Effect of breed on anatomy of portosystemic shunts resulting from congenital diseases in dogs and cats: a review of 242 cases

OBJECTIVE: To evaluate the effect of species and breed on the anatomy of portosystemic vascular anomalies in dogs and cats. DESIGN: Retrospective study of 233 dogs and nine cats presenting to the University Veterinary Centre, Sydney. METHODS: Case records were evaluated for breed, sex, age, anatomical and histological diagnosis. Cases were included when a portosystemic vascular anomaly resulted from a congenital or developmental abnormality of the liver or portal venous system. RESULTS: Disease conditions included single congenital portosystemic shunt with patent portal vasculature (214 dogs, nine cats), portal vein aplasia (nine dogs), multiple acquired shunts resulting from portal vein hypoplasia (seven dogs), biliary atresia (one dog) and microvascular dysplasia (one dog). One Maltese had a single, congenital shunt and multiple acquired shunts resulting from hepatic cirrhosis. Breeds that were significantly over-represented included the Maltese, Silky Terrier, Australian Cattle Dog, Bichon Frise, Shih Tzu, Miniature Schnauzer, Border Collie, Jack Russell Terrier, Irish Wolfhound and Himalayan cat. Bichon Frise with shunts were significantly more likely to be female than male (12:2, P < 0.001). Two hundred and fourteen dogs (91.4%), and all cats, had shunts that were amenable to attenuation. Inoperable shunts occurred in 19 dogs (8.2%). Fifty six of 61 (92%) operable shunts in large breed dogs were intrahepatic, versus 10/153 (7%) in small breeds (P < 0.0001). Breeds that were not predisposed to portosystemic shunts were significantly more likely to have unusual or inoperable shunts than dogs from predisposed breeds (29% versus 7.6%, P < 0.0001). No significant relationship between breed and shunt type could be determined in cats. CONCLUSION: Breed has a significant influence on shunt anatomy in dogs. Animals presenting with signs of portosystemic shunting may suffer from a wide range of operable or inoperable conditions. Veterinarians should be aware that unusual or inoperable shunts are much more likely to occur in breeds that are not predisposed to congenital portosystemic shunts.     

Ultrasonographic findings in dogs with hyperammonemia: 90 cases (2000-2002)

OBJECTIVE: To determine ultrasonographic abnormalities in dogs with hyperammonemia. DESIGN: Retrospective study. ANIMALS: 90 client-owned dogs with hyperammonemia. PROCEDURE: Ultrasonography of the abdominal vessels and organs was performed in a systematic way. Dogs in which the ultrasonographic diagnosis was a congenital portosystemic shunt were included only if they underwent laparotomy or necropsy. Dogs in which the abdominal vasculature appeared normal and dogs in which the ultrasonographic diagnosis was acquired portosystemic shunts and portal hypertension were included only if liver biopsy specimens were submitted for histologic examination. RESULTS: Ultrasonography excluded portosystemic shunting in 11 dogs. Acquired portosystemic shunts were found in 17 dogs, of which 3 had arterioportal fistulae and 14 had other hepatic abnormalities. Congenital portosystemic shunts were found in 61 dogs, of which 19 had intrahepatic shunts and 42 had extrahepatic shunts. Intrahepatic shunts originated from the left portal branch in 14 dogs and the right portal branch in 5. Extrahepatic shunts originated from the splenic vein, the right gastric vein, or both and entered the caudal vena cava or the thorax. Ultrasonography revealed splenic-caval shunts in 24 dogs, right gastric-caval shunts in 9 dogs, splenic-azygos shunts in 8 dogs, and a right gastric-azygos shunt in 1 dog. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that ultrasonography is a reliable diagnostic method to noninvasively characterize the underlying disease in dogs with hyperammonemia. A dilated left testicular or ovarian vein was a reliable indicator of acquired portosystemic shunts.     

