Evaluation of ameroid ring constrictors for the management of single extrahepatic portosystemic shunts in cats: 23 cases (1996-2001)

OBJECTIVE: To document the signalment; history; clinical signs; clinicopathologic, diagnostic imaging, and surgical findings; perioperative complications; and long-term clinical results of ameroid ring constrictor (ARC) placement on single extrahepatic portosystemic shunts (PSS) in cats. DESIGN: Retrospective study. ANIMALS: 23 cats treated with an ARC on a single extrahepatic PSS. PROCEDURE: An ARC was placed surgically around the PSS. Portal pressure was measured prior to ARC placement, with complete temporary PSS occlusion, and after ARC placement. Cats were scheduled for recheck transcolonic portal scintigraphy 8 to 10 weeks after surgery. Follow-up information was obtained by telephone interview with the owners. RESULTS: An ARC was successfully placed in 22 of 23 cats. Intraoperative complications, consisting of PSS hemorrhage, occurred in 2 cats. Mean (+/- SD) portal pressure (n = 15) was 6.7+/-2.9 mm Hg before PSS manipulation, 18.6+/-7.7 mm Hg with complete temporary PSS occlusion, and 6.9+/-2.7 mm Hg after ARC placement. Postoperative complications developed in 77% (17 of 22) of cats after ARC placement, and included central blindness, hyperthermia, frantic behavior, and generalized motor seizures. Perioperative mortality rate was 4.3% (1 of 23). Persistent shunting was identified in 8 of 14 cats. Overall, 75% (15 of 20) of cats had an excellent long-term outcome. CONCLUSIONS AND CLINICAL RELEVANCE: Placement of an ARC on single extrahepatic PSS in cats resulted in low surgical complication and perioperative mortality rates, but most cats did have substantial postoperative complications. Persistent shunting was common, although many cats with persistent shunting were clinically normal.     

Evaluation of ameroid ring constrictors for treatment for single extrahepatic portosystemic shunts in dogs: 168 cases (1995-2001)

OBJECTIVES: To evaluate use of an ameroid ring constrictor (ARC) for treatment for single extrahepatic portosystemic shunts (PSSs) and identify factors associated with postoperative death, continued portosystemic shunting, and long-term outcome in dogs. DESIGN: Retrospective study. ANIMALS: 168 dogs with a single extrahepatic PSS. PROCEDURE: Medical records of dogs that had a single extrahepatic PSS and were treated with an ARC were reviewed. Signalment, history, clinical signs, results of preoperative blood analyses and portal pressure measurements, PSS location, ARC size, postoperative complications, and postoperative scintigraphy results were recorded. Owners were interviewed 6 months to 6 years after surgery. Results-Postoperative complications developed in 10% of dogs. Postoperative mortality rate was 7.1%. Predictive factors for postoperative death included high preoperative WBC count and postoperative complications. Twenty-one percent of dogs in which portal scintigraphy was performed 6 to 10 weeks after surgery had continued shunting. Predictive factors for persistent shunting included low preoperative plasma albumin concentration, high portal pressure after complete occlusion, and high portal pressure difference (postocclusion minus baseline). Clinical outcome in 108 dogs was classified as excellent (80%), good (14%), or poor (6%). Predictive factors for excellent long-term clinical outcome included high preoperative plasma albumin concentration, low preoperative leukocytosis, low portal pressure after complete occlusion, absence of postoperative seizures, and absence of continued shunting. CONCLUSIONS AND CLINICAL RELEVANCE: Use of an ARC for treatment for a single extrahepatic PSS resulted in low morbidity and mortality rates. Certain preoperative factors were associated with increased risk of postoperative death, continued portosystemic shunting, and long-term outcome.     

