abnormal vascular pathways that carry blood from the portal vein into circulation throughout the body without being filtered through the liver.
Properly functioning portal veins carry blood from the stomach, intestines, pancreas and spleen to the liver. In the case of a shunt vessel, the liver is prevented from filtering and processing the blood of toxins and is deprived of needed pancreatically-produced substances. Thus a portosystemic shunt results in an underdeveloped liver that cannot effectively synthesize, metabolize, or detoxify.
There are two broad classifications of Portosystemic shunts derived from the location of the shunt vessel either contained within or outside the liver proper. Extrahepatic shunts can be single or multiple vessels that are located completely outside the liver and are more common in cats, miniature and small breed dogs. Most commonly congenital (present at birth), extrahepatic shunts can also develop as a result of chronic liver disease. Intrahepatic shunts, located within the liver proper, are congenital and more common in larger breeds of dogs.
- Early onset (puppies)
- Slower than normal growth (smaller than they should be)
- Poor muscle development and hair coat
- Quiet demeanor (not playful like puppies)
- Behavioral abnormalities including circling & frequent disorientation, these changes are most often seen after eating
- Difficulty recovering from anesthesia or sedatives
- Abnormal liver function values
Less common symptoms include:
- Excessive drinking and/or urinating
- Excessive salivation is commonly seen in cats
Depending on the severity of clinical signs, a veterinary patient with a portosystemic shunt may need to be hospitalized to stabilize or control seizure activity. The surgical procedure for correction employs the use of either a vessel-constricting titanium ring or cellophane banding with the goal being to reduce blood flow through the shunted vessel, while redirecting the blood through healthy vessels and on to the liver.
Intrahepatic shunts may be best corrected with a staged attenuation procedure.
Following Portosystemic shunt surgery, close behavior monitoring and blood chemistry testing can help track progress.
The prognosis for animals with portosystemic shunt attenuation is good. In most cases clinical signs are eliminated and the patients do not require medical therapy. It is very uncommon for blood chemistry values to return completely to normal values.