Post-prandial serum bile acid concentrations and ammonia tolerance in Maltese dogs with and without hepatic vascular anomalies

SUMMARY: Post-prandial serum bile acid concentrations were measured in 200 Maltese dogs in an attempt to identify those with subclinical portosystemic shunts. Five of these were later shown to have hepatic pathology or abnormal liver function. In the other 195 Maltese bile acid concentrations ranged from 1 to 362 μmol.L^-1 (mean ± SD, 70 ±50 μmol.L^-1; median, 65.0 μmol.L^-1). Of these, 79% were above the reference range (0 to 31 μmol.L^-1) established from 23 mixed-breed control dogs. It was therefore not possible to determine the prevalence of subclinical portosystemic shunts on the basis of bile acid determinations.
Further investigation of liver function was performed to investigate why bile acid concentrations were increased in these dogs. Rectal ammonia tolerance tests were normal in 102 of 106 Maltese tested and liver samples (11 dogs) and plasma biochemistry profiles (9 dogs) demonstrated no significant hepatic disease or dysfunction.
Of 2 Maltese with hyperammonaemia after administration of ammonium chloride, one had a large congenital portosystemic shunt that was confirmed at surgery. In the other there were no macroscopic portosystemic communications, but a liver biopsy showed histological changes consistent with microscopic portovascular dysplasia.
Total serum bile acid concentrations were consistently lower when assessed by highperformance liquid chromatography than by an enzymatic spectrophotometric method. This discrepancy was substantially larger in Maltese than in control dogs, suggesting the presence of an additional reacting substance in the serum of Maltese dogs.     

Use of transcolonic portal scintigraphy to evaluate efficacy of cellophane banding of congenital extrahepatic portosystemic shunts in 16 dogs

OBJECTIVE: To evaluate the efficacy of cellophane banding of single congenital extrahepatic portosystemic shunts in dogs using transcolonic portal scintigraphy. To investigate the portal circulation of those dogs with elevated postoperative shunt fractions to determine the cause of the persistent shunting. Further, to evaluate whether presenting signs, clinical pathology findings and liver histopathology are predictive of outcome. DESIGN: Prospective study of 16 dogs presenting with single congenital extrahepatic portosystemic shunts. PROCEDURE: Dogs with single extrahepatic portosystemic shunts attenuated by cellophane banding underwent portal scintigraphy and bile acids tolerance testing pre- and post-operatively. Dogs identified with elevated shunt fractions at 10 weeks post-operatively underwent mesenteric portovenography. Qualitative hepatic histopathology from all dogs was reviewed by a veterinary pathologist and assigned a semi-quantitative score to identify any abnormalities that may predict surgical outcome. RESULTS: At 10 weeks post cellophane banding, 10 of 16 cases (63%) had normal shunt fractions, whilst six dogs (37%) had increased shunt fractions and seven dogs (44%) had increased serum bile acids. Of these dogs, mesenteric portovenography revealed incomplete closure of the shunt in three dogs (18.6%) and multiple acquired shunts in three dogs (18.6%). Liver histopathology findings were similar for all dogs, regardless of outcome. CONCLUSIONS: Cellophane banding is an efficacious method for complete gradual occlusion of single extrahepatic shunts when the shunt vessel is attenuated to < or = 3 mm. Transcolonic portal scintigraphy is a reliable method for assessment of shunt attenuation and, unlike serum bile acids, is not influenced by other causes of liver dysfunction.     

Complete Ligation of Extrahepatic Congenital Portosystemi Shunts in Nonencephalopathic Dogs

Objective —To evaluate lack of encephalopathy as a positive prognostic factor for complete ligation of extrahepatic congenital portosystemic shunts in dogs.
Study Design —Retrospective analysis of case records.
Animals —Dogs with extrahepatic congenital portosystemic shunts treated at the Veterinary Medical Teaching Hospital of the College of Veterinary Medicine, Cornell University, from 1985 to 1996.
Methods —The ability to completely ligate the shunting vessel in 12 nonencephalopathic dogs was compared with that in 44 encephalopathic dogs with similar shunts.
Results —Clinical signs in the 12 nonencephalopathic dogs were related to ammonium biurate urolithiasis. All 12 dogs had single extrahepatic shunting vessels. The rate of complete ligation in the nonencephalopathic dogs was 92%, whereas the rate of complete ligation in the 44 encephalopathic dogs with single extrahepatic shunts was 59%. The ability to completely ligate the shunt in nonencephalopathic dogs was significantly better ( P = .04) than in the encephalopathic dogs.
Conclusion—Lack of encephalopathy is a positive prognostic factor for complete ligation of single extrahepatic congenital portosystemic shunts.
Clinical Relevance —In most affected dogs, extrahepatic congenital portosystemic shunts in nonencephalopathic dogs can be completely ligated.     

