Portosystemic shunts in dogs and cats: laboratory diagnosis of congenital portosystemic shunts

The most frequent laboratory abnormalities in patients with congenital portosystemic shunts (CPSS) are microcytosis, hypoglycemia, hypoalbuminemia, hypoproteinemia, increased liver enzyme activities, decreased blood urea nitrogen (BUN) and urate crystalluria. The microcytosis is probably due to impaired iron transport. Hypoglycemia, hypoalbuminemia, hypoproteinemia and decreased BUN are partly due to decreased hepatic synthesis. Prolonged coagulation times are also common. A presumptive diagnosis of CPSS is based on the combination of the history, clinical signs, clinicopathological abnormalities and abnormal liver function tests such as serum bile acid and venous ammonia concentrations. Nowadays, determination of preand postprandial serum bile acids is the most commonly performed liver function test because of the high sensitivity and greater convenience compared to plasma ammonia concentration. Confirmation of the diagnosis is only possible by visualizing the shunting vessel by medical imaging techniques or during surgery.