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.     

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.     

Postattenuation neurologic signs after surgical attenuation of congenital portosystemic shunts in dogs: A review

The development of postattenuation neurologic signs (PANS) is a poorly understood and potentially devastating complication after surgical attenuation of congenital portosystemic shunts in dogs. Postattenuation neurologic signs include seizures but also more subtle neurologic signs such as depression, behavioral changes, tremors, and twitching. They most commonly occur within 7 days postoperatively and are typically unrelated to hyperammonemia, hypoglycemia, or electrolyte disturbances. This narrative review summarizes the findings of 50 publications from 1988-2020 that report occurrence of PANS. While most published reports included only dogs affected by postattenuation seizures (PAS), others included dogs with any form of PANS. Overall, PANS (including PAS) affected 1.6%-27.3% of dogs, whereas incidence of PAS ranged from 0%-18.2%. The etiology of PANS remains unknown; however, several theories have been proposed. Risk factors include preoperative hepatic encephalopathy, increasing age, and possibly certain breeds and extrahepatic shunt morphology. There is increasing evidence that prophylactic antiepileptic drugs do not prevent PANS. Treatment is centered around controlling neurologic signs with antiepileptic drugs and providing supportive intensive care. The 30-day survival rate in studies that included a minimum of four dogs affected by PANS was 0%-100% (median, 50.0%) and 0%-75.0% (median, 37.5%) for those with PAS. Mortality associated with PANS was typically related to occurrence of generalized seizure activity. Prognostic factors positively associated with short-term survival included having a history of preoperative seizures and development of focal seizures only. If affected dogs survived to discharge, survival for several years was possible, and the majority of neurologic signs manifested as part of the phenomenon of PANS appeared to resolve.     

Ultrasonographic assessment of hemodynamic changes in the portal vein during surgical attenuation of congenital extrahepatic portosystemic shunts in dogs

OBJECTIVE: To determine portal hemodynamic changes associated with surgical shunt ligation and establish ultrasonographic criteria for determining the optimal degree of shunt narrowing and predicting outcome. DESIGN: Case series. ANIMALS: 17 dogs, each with a single congenital extrahepatic portosystemic shunt. PROCEDURE: Pre- and postligation flow velocities and flow directions were determined by Doppler ultrasonography intraoperatively in the shunt and in the portal vein cranial and caudal to the shunt origin. Outcome was evaluated 1 month after surgery by measuring blood ammonia concentration and performing abdominal ultrasonography. RESULTS: Hepatofugal flow was detected in 9 of 17 dogs before shunt attenuation in the portal segment that was between the shunt origin and the entering point of the gastroduodenal vein. If hepatofugal flow became hepatopetal after shunt ligation, hyperammonemia resolved. Hepatofugal portal flow was caused by blood that flowed from the gastroduodenal vein toward the shunt. Shunt attenuation converted hepatofugal flow to hepatopetal in the shunt in 12 of 17 dogs. Chronic portal hypertension developed or perioperative death occurred when the portal congestion index caudal to the shunt origin increased by > 3.6 times. CONCLUSIONS AND CLINICAL RELEVANCE: After hepatopetal flow in the cranial portal vein and the shunt is established, further shunt narrowing is contraindicated. Increase of the portal congestion index caudal to the shunt > 3.5 times should be avoided. Poor outcome because of severe hypoplasia of the portal branches can be expected if the flow direction remains hepatofugal after shunt occlusion cranial to the shunt origin.     

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.     

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.     