SIMULTANEOUS CONGENITAL AND ACQUIRED EXTRAHEPATIC PORTOSYSTEMIC SHUNTS IN TWO DOGS

Two dogs with simultaneous congenital and acquired portosystemic shunts are reported. The first dog was an eight-month-old, male Golden Retriever with a history of peritoneal effusion, polyuria/polydipsia, and stunted growth. The dog had a microcytic, hypochromic anemia, a mildly elevated AST, and a moderate to severely elevated preprandial and postprandial serum bile acids. Transcolonic portal scintigraphy confirmed the presence of a portosystemic shunt. An intraoperative mesenteric portogram was performed. Two conjoined congenital extrahepatic portosystemic shunts and multiple acquired extrahepatic portosystemic shunts were identified. The second dog was a five-month-old, mixed breed with two week history of peritoneal effusion. Abdominal ultrasound and transcolonic scintigraphy were used to diagnose a portosystemic shunt. A single extrahepatic portosystemic shunt, portal hypertension, and multiple acquired collateral shunts were identified at surgery. The histologic alterations observed in these dogs were consistent with a portosystemic shunt. In these dogs, the presence of congenital and acquired portosystemic shunts and histopathologic findings are considered to represent a combination of congenital portosystemic shunts and noncirrhotic portal hypertension or portal vein hypoplasia.     

ULTRASONOGRAPHIC DIAGNOSIS OF CONGENITAL PORTOSYSTEMIC SHUNTS IN DOGS: RESULTS OF A PROSPECTIVE STUDY

The aims of this study were to determine if accurate diagnosis of congenital portosystemic shunt was possible using two dimensional, grey-scale ultrasonography, duplex-Doppler, and color-flow Doppler ultrasonography in combination, and to determine if dogs with congenital portosystemic shunts have increased or variable mean portal blood flow velocity. Eighty-two dogs with clinical and/or clinicopathologic signs compatible with portosystemic shunting were examined prospectively. Diagnosis of congenital portosystemic shunt was subsequently confirmed in 38 of these dogs using operative mesenteric portography: 14(37%) dogs had an intrahepatic shunt and 24(63%) had an extrahepatic shunt. Ultrasonography had a sensitivity of 95%, specificity of 98%, and accuracy of 94%. Ultrasonographic signs in dogs with congenital portosystemic shunts included small liver, reduced visibility of intrahepatic portal vessels, and anomalous blood vessel draining into the caudal vena cava. Correct determination of intra - versus extrahepatic shunt was made ultrasonographically in 35/38 (92%) dogs. Increased and/or variable portal blood flow velocity was present in 21/30 (70%) dogs with congenital portosystemic shunts. In one dog with an intrahepatic shunt the ultrasonographic diagnosis was based partly on finding increased mean portal blood flow velocity because the shunting vessel was not visible. Detection of the shunting vessel and placement of duplex-Doppler sample volumes were facilitated by use of color-flow Doppler. Two-dimensional, grey-scale ultrasonography alone is sufficient to detect most intrahepatic and extrahepatic shunts; sensitivity is increased by additional use of duplex-Doppler and color-flow Doppler. Increased and/or variable portal blood flow velocity occurs in the majority of dogs with congenital portosystemic shunts.     

