Hepatic Vascular Malformations in Small Dog Breeds: Gastroenterology What the Textbooks Don't Tell You

Introduction Extrahepatic portosystemic vascular anomalies (PSVA) in small breed dogs, originally described in the 1970s, have received notorious attention in the veterinary literature. We estimate that this congenital malformation comprises approximately 0.6 to 2.0% of a specialty hospital patient population. However, microvascular dysplasia (MVD), a genetically related hepatic vascular disorder is far more common; 15 to 30:1 compared to the prevalence of PSVA in affected kindreds based on investigations in an expansive genotyping initiative. MVD occurs as a single entity or coexists with PSVA. Unfortunately, discovery of high serum bile acid concentrations in dogs with MVD often leads to expensive and invasive diagnostic assessments for PSVA in pet dogs. Dogs affected only with MVD are typically asymptomatic and their hepatic vascular abnormalities non-progressive. The majority of dogs affected only with MVD do not need medical treatments as assigned for dogs with symptomatic PSVA and have a normal life expectancy. Many MVD affected dogs are discovered on the basis of high serum bile acid concentrations revealed upon screening kindreds for PSVA or serendipitously at the time of non-related illnesses. Misconceptions regarding management of MVD has caused confusion among clinicians, breeders of commonly affected small pure breed dogs, and pet dog owners.