Evaluation of cellophane banding with and without intraoperative attenuation for treatment of congenital extrahepatic portosystemic shunts in dogs

OBJECTIVE: To evaluate the effect of intraoperative attenuation of congenital extrahepatic portosystemic shunts (CEPSSs) during cellophane banding procedures in dogs. STUDY DESIGN: Retrospective case series and prospective study. ANIMALS: 18 cases evaluated retrospectively and 14 dogs evaluated prospectively. PROCEDURES: Gradual occlusion of CEPSSs was performed via cellophane banding. Shunts were occluded to a diameter < 3.0 mm during surgery in dogs prospectively enrolled in the partial attenuation group, whereas the shunt was not attenuated during surgery in dogs prospectively enrolled in the no-attenuation group or in dogs that had previously undergone surgery and were retrospectively evaluated. Postprandial serum bile acids (PPSBA) concentrations were measured before surgery and at various time points after surgery. RESULTS: Mean +/- SD PPSBA concentrations were 26.8 +/- 24.5 micromol/L at < 2.25 months after surgery (n = 16 dogs), 22.1 +/- 14.0 micromol/L from 2.25 to 6 months after surgery (12 dogs), and 34.9 +/- 32.5 micromol/L at > 6 months after surgery (22 dogs). In the prospectively enrolled dogs, mean PPSBA concentrations increased over time in dogs in the partial attenuation group, but not in dogs in the no-attenuation group. CONCLUSIONS AND CLINICAL RELEVANCE: Cellophane banding may be used to occlude larger CEPSSs and may decrease the need for intraoperative monitoring of portal vein blood pressure. The technique may facilitate minimally invasive treatment of CEPSSs in dogs. Intraoperative attenuation of CEPSSs to a diameter < 3.0 mm is not necessary and may result in a less favorable outcome.     

Medical management of congenital portosystemic shunts in 27 dogs—a retrospective study

Case records of 27 dogs with medically managed congenital portosystemic shunts were reviewed. Fourteen were followed up by telephone questionnaires to the owners. Age, breed, sex, clinical signs and blood results were similar to previous studies. Weight and quality of life were stable or improved on treatment in all cases. Total serum protein concentration and alanine aminotransferase and alkaline phosphatase activities fell significantly during treatment. Fourteen dogs were euthanased, four were lost to follow-up and nine remained alive. Mean survival time for the dogs euthanased was 9.9 months. Mean follow-up period for the dogs still alive was 56.9 months and all had survived more than 36 months from diagnosis. Surviving dogs with intrahepatic shunts had a significantly shorter follow-up period than dogs with extrahepatic shunts. Two prognostic indicators were identified, age at initial signs and blood urea concentration on presentation, both correlating with survival time. It was demonstrated that a significant proportion of dogs with portosystemic shunts managed medically have a good prognosis.     

Ultrasonography in the diagnosis of congenital portosystemic shunts in dogs

Summary

The value of ultrasonographic examination in the diagnosis of congenital portosytemic shunts was assessed in 36 dogs, using the right lateral approach. The sensitivity, specificity, and accuracy were 0.74, 1.0, and 0.86 respectively. The conclusion is that ultrasonography is highly specific and reasonably sensitive in diagnosing congenital portosystemic shunts in dogs     

Progressive remission of portosystemic shunting in 23 dogs after partial closure of congenital portosystemic shunts

The congenital portosystemic shunts in 23 dogs were closed partially in 18 and completely in five with a single silk ligature. The clinical results were studied and the degree of portosystemic shunting was measured by a scintigraphic method, the results being expressed as the shunt index (SI). In 17 of the dogs, the mean (sd) SI decreased from 0.92 (0.16) before surgery to 0.34 (0.25) during surgery after the attenuation of the shunt, and then to 0.10 (0.12) one month later. The dogs' venous ammonia concentration decreased from 203 (122) microM before surgery to 36 (18) one month after surgery. At the same time the clinical scores improved significantly. There were positive correlations between the SI and the general evaluation of the dogs' well-being by their owners (rs = 0.60), the ammonia concentration (rs = 0.86), and the diameter of the shunt (rs = 0.86). In the other six dogs, the intraoperative and/or postoperative SI was high. In two of them the shunt was further attenuated during a second operation, which resulted in lower SI values; in two a second small shunt was responsible for the high SI; in one multiple portosystemic shunts were found postmortem; and one dog was lost to follow-up.     