Canine congenital portosystemic encephalopathy

The case records of 21 dogs with congenital portosystemic encephalopathy are reviewed. The disorder was most common in Australian cattledogs (blue heelers; 8 cases), Old English sheepdogs (3 cases) and Maltese terriers (3 cases). Extra-hepatic shunts occurred in small breeds, with the exception of 1 cattledog, while intra-hepatic shunts occurred in the medium to large breeds. The most common clinical pathology abnormalities were abnormal ammonia tolerance, mild to moderate increases in plasma alanine aminotransferase or alkaline phosphatase concentrations, decreased total serum protein concentrations, increased fasting ammonia concentrations and ammonium biurate crystalluria. Radiological examination revealed that all the dogs had a small liver. The kidneys were enlarged in 5 of 10 dogs in which kidney size could be estimated. Surgical ligation of an extra-hepatic shunt was successful in 2 of 4 dogs in which it was attempted. Medical management resulted in alleviation of clinical signs in 5 of 8 dogs. The period of successful treatment ranged from a few months to over a year.     

Per Rectal Portal Scintigraphy Using 99mTechnetium Pertechnetate to Diagnose Portosystemic Shunts in Dogs and Cats

Per rectal portal scintigraphy using 99mTechnetium pertechnetate (99mTcO4-) was used to diagnose portosystemic shunts (PSS) before surgical confirmation in seven dogs and two cats. Shunt fractions, representing the percent of portal blood that bypasses the liver, were determined by computer analysis of the scintigraphic images. Animals with portosystemic shunts had a mean preoperative shunt fraction of 84.02% (n = 9). The mean postoperative shunt fraction in four animals was 58.22%. The mean shunt fraction in ten control dogs was 5.00%. Per rectal portal scintigraphy is an innovative, easily performed, inexpensive method to diagnose congenital portosystemic shunts in dogs and cats.     

Surgical Management of Multiple Congenital Intrahepatic Shunts in Two Dogs

Objective —To present details of an unusual type of portosystemic shunt and its surgical management in two dogs.
Animals —Two young dogs that had a tentative diagnosis of a portosystemic shunt on the basis of clinical signs and serum biochemical abnormalities. Abdominal ultrasonography and contrast portography demonstrated multiple intrahepatic shunts. In both cases, the multiple shunts arose from a single branch of the portal vein.
Outcome—It was possible to locate and attenuate flow through the shunts via a transportal venotomy under conditions of hepatic vascular occlusion. Clinical and biochemical abnormalities resolved after surgery in both dogs. Postoperative sonography revealed complete obliteration of the shunt plexus in one of the dogs.     

Coagulation profiles in dogs with congenital portosystemic shunts before and after surgical attenuation

BACKGROUND: Serious postoperative hemorrhage has been reported in dogs after closure of congenital portosystemic shunts (CPS). HYPOTHESIS: In dogs with portosystemic shunting, low coagulation factor activity is responsible for coagulopathy, which can cause complications after surgery. ANIMALS: Thirty-four dogs with CPS and 39 healthy dogs. METHODS: In a prospective study, coagulation times, platelet count, and the activity of 8 coagulation factors were measured in dogs before and after surgical shunt attenuation and in 31 healthy dogs. The effect of abdominal surgery on hemostasis was determined at ovariectomy in 8 healthy dogs. RESULTS: Dogs with CPS had lower platelet counts, lower activity of factors II, V, VII, and X, and increased factor VIII and activated partial thromboplastin time (APTT) compared to healthy dogs. After surgical attenuation, dogs with CPS had decreased platelet counts and activity of factors I, II, V, VII, IX, X, and XI and a prolonged prothrombin time (PT). Ovariectomy resulted in decreased activity of factors VII and X. Six weeks after surgery, portosystemic shunting persisted in 9 of 30 dogs, with no improvement of hemostatic values. CPS dogs without shunting had improved coagulation times and increased activity of factors II, V, VII, and X. CONCLUSIONS AND CLINICAL IMPORTANCE: Dogs with CPS have lower activity of clotting factors compared to healthy dogs, resulting in a prolonged APTT. Surgical attenuation of the shunt results in increased abnormalities in coagulation times and factors immediately after surgery. Hemostasis is normalized after complete recovery of shunting after attenuation, in contrast to dogs with persistent shunting.     

