Non-variceal Extrahepatic Portosystemic Shunts: A Review of Pathogenesis, Diagnosis, and Treatment.

Extrahepatic portosystemic shunts (EPS) are abnormal connections between the portal and systemic circulations. Acquired EPS occur most commonly in adults and are usually associated with portal hypertension due to cirrhosis. Acquired EPS cases can be further subdivided into two types: variceal (pre-existing) EPS and non-variceal EPS (NVEPS). Variceal EPS arise from originally small vessels with pre-existing dual portal and systemic drainage. Due to elevated portal pressure, these vessels dilate and undergo a reversal of flow, sending blood back to the systemic circulation. A much less common and, therefore, underappreciated subset of acquired EPS is NVEPS, which consists of aberrant connections that did not previously exist between the portal vein and large systemic vessels, usually in the presence of portal hypertension. Neoangiogenesis results in the development of abnormal anastomoses between the portal vein and other large veins, resulting in splenorenal, gastrorenal, portocaval, and mesocaval shunts. While not uncommon, they are frequently overlooked in the diagnosis and treatment of portal hypertension and can pose significant diagnostic and therapeutic challenges. Because the treatment of variceal EPS and NVEPS can differ markedly, it is important to correctly diagnose NVEPS and institute appropriate management. The aim of this article was to review acquired EPS, with particular attention to NVEPS, updating the pathogenesis, diagnosis, and treatment.