Portosystemic (Liver) Shunts
A portosystemic or liver shunt is an abnormal blood vessel in the abdomen that skips over the liver instead of passing through it for detoxification of blood. The blood continues to circulate substances that would normally be removed, such as ammonia, mercaptans, and other products taken in through the gastrointestinal tract. These substances have access to the brain, g.i. tract, heart, and other organs and affect the pet in multiple ways. Signs often observed include seizures, mentation changes, aggression, stupor, head pressing, vomiting, diarrhea, weight loss, failure to thrive, pica (eating strange objects like dirt, mineral, foreign objects), etc.
PSS can occur primarily outside the liver (EHPSS Extrahepatic Portosystemic Shunt) or inside the liver (IHPSS Intrahepatic Portosystemic Shunt). Extrahepatic is more common in small breed it’s such as Pugs, Maltese, Chihuahuas, Yorkies. Intrahepatic can occur in larger breeds like Labradors and Standard Poodles.
Full bloodwork, clinical signs and history are often highly suggestive for a shunt. Once a shunt is suspected, a serum bile acids test will be performed to see if the liver if capable of removing the patient’s own bile salts after a small meal. If the bile acids are consistent with a shunt, an abdominal CT scan will be reformed to actually view to the shunting vessel and help plan the surgery.
At surgery, the vessel is located and gently isolated. A device called an Ameroid Constrictor is placed around the vessel and secured to surrounding tissue. The Ameroid inside the steel band will slowly constrict over several weeks time, gently directing the blood flow back through the normal vessels and through the liver. This happens on a slow and gradual basis to avoid any chance of shock and to decrease patient risks. Many pets lead normal lives after this procedure.
There are situations where an Ameroid Constrictor cannot be used. The main contraindication is the patient with multiple acquired shunts. These form secondary to severe liver disease. They cannot be attenuated or constricted because the liver is unable to accept normal blood flow.
The same applies to a patient with end stage cirrhotic change as the over cannot accept normal blood flow.
There is also a condition where pets are born with multiple congenital (extrahepatic) shunts. These also cannot be constricted due to number and the underlying liver pathology.
In rare conditions, we may suspect a PSS Ned have inconclusive CT findings. In those cases, an abdominal exploratory is recommended. All PSS patients have a liver biopsy taken for prognosis, so this I performed here as well. If nor PSS is found, he liver biopsy usually confirms a diagnosis known as MVD Microvascular Dysplasia. This is simply microscopic PSS within the liver itself. Some pets with an EHPSS may have a minor degrees or MVD too, other have only MVD and a PSS is no present. MVD is manage medically and some patients can do quite well. You Dr. will spread to you in email about the treatment options if MVD is the biopsy diagnosis.