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Porto Systemic Shunt

 

This condition is often referred to as a "liver shunt" but the current favored term appears to be portosystemic shunt. It has also been referred to by more exact terms, since there are specific types of shunts that vary slightly. The broad categories are extrahepatic and intrahepatic shunts, depending on whether or not the shunt occurs in the liver or outside of it. Specific types of shunts are patent ductus venosus, portal-azygous, portocaval (portal-abdominal vena cava), atresia (lack of development) of the portal vein and acquired shunts that occur due to changes in blood pressure or circulation.

Most shunts cause recognizable clinical signs by the time a dog is a young adult but occasionally, one is diagnosed at a later time in life. Since the severity of the condition can vary widely depending on how much blood flow is diverted past the liver, it is possible for a lot of variation in the clinical signs and time of onset of the signs to occur. Often, this condition is recognized after a puppy fails to grow, making an early diagnosis common.

Signs of portosystemic shunts include poor weight gain, sensitivity to sedatives (especially diazepam), depression, head pressing (pushing the head against a solid object), seizures, weakness, salivation, vomiting, poor appetite, increased drinking and urinating, balance problems and frequent urinary tract disease or early onset of bladder stones. If the signs of problems increase dramatically after eating this is a strong supportive sign of a portosystemic shunt.

It is frustrating, since there isnšt one specific test for this condition. Although, there almost is one - special dyes are injected into the liver circulation, showing up on X-rays and can usually outline the problem pretty clearly. However, this is a pretty invasive test, making it a poor choice for "screening" purposes. There are a number of possible abnormalities that might point towards a portosystemic shunt on routine labwork, including low BUN (blood urea nitrogen), low albumin, mild anemia, increases in ALT (serum alanine aminotransferase) or ALKP (serum alkaline phosphatase). If these signs were present, it would be a good idea to test the serum bile acid levels prior to eating and after eating. If this test is supportive of poor liver function then it may be a good idea to consider ultrasonagraphy and dye contrast X-rays.

At the present time, Hepatic Porto-Systemic shunts are considered to be UNQUESTIONABLY genetic by some of the leading canine experts, but the mode has not been identified at the present time; research is being conducted at Michigan State University to identify this pattern.