Microvascular Dysplasia Mimics Portosystemic Shunt

Microvascular dysplasia (MD)is a disease in which the patients have abnormal, microscopic communications between the portal and systemic venous systems within the liver parenchyma. These microscopic shunt vessels allow the portal blood to escape normal filtration by the liver parenchyma, similar to a traditional, portosystemic shunt.

Breeds affected with MD are similar to traditional shunts, with the Yorkshire terrier, Schnauzer and Poodle over represented. Clinical signs and laboratory abnormalities of patients with MD are similar to those of the traditional portosystemic shunt patients. However, as a general rule, the severity of the clinical signs and changes in lab values is less in MD patients.

A defintive diagnosis is established by liver biopsy and eliminating the possibility of a macrovascular shunt either by exploratory surgery or nuclear scintigraphy. Treatment is nonsurgical and aimed at minimizing signs of hepatic encephalopathy, along with supporting liver function.