Most dogs will be diagnosed with port-systemic shunts under one year of age, but dogs as old as eight have been diagnosed with the condition. In most affected dogs there will be some degree of behavioral signs ranging from listlessness, apathy, or depression to more severe signs of circling, head pressing, stupor, drooling, blindness, or convulsions, some leading to coma. Even anti-convulsants used to control seizures may be potentially dangerous if allowed to concentrate in a dog with functional shunt. There can be bladder stones formed or crystals may be noted on the hair around the prepuce or vulva. The uric acid levels may be elevated in a significant number of affected individuals.
Acid levels are extremely important in the diagnostic screening of symptomatic potential shunts.
Fasting and 2-hr. In virtually all porto-systemic shunts there will be a significant rise in the bile acid levels over normal. Reports of recent vaccination with modified-live vaccines causing high serum bile acid levels in normal animals have not been confirmed as of this time. This procedure also does not identify the exact location of the shunt for surgical correction if required. Until recently, ultrasound was fairly unreliable for nonsurgical diagnosis of porto-systemic shunts.