What is the most common cause of sinistral portal hypertension?

Sinistral portal hypertension, also known as left-sided portal hypertension, primarily results from conditions affecting the splenic vein, which drains blood from the spleen and the pancreas into the portal vein. The most common cause of sinistral portal hypertension is chronic pancreatitis.

Chronic pancreatitis can lead to the development of peripancreatic fibrosis and scarring, which can compress the splenic vein and subsequently elevate the pressure within the portal venous system. This increase in pressure is specifically noted in the veins draining the left side of the portal system, leading to symptoms associated with sinistral portal hypertension, such as splenomegaly and varices isolated to the left side of the body.

While other conditions such as cirrhosis, portal vein thrombosis, and hepatic tumors can cause portal hypertension, they typically lead to more generalized portal hypertension rather than the localized effects seen with sinistral portal hypertension. Chronic pancreatitis is notably linked with changes in the anatomy and blood flow characteristics in the splenic vein, making it a distinctive cause in this context.