Diagnostic value of liver function tests and ultrasonography in dogs with suspected congenital portosystemic shunts.

Background: Diagnosing a congenital portosystemic shunt (cPSS) in dogs can be challenging. The current study aims to report diagnostic performance of fasting ammonia (FA), preprandial, postprandial and paired serum bile acids (SBA) and abdominal ultrasound (aUS) in dogs suspected of having a cPSS.

Methods: Medical records of dogs suspected of having a cPSS at initial presentation were retrospectively reviewed.

Results: In total, 192 dogs suspected of cPSS were included: a cPSS was confirmed in 147 dogs and excluded in 45 dogs. FA had the best combined sensitivity and specificity (77.4 and 93.3%, respectively) to diagnose cPSS. The sensitivity and negative predictive value were 100.0% for paired SBA, making paired SBA the best test to exclude cPSS in this population. Sensitivity and specificity of aUS were 80.8 and 90.0%, respectively.

Conclusions: In dogs with clinical signs compatible with cPSS, elevated FA is suggestive of cPSS, whereas normal paired SBA makes the presence of a cPSS unlikely. Although aUS is a useful tool to diagnose cPSS, additional imaging is required to visualize cPSS in almost 20% of cases. Furthermore, the localisation of cPSS can be misdiagnosed, especially in case of extrahepatic cPSS that do not insert into the prehepatic vena cava.