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If Your Pup Starts Going Downhill, A Portosystemic Shunt May Be The Culprit

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Your 5-month-old golden retriever, who came home with you as a happy, healthy puppy, doesn't seem to be growing as fast as he should. In addition, he has no get-up-and-go, and he doesn't wolf down his puppy chow like he used to. He's just not the same dog. A phone call to your vet yielded a word you've never heard before, but it sounded scary: portosystemic shunt. Here is some basic information about this condition so you know what questions to ask the doctor when you bring your pup in for a diagnosis.

What Is a Portosystemic Shunt?

According to the American College of Veterinary Surgeons, a portosystemic shunt (PSS) is an abnormal connection between the portal vein and systemic circulation. In a normal puppy, blood from the abdominal organs enters the portal vein which transports it to the liver for detoxification. In a dog with PSS, the blood is shunted to the systemic circulation without first going to the liver. The shunt allows substances such as ammonia to build up in the bloodstream, which can be toxic to vital organs. It also deprives the liver of the nutrients it needs to grow normally, resulting in liver atrophy.

There are 2 main types of PSS: congenital and acquired. Within those 2 categories are the subcategories: extrahepatic (outside the liver) and intrahepatic (inside the liver). Extrahepatic congenital PSS occurs mostly in small breeds, such as yorkies, cairn terriers and maltese. Intrahepatic congenital PSS is found mainly in large breeds such as labs, golden retrievers, and Old English Sheepdogs

Congenital PSS means it was present at birth and is by far the most common type. It is usually diagnosed before a dog is 6 months old, which is about the time the stunted liver can no longer provide the filtration needed to keep up with the dog's growth.

Acquired PSS occurs later in the dog's life. It is usually associated with liver disease or hepatic hypertension and often causes numerous tiny shunts around the liver.

What Are the Symptoms?

A puppy with PSS will almost always show signs before 1 year of age, but in milder cases, symptoms may not show up for years. Common symptoms include stunted growth, lethargy, loss of appetite, poor muscle development, distended belly, disorientation, staring into space, head pressing, and seizures.

How Is PSS Diagnosed?

A complete history of the onset of symptoms and behavior changes is a key tool for diagnosing PSS. Your vet will also likely do a CBC and blood chemistry panel to check liver enzyme levels. A bile acid test checks for bile acid, which is usually elevated in dogs with PSS. Other diagnostic measures include ultrasound, MRI, CT scan or nuclear scintigraphy -- a nuclear scan that measures blood flow through the liver. One of the most effective tools is portography, which uses contrast dye to outline the liver shunt.

How Is PSS Treated?

The most effective treatment is surgery to close the shunt. However, your pup must be stabilized before surgery is performed. This requires feeding them a low protein diet, such as a liver prescription diet, and administration of lactulose, which prevents ammonia from entering the blood stream. Antibiotics also decrease the production of ammonia. Anti-convulsive medications may be needed to control seizures.

After the dog is stabilized, your vet or specialist will perform a procedure to close the shunt. Usually this is done by using a device called an ameroid constrictor rather than actual cutting and sewing. The constrictor is placed around the shunt and over a period of 3 to 4 weeks, slowly closes the shunt. Depending on how large and how numerous the shunts are, the prognosis is excellent for a long and healthy life.

For more information, contact your local vet clinic