Congenital portosystemic shunts in toy and miniature poodles

Three male Poodles (two Toy, one Miniature) were presented to their veterinarians for evaluation of urolithiasis and varying degrees of hepatic encephalopathy. All three dogs were diagnosed as having intrahepatic shunts and referred for surgical correction. In each case, shunts arose from the right branch of the portal vein and were amenable to perivascular dissection caudal to where the vessel entered the hepatic parenchyma and to placement of perivascular cellophane bands to achieve shunt attenuation. During the same period, a female Miniature Poodle also presented for treatment of a congenital portosystemic shunt discovered during evaluation for generalised motor seizures. This animal had an extrahepatic portoazygous shunt that was completely ligated. Congenital portosystemic shunts have not previously been identified in Toy and Miniature Poodles at the University Veterinary Centre, Sydney and the anatomical types of shunt seen in this breed have not previously been reported in a consecutive series of cases. The three male dogs are noteworthy for a number of reasons: all had intrahepatic shunts, despite being small breed dogs; all three presented in a similar fashion, and all had shunts of an anatomical type amenable to placement of cellophane bands. One male dog died within 12 hours of surgery, the remaining three dogs survived and their liver function was normal at follow-up between 2 and 3 months after surgery. Use of cellophane bands for successful attenuation of intrahepatic shunts has not been previously reported.     

USE OF TRANSCOLONIC 123I-IODOAMPHETAMINE TO DIAGNOSE SPONTANEOUS PORTOSYSTEMIC SHUNTS IN 18 DOGS

Transcolonic ¹²³I-Iodoamphetamine is rapidly absorbed across the colonic mucosa and binds to amine receptors in the liver and lungs. During the first ten minutes following colonic administration, a simple ratio of lung counts to lung counts plus liver counts provides an accurate estimate of the fraction of portal blood that bypasses hepatic sinusoids in dogs with portosystemic shunts. Studies were performed on 24 dogs with suspect portosystemic shunt. Shunt fraction values for 18 dogs with surgically confirmed portosystemic shunt were obviously higher than published values for normal dogs, and also significantly higher than values for the other six dogs, later confirmed to lack shunts. Postoperative studies were repeated on ten dogs with single shunt vessels 1–2 days after shunt closure. Total shunt ligation resulted in normal postoperative shunt fraction, whereas partial shunt ligation resulted in persistant elevation of shunt fraction. Transcolonic iodoamphetamine scintigraphy is noninvasive, easy to perform, and provides an accurate method to diagnose dogs with portosystemic shunt.     

Neurological dysfunction in three dogs and one cat following attenuation of intrahepatic portosystemic shunts

Neurological dysfunction is an uncommon complication following extrahepatic portosystemic shunt ligation. Three dogs and one cat are described that developed neurological signs within 21 to 42 hours of attenuation of intrahepatic portosystemic shunts. None of these cases had biochemical evidence of hepatic encephalopathy postoperatively. Two dogs died during management of status epilepticus following aspiration of food. One dog died six months postoperatively. The cat had persistent neurological dysfunction at discharge, but was alive and had recovered most of its neurological function at the time of writing, 37 months after surgery. This report demonstrates the potential for animals with intrahepatic portosystemic shunts to develop postoperative neurological signs and highlights the difficulty of managing such cases. Two dogs had both intrahepatic and extrahepatic portosystemic shunts. Large intestinal malrotation (partial situs inversus) may have been linked to the development of a portosystemic shunt in the remaining dog.     

