Liver shunts, also called portosystemic shunts, are abnormal veins that enable blood from the intestines to bypass the liver. Ammonia and other toxins are not metabolized or removed from the circulation, resulting in signs of hepatic encephalopathy.
Most dogs with congenital liver shunts develop symptoms of hepatic encephalopathy by 6 months of age, although some dogs may not develop symptoms until middle-age or older.
The majority of portosystemic shunts are congenital. Multiple shunts outside the liver may be congenital but are more often caused by cirrhosis. Dogs of a variety of breeds have been identified with liver shunts, but Miniature Schnausers, Maltese, and Yorkshire Terriers appear to be at increased risk for congenital shunts that develop outside the liver. Large breed dogs such as Irish Wolfhounds, are at increased risk for shunts inside the liver that occur due to a fetal vein that normally closes at birth that fails to do so.
The diagnosis is confirmed by X-ray studies where contrast dyes are injected into the liver circulation, and by bile acid assays. Ultrasound may also be useful. These studies are available at referral centers.
The treatment of choice for liver shunts is partial or complete surgical ligation of the shunt. This is not always possible. Medical management is directed toward controlling hepatic encephalopathy.
Dogs with liver shunts should not be bred.
Please contact your veterinarian for more information regarding this condition.
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