Association of portovenographic findings with outcome in dogs receiving surgical treatment for single congenital portosystemic shunts: 45 cases (2000-2004)

OBJECTIVE: To determine whether hepatic portal vascularity, as assessed by intraoperative mesenteric portovenography (IMP), is related to outcome in dogs undergoing attenuation of single congenital portosystemic shunts (CPSSs). DESIGN: Retrospective case series. ANIMALS: 45 dogs, each with a single CPSS, in which IMP was performed before and after temporary complete occlusion of the shunting vessel and that underwent complete (17 dogs) or partial (28 dogs) CPSS attenuation (surgery 1). PROCEDURES: Medical records were reviewed for signalment, clinical history, and bile acids stimulation test results. Intrahepatic portal vessel (IPV) opacification in pre- and postocclusion portovenograms was graded to determine whether the degree of opacification was correlated with the degree of shunt attenuation, clinical or biochemical factors, or long-term clinical outcome. In 17 of 28 dogs that had partial CPSS attenuation, these procedures were subsequently repeated (surgery 2) to achieve complete (14 dogs) or further partial (3 dogs) CPSS attenuation. RESULTS: Compared with preattenuation findings, IPV opacification increased significantly after partial or complete CPSS attenuation. The degree of IPV opacification before and after CPSS occlusion (surgery 1) was greater in dogs that tolerated complete versus partial CPSS attenuation and was correlated positively with age. The degree of IPV opacification following CPSS occlusion (surgery 1) was maximal in all dogs without encephalopathy and was correlated negatively with follow-up preprandial serum bile acids concentrations and positively with clinical improvement. CONCLUSIONS AND CLINICAL RELEVANCE: Data suggest that IMP can be used to assess changes in IPV blood flow and help predict outcome following attenuation of single CPSSs in dogs.     

A comparison of the Ameroid constrictor versus ligation in the surgical management of single extrahepatic portosystemic shunts.

Twenty-two dogs were managed surgically for a single extrahepatic portosystemic shunt; 12 with surgical ligation and 10 with an Ameroid constrictor. Utilization of the Ameroid constrictor significantly decreased surgery time to approximately half that of the ligation technique. A decreased intraoperative and postoperative complication rate was noted with the Ameroid constrictor group. Follow-up evaluation demonstrated comparable efficacy when comparing surgical techniques. The Ameroid constrictor offered a surgical occlusion technique for management of a single extra-hepatic portosystemic shunt that was equally effective to ligation while shortening surgical time and minimizing the risks that are commonly associated with ligation of the shunting vessel.     

Perioperative outcomes after three different single extrahepatic portosystemic shunt attenuation techniques in dogs: partial ligation, complete ligation and ameroid constrictor placement

OBJECTIVE: To compare the perioperative outcomes of single extrahepatic portosystemic shunt occlusion by complete and partial silk ligation and ameroid constrictor placement in dogs. DESIGN: A retrospective analysis of 30 dogs with single congenital extrahepatic shunts. PROCEDURE: Records between 1990 and 2000 were reviewed. Patient age, breed, weight, presenting clinical signs, clinical pathology results, diagnostic imaging results, the surgery procedure performed, implant used, time taken, intra operative complications and perioperative complications were recorded. Mortality rates were calculated. RESULTS: Twenty dogs had a silk ligation procedure, 10 partially occluded and 10 completely. Ten dogs had an ameroid constrictor placement procedure. Ameroid constrictor surgery was significantly shorter in duration than silk ligation. Time for silk ligation was 91.8 +/- 35.2 minutes (median 90.0); time for ameroid constrictor placement was 71.5 +/- 12.0 (median 72.5, P = 0.049). A reduction in intraoperative complications was also noted in the ameroid constrictor surgery group. CONCLUSION: The ameroid constrictor offered a surgical occlusion procedure of single extrahepatic portosystemic shunts in dogs that was clinically as effective as silk ligation in the perioperative period, with a significantly shorter surgery time.     

Neurological dysfunction in dogs following attenuation of congenital extrahepatic portosystemic shunts

