Portosystemic Shunt (Hepatic Shunt) in Cats
Dr. Erika De Papp
Surgical ligation of the shunt is the preferred treatment. However, animals may need to be medically stabilized before they are good candidates for anesthesia and surgery. In some cases it may not be possible to close the shunting vessel completely; this depends on its location. This is most often a problem in large breed dogs. If surgery is not an option, medical management is the mainstay of therapy. Medical treatment may include: Intravenous fluid therapy. Patients may be dehydrated and have electrolyte imbalances and/or hypoglycemia due to vomiting, diarrhea, or not eating and drinking normally. IV fluids are important to correct metabolic disturbances prior to any invasive procedures.
Lactulose. This is a laxative drug that causes acidification of the gut contents in the colon. The acidity causes ammonia to be trapped in the colon, thereby preventing absorption of ammonia into the bloodstream. This helps lower the blood ammonia levels in patients with hepatic encephalopathy.
Antibiotics. Antibiotics are often given orally to alter the type of bacteria normally present within the intestines. Certain types of bacteria cause ammonia production. By reducing these bacteria with antibiotic therapy, there is less ammonia production. Antibiotic therapy is often used in combination with lactulose therapy.
Protein restriction. Prescription diets that are low in protein or homemade diets are recommended for patients with shunts. High protein content can exacerbate hepatic encephalopathy.
Gastric protectants. Drugs that are designed to reduce stomach acidity can be beneficial for animals with shunts, especially if they are showing signs of gastrointestinal upset. Examples of these drugs include H2 blockers such as cimetidine (Tagamet®), famotidine (Pepcid®) and ranitidine (Zantac®). Another drug class that is a potent inhibitor of stomach acid production is the proton pump inhibitors. Omeprazole (Prilosec®) is an example of this type of drug. Sucralfate (Carafate®) is a third class of stomach protectant that binds to stomach ulcers. One or more of these drugs may be useful in alleviating some of the gastrointestinal signs seen in patients with shunts.
Anti-convulsant medication. Hepatic encephalopathy is often responsive to treatment with fluid therapy, lactulose, and antibiotics. In cases that are not responsive to these drugs, anti-convulsant drugs may be needed to control seizure activity. Examples of this drug class include phenobarbital and potassium bromide.
Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not rapidly improve.
Immediately following surgery your pet will remain hospitalized for several days. Complications following surgical correction of the shunt may include portal hypertension and worsening of neurologic abnormalities. Portal hypertension is an elevation of blood pressure in the portal vein. This can occur after surgery and can result in reduced blood flow to other abdominal organs. This in turn may cause abdominal fluid accumulation, vomiting, diarrhea, abdominal pain and in severe cases, shock. New methods of repairing the shunting vessel have minimized this complication. Animals may also develop seizures following surgery, even if they did not have them pre-operatively. This requires anticonvulsant therapy and in-hospital monitoring.
Once your pet is discharged from the hospital, careful monitoring at home will be necessary. Observation of seizures, anorexia, vomiting, abdominal distension, or abnormal behavior should prompt a call to your veterinarian.
Administer all prescribed medications as directed. Alert your veterinarian if you are having problems treating your pet.
Feed only the prescribed diet. Although your pet may eventually be able to eat a normal diet, protein restriction may be necessary for an extended time period or even for life.
After hospital discharge, your pet should be re-examined by your veterinarian in 10 to 14 days. At that time the surgical sutures (stitches) will be removed and a physical exam will be performed to evaluate clinical progress. Even if your pet seems to be doing well at home, a careful exam may reveal subtle neurologic abnormalities.
Follow-up bloodwork, especially bile acids, can be used to assess improvement in liver function following surgical correction of the shunt. These results often do not return to normal, but are expected to improve after surgery. In certain cases the shunt may not be fully closed at the first surgery. The degree of improvement in clinical signs and lab results may dictate whether a second surgery is needed in the future.
Monthly evaluations for the first several months after surgery are important for keeping track of your pet's progress.
Many pets can do very well after shunt repair, but it is important to keep a close relationship with your veterinarian for the life of your pet, as this is a complicated and serious disorder.