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The College of Veterinary Medicine

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Portosystemic Shunts


Postoperative Care

After surgery, animals are monitored closely for portal hypertension (shock, pain, abdominal distension), seizures, hypothermia, and hypoglycemia. Most animals will need some pain medication; oxymorphone is used most frequently. Sedation with a low dose (0.02 mg/kg IM) of ace promazine may be necessary if dogs are vocalizing or abdominal pressing, since these activities will increase portal pressure. Dogs with ameroid constrictor occlusion usually experience minimal discomfort.

Low protein diet and lactulose are continued after surgery until liver function improves. Frequently the animals can be gradually weaned off of the lactulose 4 to 6 weeks after the surgery. Bile acids and albumin are evaluated 2, 4, 6, and 12 months after the surgery to evaluate liver function. Protein in the diet can be gradually increased once bile acids are normal. In dogs with mildly elevated bile acids and normal albumin, it may be necessary to monitor clinical response to diet change to determine whether protein content can be gradually increased.

Treatment of postoperative portal hypertension includes intravenous fluid administration for hypovolemic shock, systemic antibiotics, and immediate surgery to remove the PSS ligature. Factors which may increase portal pressure postoperatively include excessive intraoperative fluid administration, increased systemic blood pressure from anesthetic recovery, and increased intra-abdominal pressure from bandages, pain, or vocalization.

Between 5 and 10% of animals develop seizures after shunt ligation. Seizures commonly occur in cats and occasionally in small breed dogs. No response is seen with administration of IV dextrose or enemas, and diazepam does little to control the seizures. Animals that develop seizures should be given a lactulose enema and placed on a slow continuous intravenous infusion of propofol (or another barbiturate) over 12-24 hours (.025 to 1.0 mg/kg/minute) to stop the seizures. Cats should also be treated with oral lactulose and neomycin when they are conscious.

Prognosis

Shunt occlusion should be avoided in animals with very low albumin (1.0 g/dL) or any other indication of severe liver disease, such as ascites or cirrhosis, since prognosis is poor for recovery from anesthesia in these animals.

Prognosis is better for dogs with extrahepatic shunts; for animals that undergo complete shunt ligation or occlusion with ameroid constrictors; and for those that present with urinary tract signs and no hepatic encephalopathy. Complication rates are much lower and the surgery is much faster when ameroid constrictors are used. In 50% of dogs undergoing partial shunt ligation with suture ligatures, further shunt attenuation is not necessary. Half of dogs that undergo partial shunt ligation with suture ligatures develop clinical signs of portosystemic shunting within 2 years after ligation. Half of these dogs either have multiple portosystemic shunts from portal hypertension or are unable to undergo further attenuation because of mildly increased portal pressure.

Cats often continue to have neurologic signs after surgery and may need to be placed on frequent doses of lactulose and neomycin (every 6 hours) or phenobarbital. Cats frequently develop recurrent clinical signs after undergoing partial ligation; it has been suggested that cats should undergo a second surgery for complete ligation one month after the initial surgery. Long-term, only one third of cats do well after shunt ligation.

 

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