration, and mild anemia (4,19). In all three cases, increased bile acid (fasting and 2-hour postprandial) and ammonia concen-

tration were detected. Serum biochemistry results were similar to previous studies as well (20).

Abdominal radiography, ultrasonography, CT, and mag- netic resonance imaging (MRI) are used generally for identi- fying shunt vessel in PSS cases. Especially, CT is frequently used to diagnose PSS due to noninvasive and brief method, and comparatively exact consequence (6). In addition, three- dimensional CT imaging precisely shows location, shape, number, and direction of shunt vessel and is helpful for final confirmation of PSS (12).

Extrahepatic portosystemic shunts are often described as porto-azygos or porto-caval, without a detailed description of exact shunt location or morphology. But according to recent study, the most common extrahepatic portosystemic shunt conformations have the six general types: 1. splenocaval shunt.

2. splenophrenic shunt, 3. splenoazygos shunt, 4. right gastric-azygos shunt with a caudal loop, 5. right gastric-caval shunt, and 6. right gastric caval shunt with a caudal loop.

Based on anatomic definition of the veins associated with the shunt origin and insertion, the first and third cases in this report were diagnosed with a right gastric-caval shunt, and second case was identified with a splenophrenic shunt.

Fig 5. CT portography of case 3; axial images (A and B), and three-dimensional (3D) images (C). A; A extra-hepatic shunt (S) originates from the portal vein (P) and extends dorsally, medial to the caudal vena cava (C). B; A shunt region between a shunt vessel and CVC is identified C; 3D image show the accurate number, shape, location and direction of shunt (S) in spite of severe tortuous direction of shunt.

This shunt is extrahepatic single shunt.

Table 4. Result of liver function test after shunt attenuation in 3 dogs with PSS

Case1 Case2 Case3 Reference range Bile acid (µmol/L)

Fasting 21 25 34 0-25

Bile acid (µmol/L)

Postprandial > 30 - > 140 0-25

Ammonia(µg/dl) - < 10 40 0-75

Fig 6. Plain radiography of the dog with portosystemic shunt of case 1; Right lateral view before surgery (A), and 149 days after surgery (B). A. The axis of the stomach is displaced cranially (arrow) and the other viscera also lies more cranially than normal especially small intestine. B. Gastric axis is parallel to 11th rib and caudoventral margin of the liver is identified slight beyond the margin of the costal arch (arrow), and there are consistent with the normal liver size.

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The prognosis after surgical intervention for shunt closure remains unpredictable. Microhepatia is a typical finding when evaluating abdominal diagnostic imaging tests in PSS (18). When portal blood bypasses the liver, a reduced deliv- ery of portal blood flow and essential hepatotrophic factors derived from the pancreas and gastrointestinal tract to the liver results in hepatocyte atrophy, and microhepatia (7,10).

In human medicine, liver size is significantly related to prognosis for survival in patients with hepatic failure and cirrhosis, as a prognostic marker (11,15,22). Likewise, liver size might be a useful prognostic indicator in assessing the func- tional capacity of the liver in animals with advanced liver disease. Liver size in animals is routinely estimated radiography, ultrasonography, and CT. However, its accuracy is con- troversial to evaluating liver size by ultrasonography (1,5,8, 16), and there is the possibility of risk of anesthesia in CT in spite of useful measurement of response to therapy in evaluation of liver volume. Liver size is easily identified by assessing the position of the caudal edges of liver with regard to the costal arch, liver extension from the diaphragm and the axis of the stomach in radiography (16). In this case report, small liver size returned to normal size after surgical intervention in case 1 (Fig 6). This case report well represents hematologic and diagnostic imaging findings with three dogs with single extrahepatic portosystemic shunt. Three-dimensional CT imaging is greatly valuable method to identify the type of PSS and anatomy of extrahepatic vasculature and confirm the diagnosis. Also, liver size check by radiography might be clinically meaningful for prognosis assessment of shunt intervention in animals with PSS.

Acknowledgements

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012-0003224).

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3마리의 개에서 발생한 단일 간외성 문맥전신 단락 증례

이희천·지창무·문종현·조규완·김영기·강병택*·정동인¹

경상대학교 생명과학연구원, *충북대학교 수의과대학

요 약 : 두 마리의 말티즈견 (2살 중성화 암컷, 4개월 암컷)과 한 마리의 페키니즈견 (10살 수컷)이 구토, 식욕부진, 두위하강과 침흘림 등의 증상으로 내원하였다. 신체검사, 혈액검사, 방사선검사, 초음파, 컴퓨터단층촬영이 진단을 위 해 실시되었다. 실험실 검사에서 높은 간수치, 담즙산 수치, 암모니아 농도가 세 마리 모두에서 확인되었다. 두 마리의 환축에서 방사선검사 상 소간증이 확인되었다.복부 초음파 검사에서 세 마리 모두 문맥전신 단락이 많이 의심되어 컴 퓨터단층촬영을 실시하였고, 그 결과 모두 단일 간외성 문맥전신 단락으로 확인되었다. 진단 후 세마리는 모두 수술적 인 방법을 통해 단락 혈관에 아메로이드 링을 적용하였다. 본 증례보고는 세 마리의 개에서 발생한 단일 간외성 문맥 전신 단락 증례에 대한 임상적, 영상학적인 특징들을 잘 나타내고 있으며, 컴퓨터단층촬영이 문맥전신단락의 정확한 진단을 위해 유용한 진단기법임을 잘 나타내고 있다.

주요어 : 단일 간외성 문맥전신단락, 컴퓨터단층촬영, 개