Eleven of 89 dogs (12 per cent) developed neurological signs within six days of surgical attenuation of a congenital extrahepatic portosystemic shunt. Neurological signs were not associated with hepatic encephalopathy or hypoglycaemia. Signs varied in severity from non-progressive ataxia (three dogs) to generalised motor seizures (four dogs), progressing to status epilepticus (three dogs). In a further four cases, ataxia and disorientation were treated vigorously with anticonvulsant medication, presumably preventing the development of seizures. Two dogs that developed status epilepticus died or were eventually euthanased. All other animals survived, although some had persistent neurological deficits. Postligation neurological complications were not prevented by gradual shunt attenuation. Prophylactic treatment with phenobarbitone (5 to 10 mg/kg preoperatively, followed by 3 to 5 mg/kg every 12 hours for three weeks) did not significantly reduce the incidence of neurological sequelae (2/31 [6 per cent] dogs with phenobarbitone vs 9/58 [16 per cent] without phenobarbitone; P = 0.2). However, no animal receiving phenobarbitone experienced generalised motor seizures or status epilepticus. In conclusion, these observations suggest that postligation neurological syndrome comprises a spectrum of neurological signs of variable severity. Perioperative treatment with phenobarbitone may not reduce the risk of neurological sequelae, but may reduce their severity.     

Ultrasonographic evaluation of partially attenuated congenital extrahepatic portosystemic shunts in 14 dogs

Doppler ultrasonography was used to evaluate the portal vein in 14 dogs before, immediately after and four weeks after a partial ligation of a congenital extrahepatic portocaval shunt. By four weeks after the operation, the hepatofugal or zero flow in the portal vein segment cranial to the shunt origin had become a hepatopetal flow in 13 of the dogs, which became clinically healthy. The other dog continued to have a hepatofugal flow in the portal vein cranial to the origin of the shunt and continued to show clinical signs of hepatic encephalopathy. The shunt remained functional in six of the dogs, and three of them developed portosystemic collaterals in addition. In the other eight dogs the patent shunt was non-functional, because a hepatopetal flow was detected in the shunt adjacent to the portal vein. This flow was the result of the splenic vein entering the shunt, and the splenic blood dividing; some flowed via the shunt towards the portal vein, preventing the portal blood from shunting, and the rest flowed via the attenuated shunt segment to the caudal vena cava. Shunting of the splenic venous blood was clinically insignificant.     

Congenital portosystemic shunts in dogs: 46 cases (1979-1986)

Congenital portosystemic shunts (CPSS) were diagnosed in 46 dogs. The historic, physical, and laboratory findings were tabulated. Half of the affected males were cryptorchid. Urolithiasis was detected in 20% of the dogs. The biochemical tests with the best sensitivity for the diagnosis of CPSS were sulfobromophthalein retention, fasting serum ammonia concentration, and serum alkaline phosphatase activity. The survival time and quality of life were assessed by physical and biochemical reevaluation of the dogs and by means of a questionnaire that was completed by the owners. Five dogs were treated medically. Thirty-three dogs were treated surgically. Dogs that had complete surgical occlusion of the CPSS became normal, and quality of life was excellent. Dogs that had partial occlusion of the CPSS improved, and some became clinically normal. Dogs that did not have surgical correction of the CPSS had continuation of signs, but several survived for years.     

Survival and prognostic indicators for dogs with intrahepatic portosystemic shunts: 32 cases (1990-2000)

OBJECTIVE: To determine prognostic indicators for short-term outcome and long-term survival for dogs with intrahepatic portosystemic shunts (IPSS). STUDY DESIGN: Retrospective study. ANIMALS: Thirty-two dogs of various breeds. METHODS: Clinical data extracted from medical records of dogs with IPSS were reviewed and included gender, age at surgery, weight, preoperative packed cell volume (PCV), total plasma protein concentration (TP), albumin (ALB), serum activities of alanine aminotransferase (ALT) and alkaline phosphatase (ALP), preprandial and postprandial bile acid concentrations (pre-BA, post-BA), blood urea nitrogen (BUN), glucose concentration, band neutrophils, per-rectal nuclear scintigraphy shunt fraction, whether an angiogram was performed, shunt location at surgery, whether a partial or complete attenuation of the shunt was performed, rectal temperature at the end of surgery, and duration of surgical procedure. Follow-up was determined from visits to the veterinary teaching hospital or by telephone communications with the owner or referring veterinarian. RESULTS: Median survival time was 35.68 months, and 1- and 2-year probabilities of survival were 60% and 55%, respectively. Body weight, TP, ALB, and BUN were identified as prognostic indicators for short-term outcome. PCV and TP were identified as prognostic indicators for long-term survival. CONCLUSIONS: PCV and TP were identified as prognostic indicators for long-term survival, whereas body weight, TP, ALB, and BUN were identified as indicators for short-term outcome in dogs with IPSS. Shunt location at surgery did not have any effect on short-term outcome and long-term survival. CLINICAL RELEVANCE: Total protein, ALB, BUN, and PCV can be used to determine prognosis of dogs with intrahepatic shunt.     

