Portosystemic Shunts

Pet Tales
by Barry B. Burtis D.V.M.

Looking back at Roosevelt's medical history, he probably showed the first symptoms of his disease when he was seven months old. Up until that time he had been a normal little male Schnauzer growing up in a home where he was loved and cared for by owners devoted to his well-being. Oh, he had gone through the usual "growing up pain" ailments experienced by most pups - an episode of diarrhea when he chewed some spoiled food he found in the backyard, some sore gums when losing his baby teeth - but no illness of any consequence. These problems were dealt with rather routinely as part of his health care when he visited the animal hospital to complete his vaccination requirements.

However, in the spring, just before he was a year old, Roosevelt was brought to see the veterinarian because he was acting quite different from normal. He was panting a lot, he seemed quite lethargic, he could not be stimulated, when encouraged to play. He had been gagging and coughing mildly for a few days. No specific cause for these changes could be found when Roosevelt was examined and some blood tests were recommended. These tests showed some elevation in two liver enzymes, rather unusual in a pup of this age.
Some adjustments were made in Roosevelt's diet and it was recommended those tests would need to be rechecked to determine whether further investigations would be required.

For the next 3 years Roosevelt enjoyed reasonably good health. Follow-up blood tests that were checked showed the abnormal liver enzymes remained above normal, at essentially the same level of elevation. Another test that could shed more light on how Roosevelt's liver was functioning was discussed with his owners. However, considering how well he was doing, that test was not performed, until Roosevelt suffered a more severe illness last spring. The blood test that was done at that time is called a serum bile acid test. It is quite a simple, non-invasive test to do. The patient has a blood sample collected after fasting for 12 hours. It is then fed a regular meal and 2 hours later another blood sample is collected. Bile acid levels, in the serum portion of the blood, are then measured in each sample.

Bile acids are produced in our bodies in the liver from cholesterol. After production they are stored in the gallbladder and enter the intestinal canal to assist in digestion - especially the digestion of fats in our diets. It is possible to get a better idea of how effectively the liver is actually working by learning how well it is performing its job with respect to levels of bile acids in the circulating blood. Roosevelt's bile acid levels were significantly abnormal. They indicated that he had significant liver disease and that the reason for his health problems was because this very important organ was failing. This meant that further tests would now be necessary to more specifically identify the reason his liver was sick. Dogs, as with other animals, can develop a number of diseases that will cause the liver to fail in this fashion. Chronic hepatitis, infectious hepatitis, cirrhosis, cancer and toxic hepatopathy are some such disorders. However, in a young dog like Roosevelt, there is one more condition that goes high on the list of possible causes - a congenital portosystemic shunt.

In this condition an animal is born with a malformation in the veins in or near the liver. This malformation prevents circulating blood from passing through the liver and being cleansed of toxic materials that it has picked up in the gut. In addition to problems caused by increased levels of these toxins in the body, eventually the liver, itself, will likely be more severely affected. This condition can affect both dogs and cats. Irish wolfhounds, Old English sheepdogs, cairn terriers, miniature schnauzers and Yorkshire terriers are the dog breeds most commonly affected. It is more common in mixed breed, rather than purebred cats.

Affected animals usually show a combination of central nervous system and gastrointestinal signs. Loss of appetite, lethargy, episodic weakness, pacing, loss of balance, head pressing and blindness, behaviour changes or even seizures may be seen when the nervous system is affected. Vomiting, diarrhea or a depraved appetite are gastrointestinal symptoms sometimes seen.

More diagnostic testing for a patient with liver problems like Roosevelt had, will likely involve imaging the liver. This means that x-rays and/or ultrasound images of the liver are needed. In many cases a biopsy of the liver will also be required. Sometimes an ultrasound guided needle biopsy can be used to collect representative liver tissue for assessment, other times it may be necessary to perform  exploratory surgery to examine the organ and collect biopsy samples. In some patients who have a portosystemic shunt, the abnormal blood vessels can be seen on ultrasound examination.

With these factors in consideration, Roosevelt was referred to an internal medicine specialist. An ultrasound examination performed showed the liver to be very small, a shunt outside the liver was identified and a number of small stones were found to be present in the urinary bladder. These stones are another common complication seen in patients with liver shunts. With the diagnosis confirmed, Roosevelt was taken to surgery. An ameroid constrictor was applied to the abnormal vessel in order to establish more normal blood flow through Roosevelt's liver. Liver biopsies were collected and the bladder stones were surgically removed. Roosevelt got along very well through his surgery and recovery. Adjustments were made in Roosevelt's diet and follow-up monitoring of his liver function will be done. Now with his birth anomaly corrected, hopefully, Roosevelt will be able to enjoy a good quality life for years to come.