Liver shunts affect dogs and cats. When an animal is wired correctly, blood that is absorbed from the gastrointestinal tract courses through the liver on its way to join the rest of the circulatory system. The liver serves as the body's security force, prohibiting entry to substances too toxic to enter circulation. In the uterus, the mother's liver does this work for the fetus, but once the kitten or puppy is born, the circuitry is typically re-wired so that the neonate's own liver starts doing this.
When this re-wiring does not occur, the animal has a liver shunt. Certain breeds have an increased risk of liver shunts, including Cairn and Yorkshire terriers, Maltese and Irish Wolfhounds on the canine side and Himalayan and Persians on the feline side.
If the liver is bypassed, toxins build up in the blood. This causes a wide variety of signs that usually start to become evident early in the young animal's life. Since the shunt can be complete, in which all of the intestinal blood bypasses the liver, or partial, where only some of it does, signs vary in severity based on the degree of shunting.
Pacing, wandering, spaciness, apparent blindness, stunted growth, vomiting, diarrhea and excessive thirst and urination all can be seen. Severely affected animals may progress to having full-blown seizures. Owners may observe that symptoms are worse after the animal eats a meal.
Blood work and clinical signs can provide a reasonable suspicion of a shunt, but definitive diagnosis of a liver shunt often requires advanced imaging so that the abnormal blood flow can be visualized. Sometimes, even imaging can't afford us with a definite diagnosis. So if an animal is symptomatic and blood work suggests a shunt, surgery is recommended to make the diagnosis and hopefully repair the problem.
The most common repair technique is to identify the shunt visually during surgery and then apply a small band, often made of cellophane, around the vessel. Over the course of a few weeks, the band constricts slowly putting the shunt out of business.
This might sound simple, but often there are multiple vessels involved and visual identification can be difficult. Because of this, patients are often referred to a board-certified veterinary surgeon for this procedure. Most patients improve after surgery, many achieving completely normal liver function and most improve at least some.
If it is suspected that the degree of shunting is mild, based on blood work or clinical signs, medical management centering on diet and medications designed to absorb toxins in the GI tract before they reach circulation often is at least somewhat effective. When a shunt is suspected in a very young animal, the prognosis is very poor without surgery. Conversely, if the animal is an adult when the shunt is discovered, signs can be mild and respond well to medical management for some time.
Christie Long is a veterinarian at the VCA Fort Collins Animal Hospital. Reach her at (970) 204-4567. Once a month, she will answer questions from her readers regarding pet health issues. Send e-mail to email@example.com
The Coloradoan, November 19, 2009
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