Determination of inheritance of single congenital portosystemic shunts in Yorkshire terriers

A hereditary basis for congenital portosystemic shunts (PSS) in Yorkshire terriers was explored through record and pedigree analysis and a breeding trial. The odds ratio for PSS in Yorkshire terriers was 35.9 times greater than for all other breeds combined. Wright's coefficient of inbreeding was approximately twice as high for Yorkshire terriers with PSS as compared to normal members of the breed (P=0.09). No common ancestors were found that were significant to the PSS group. Two affected Yorkshire terriers were bred and produced two normal puppies. Congenital PSS appears to be hereditary in Yorkshire terriers; however, the mechanism of inheritance has yet to be elucidated.     

The pathophysiology and laboratory diagnosis of congenital portosystemic shunts in dogs

Abstract Congenital portosystemic shunts generally arise as single vascular anomalies that cause the portal blood to bypass the liver and enter the systemic venous circulation directly. The liver is primarily affected, as it is deprived of perfusion by portal hepatotrophic factors such as insulin, glucagon, and amino acids. There is progressive hepatic atrophy, and as a consequence, dysfunction. Hepatic encephalopathy can result from increased levels of ammonia and gamma-aminobutyric acid within the systemic circulation. Variably toxic amines, captans and short chain fatty acids may act as false neurotransmitters. Hypoglycaemia will exacerbate the effects of these substances. Increased concentrations of ammonia and uric acid in the urine predispose to the precipitation of ammonium biurate crystals and the formation of calculi. Haematological changes include anaemia, microcytosis, hypoproteinaemia, leucocytosis, and coagulation abnormalities. Gastrointestinal effects are common. They may be displayed as anorexia, vomiting, ptyalism, pica, diarrhoea, or polyphagia. Most dogs are less than 1 year of age at initial presentation. Diagnosis from a laboratory viewpoint will involve a consideration of the history, clinical findings, haematology, serum biochemistry and urinalysis. If the findings are suggestive of a congenital portosystemic shunt, the demonstration of elevated fasting or, more consistently, post-prandial serum bile acid concentrations, and subsequent histological examination of a liver biopsy will provide a definitive diagnosis.     

Cellophane banding of congenital intrahepatic portosystemic shunts in two Irish wolfhounds

Two three-month-old, male Irish wolfhound siblings were diagnosed with breed-typical left divisional congenital intrahepatic portosystemic shunts consistent with patent ductus venosus. The shunts were amenable to surgical dissection at a posthepatic location. Both dogs had cellophane banding for shunt attenuation. One dog was euthanased after developing post-ligation neurological dysfunction, which was refractory to treatment. The other dog survived and demonstrated shunt attenuation. Successful surgical management using cellophane banding of a patent ductus venosus has not been previously described in a large-breed dog.     

The pathophysiology and laboratory diagnosis of congenital portosystemic shunts in dogs

Congenital portosystemic shunts generally arise as single vascular anomalies that cause the portal blood to bypass the liver and enter the systemic venous circulation directly. The liver is primarily affected, as it is deprived of perfusion by portal hepatotrophic factors such as insulin, glucagon, and amino acids. There is progressive hepatic atrophy, and as a consequence, dysfunction.

Hepatic encephalopathy can result from increased levels of ammonia and gamma-aminobutyric acid within the systemic circulation. Variably toxic amines, captans and short chain fatty acids may act as false neurotransmitters. Hypoglycaemia will exacerbate the effects of these substances. Increased concentrations of ammonia and uric acid in the urine predispose to the precipitation of ammonium biurate crystals and the formation of calculi.

Haematological changes include anaemia, microcytosis, hypoproteinaemia, leucocytosis, and coagulation abnormalities. Gastrointestinal effects are common. They may be displayed as anorexia, vomiting, ptyalism, pica, diarrhoea, or polyphagia. Most dogs are less than 1 year of age at initial presentation.

Diagnosis from a laboratory viewpoint will involve a consideration of the history, clinical findings, haematology, serum biochemistry and urinalysis. If the findings are suggestive of a congenital portosystemic shunt, the demonstration of elevated fasting or, more consistently, post-prandial serum bile acid concentrations, and subsequent histological examination of a liver biopsy will provide a definitive diagnosis.