Incidence of portosystemic shunts in Finnish miniature schnauzer litters

Congenital portosystemic shunts (CPSSs) are vascular anomalies that permit communication between the portal and systemic circulation, thus allowing venous blood to bypass the liver. Previous studies have reported an estimated CPSS prevalence of 0.18-0.76% in the general dog population, being more commonly diagnosed in purebred breeds such as cairn terriers, Maltese, dachshunds, Yorkshire terriers, Irish wolfhounds, golden retrievers and Labrador retrievers. In addition, miniature schnauzers are known to be predisposed to CPSSs, but the breed-specific incidence has not been systematically investigated. This study was undertaken to evaluate the incidence of CPSSs in Finnish 6-12-week-old miniature schnauzer puppies within a one-year study period. The puppies were screened for the presence of a CPSS by measuring the postprandial serum bile acid (SBA) concentration. When the SBA concentration was above the reference limit, further investigations were performed (i.e., pre- and postprandial bile acid stimulation test, computer tomography (CT) or post-mortem examination). Based on the results, the incidence of CPSSs was calculated.

The study included 582 dogs from 121 litters, representing 58% (582/1004) of the miniature schnauzers born and registered in Finland during the 1-year study period. In screening, an elevated postprandial serum SBA concentration was presented in 3.3% (19/582) of the dogs. In retesting with the SBA stimulation test 1-4 weeks later, 11 of these 19 dogs had pre- and postprandial bile acid concentrations within the reference range and were excluded from further investigations. One dog with elevated SBA concentrations was diagnosed with portal vein hypoplasia and seven dogs with a CPSS. In addition, one dog had a normal postprandial SBA concentration at screening but was later diagnosed with a CPSS as an incidental finding by CT. In summary, a CPSS was diagnosed in 8/582 dogs and the incidence was 1.37%. All diagnosed CPSS vessels originated either from the splenic vein (n = 5) or the left gastric vein (n = 3) and inserted into the caudal vena cava at the level of the diaphragm.

The incidence of the congenital portosystemic shunts in Finnish miniature schnauzers was elevated when compared to the estimated prevalence in the general dog population. The morphology of the portosystemic shunts could indicate a common genetic background.