ANATOMY OF EXTRAHEPATIC PORTOSYSTEMIC SHUNTS IN DOGS AS DETERMINED BY COMPUTED TOMOGRAPHY ANGIOGRAPHY

Congenital extrahepatic portosystemic shunts are anomalous vessels joining portal and systemic venous circulation. These shunts are often diagnosed sonographically, but computed tomography (CT) angiography produces high‐resolution images that give a more comprehensive overview of the abnormal portal anatomy. CT angiography was performed on 25 dogs subsequently proven to have an extrahepatic portosystemic shunt. The anatomy of each shunt and portal tributary vessels was assessed. Three‐dimensional images of each shunt type were created to aid understanding of shunt morphology. Maximal diameter of the extrahepatic portosystemic shunt and portal vein cranial and caudal to shunt origin was measured. Six general shunt types were identified: splenocaval, splenoazygos, splenophrenic, right gastric‐caval, right gastric‐caval with a caudal shunt loop, and right gastric‐azygos with a caudal shunt loop. Slight variations of tributary vessels were seen within some shunt classes, but were likely clinically insignificant. Two shunt types had large anastomosing loops whose identification would be important if surgical correction were attempted. A portal vein could not be identified cranial to the shunt origin in two dogs. In conclusion, CT angiography provides an excellent overview of extrahepatic portosystemic shunt anatomy, including small tributary vessels and loops. With minor variations, most canine extrahepatic portosystemic shunts will likely be one of six general morphologies.     

Hemostatic profiles in 39 dogs with congenital portosystemic shunts

OBJECTIVES: To determine if there were significant changes in prothrombin time (PT), partial thromboplastin time (PTT), and fibrinogen levels in dogs with naturally occurring congenital portosystemic shunts (CPSS) and to determine if there was any association between these values, serum albumin concentration, and the ability to attenuate the shunt vessel. STUDY DESIGN: Retrospective clinical study. ANIMALS: Thirty-nine client-owned dogs. METHODS: Medical records of 60 dogs with confirmed CPSS were retrospectively evaluated. Hemostatic profiles had been performed before surgery in 39 cases. RESULTS: Dogs with CPSS had significantly higher values for PTT (P < .001) when compared with normal dogs. Of the total number of dogs, 64.1% had a PTT greater than 16 seconds (25/39). PTT was prolonged by 25% or more in 51.3% of dogs (20/39). PT tended to be higher in dogs with CPSS (P = .036), although only 7.7% (3/39) of dogs had a PT greater than 12 seconds (the maximum reference value). Dogs with CPSS had significantly lower values for albumin and fibrinogen (P < .001). Platelet numbers were within the normal range in 87.2% of cases (34/39). Of the 5 dogs with platelet numbers outside the normal range, 3 were mildly thrombocytopenic. Fibrin degradation product concentrations were not elevated in any dogs tested (N = 22). There was no significant difference in any of the measured variables between dogs with extrahepatic shunts and those with intrahepatic shunts (P > .1). For PT, PTT, albumin, and fibrinogen, there was no significant difference between dogs that underwent total, partial, or no attenuation (P > .3). CONCLUSIONS: Dogs with CPSS have a tendency to have a prolonged PTT. There was no significant difference in hemostatic profile results between dogs with intrahepatic shunts versus extrahepatic shunts. Preoperative hemostatic profile abnormalities were not useful as predictors of ability to attenuate CPSS. CLINICAL RELEVANCE: Prolonged PTT was not associated with bleeding tendencies in any of the dogs. Assays of individual clotting factors may help to further characterize the abnormalities present in animals with CPSS and may identify specific factor deficiencies. This might enable identification of a noninvasive diagnostic or prognostic indicator.     

Outcomes of cellophane banding for congenital portosystemic shunts in 106 dogs and 5 cats

OBJECTIVE : To report outcomes after cellophane banding of single congenital portosystemic shunts in dogs and cats. STUDY DESIGN : Retrospective study of sequential cases. ANIMALS : One hundred and six dogs and five cats. METHODS : Medical records were reviewed for breed, sex, age at surgery, shunt anatomy, results of pre- and postoperative biochemical analysis, development of postligation neurologic dysfunction, portal hypertension or other serious complications, and the owners' perception of their animal's response to surgery. RESULTS : Ninety-five dogs and all 5 cats had extrahepatic shunts. Eleven dogs had intrahepatic shunts. Six dogs (5.5%) died as a result of surgery from portal hypertension (2 dogs), postligation neurologic dysfunction (2), splenic hemorrhage (1) and suspected narcotic overdose (1). Serious complications were more common in dogs with intrahepatic shunts than those with extrahepatic shunts (P=.002). Postligation neurologic dysfunction necessitated treatment in 10 dogs and 1 cat; 8 dogs and the cat survived. Clinical signs attributed to portosystemic shunting resolved or were substantially attenuated in all survivors. Postoperative serum bile acid concentrations or results of ammonia tolerance testing were available for 88 animals; 74 (84%) were normal and 14 (16%) were abnormal. Multiple acquired shunts were documented in two animals. CONCLUSIONS : Cellophane banding is a safe and effective alternative to other methods of attenuation. CLINICAL RELEVANCE : Slow occlusion of portosystemic shunts using a variety of methods is being evaluated world wide. Cellophane banding is a relatively simple procedure with comparable safety and efficacy to previously reported techniques.     