Portosystemic shunts in cats: seven cases (1976-1984)

Congenital portosystemic venous shunt causing signs of hepatic encephalopathy was diagnosed in 7 cats. The left gastric vein served as the shunt in four of these. Increases in blood ammonia and postprandial serum bile acids were the most consistent serum biochemical abnormalities. Excessive variation in red blood cell shape was a common but nonspecific hematologic finding. The jejunal-mesenteric venous injection of contrast material was the preferred method of portography to diagnose portosystemic shunts. Two cats were treated successfully by partial surgical occlusion of their shunts.     

Association of breed with the diagnosis of congenital portosystemic shunts in dogs: 2,400 cases (1980-2002)

OBJECTIVE: To determine the annual and overall proportion of diagnoses of congenital portosystemic shunts (CPSS) in dogs and identify breeds at increased risk for CPSS. DESIGN: Retrospective study. ANIMALS: 2,400 dogs with CPSS from veterinary teaching hospitals that reported to the Veterinary Medical Database (VMDB) from January 1, 1980 to February 28, 2002. PROCEDURE: The proportion of diagnoses of CPSS was calculated for all dogs and each breed recorded in the VMDB annually and for the 22.2-year period. Odds ratios and adjusted confidence intervals were calculated for breeds with at least 100 accessions by comparing odds of each breed with a diagnosis of CPSS with that of mixed-breed dogs. RESULTS: Congenital portosystemic shunts were reported in 0.18% of all dogs and 0.05% of mixed-breed dogs. The proportion of diagnoses of CPSS increased from 5 in 10,000 dogs in 1980 to 5 in 1,000 dogs in 2001. Yorkshire Terriers had the greatest total number of diagnoses of CPSS. Thirty-three breeds were significantly more likely to have a diagnosis of CPSS, compared with mixed-breed dogs. The greatest proportions of diagnoses were found in Havanese (3.2%), Yorkshire Terriers (2.9%), Maltese (1.6%), Dandie Dinmont Terriers (1.6%), and Pugs (1.3%). CONCLUSIONS AND CLINICAL RELEVANCE: Certain breeds appear to be at increased risk for CPSS, compared with mixed-breed dogs. The increased odds ratios among specific breeds support the hypothesis of a genetic predisposition for CPSS. Clients and veterinarians should consider appropriate diagnostic tests for dogs with clinical signs and those used for breeding from breeds with increased risk of CPSS.     

Gauged attenuation of congenital portosystemic shunts: results in 160 dogs and 15 cats

Portosystemic shunts were ligated over a gauged stainless steel rod in 160 dogs and 15 cats, using a midline celiotomy. The diameter of the rod varied with the size of the shunt and the diameter of the portal vein cranial to the shunt. Shunts were narrowed to the smallest diameter that did not cause signs of portal hypertension such as cyanosis of the stomach, pancreas, and small intestine. A slight discoloration was accepted only if the heart rate, end-expiratory CO2%, or arterial blood pressure (if available) did not deviate more than 15% from the values that were recorded at the beginning of the surgical procedure. The perioperative mortality (0-30 days) was 29%. The most common cause of death was euthanasia because of hypoplasia of the portal vein cranial to the shunt. Animals with intrahepatic shunts had a significantly lower probability of survival than animals with extrahepatic portocaval or portoazygos shunts. In dogs, large breed and a high body weight were also significant risk factors for non-survival. Age had a significant effect on risk of non-survival, with an increased risk for older dogs, irrespective of the breed of the dog (large breed vs. small breed). The probability of survival without recurrence of hepatoencephalopathy (HE) after 1 and 4 years was 61.3% and 55.7%, respectively. The only variable that was significantly associated with non-recurrence of HE was the breed of the dog, there being a lower probability for large breeds. Among the animals that survived surgery for more than 30 days, there was a significant higher probability of recurrence of HE in cats than in dogs.