Diagnosis of Portosystemic Shunts
Nuclear scintigraphy is a noninvasive means of evaluating dogs for portal venous shunting. In dogs 99mtechnetium pertechnetate is extracted from the circulation primarily by the liver. In animals with shunts, the pertechnetate rapidly circulates to the heart and lungs. Normal dogs have a shunt fraction of less than 15% on scintigraphy; most dogs with shunts have fractions greater than 60%.
Magnetic resonance angiography (MRA) and CT scans have also been used to diagnose portosystemic shunts.
The ultimate diagnostic tool is laparotomy. Once experience is obtained, most extrahepatic shunts and approximately half of intrahepatic shunts can be identified on exploratory.