Serum gastrin concentrations in dogs with liver disorders

Dogs with liver disorders often display gastrointestinal signs that may be triggered by ulceration. The liver is important for inactivation of some forms of gastrin. Therefore, hypergastrinaemia has been implicated in the pathogenesis of gastrointestinal ulcerations related to liver dysfunction. The aim of this study was to determine serum gastrin concentrations in dogs with liver disease. Fasted blood samples were collected from 15 dogs with newly diagnosed liver disease and 18 healthy dogs. Gastrin concentrations were significantly lower in dogs with congenital portosystemic shunt compared with healthy dogs (P=0.003). No significant difference (P=0.6) in gastrin concentration was revealed between dogs with hepatocellular disease and healthy dogs. Serum gastrin concentrations were not significantly associated with the occurrence of vomiting, anorexia, diarrhoea, or melaena in dogs with liver disorders. These findings did not provide support for the role of hypergastrinaemia in the development of gastrointestinal signs associated with liver disease in dogs. Decreased serum concentrations of gastrin in a dog with liver disease may suggest the presence of portosystemic shunt. Further investigation is warranted to determine the importance of hyopogastrinaemia in congenital postosystemic shunts in dogs and to evaluate potential alterations in serum gastrin concentrations in specific hepatocellular diseases.     

USE OF QUANTITATIVE HEPATIC SCINTIGRAPHY TO EVALUATE SPONTANEOUS PORTOSYSTEMIC SHUNTS IN 12 DOGS

Quantitative hepatic scintigraphy is a valid means for estimating total liver blood flow and relative portal hepatic perfusion. The Hepatic perfusion index (HPI) was determined for a group of 12 dogs with portosystemic shunts prior to and two days after corrective surgery. HPI values for the dogs prior to operation were significantly elevated (p<0.001) as compared with those for a group of normal dogs, indicating reduced effective portal hepatic perfusion in dogs with shunts. Dogs showing a favorable clinical response after surgery had a significant decrease (p<0.02) in HPI values after operation. One dog showing a poor clinical response after operation had an increase in HPI score after operation. Quantitative hepatic scintigraphy is a valuable diagnostic test for screening presumptive cases of portosystemic shunts and monitoring the response to surgical intervention.     

USE OF MAGNETIC RESONANCE ANGIOGRAPHY FOR DIAGNOSIS OF PORTOSYSTEMIC SHUNTS IN DOGS

A prospective study was conducted to determine the sensitivity and specificity of diagnosis of portosystemic shunts (PSS) and the accuracy of anatomically locating single congenital PSS in dogs using magnetic resonance angiography (MRA). MRA was performed on 10 normal dogs and 23 dogs with PSS. Sensitivity and specificity of MRA to diagnose any shunt among all dogs were 80% and 100%, respectively. Among dogs identified with PSS, sensitivity and specificity of MRA for diagnosis of multiple extrahepatic shunts were 63% and 97%, respectively, and for diagnosis of single congenital shunts were 79% and 100%, respectively. Using MRA, radiologists correctly identified shunts as extrahepatic or intrahepatic in 83% of patients and correctly identified the origin and insertion of the shunts in 57% and 97% of patients, respectively. Use of MRA is specific for diagnosis of PSS and is a sensitive indicator of anatomic location of single congenital portosystemic shunts.