Splanchnic Venous Thrombosis

Abdominal veins bring blood lacking oxygen from the abdomen to the inferior vena cava, draining to the right atrium. Abdominal organs have 2 venous systems: the systemic one, which drains directly to the inferior vena cava, and the portal one, which drains to the hepatic portal vein and then to the inferior vena cava through the liver. The systemic venous system includes common iliac, lumbar, renal, right testicular/ovarian, right suprarenal, inferior phrenic, and hepatic veins. The portal venous system includes right and left gastric, cystic, para-umbilical, splenic, inferior mesenteric (via a splenic vein), and superior mesenteric vein. The splenic and superior mesenteric merge to form the portal vein. Blood clotting in these venous systems can lead to splanchnic venous thrombosis; this includes thrombosis in the splenic, mesenteric, portal, or hepatic veins (eg, Budd-Chiari syndrome). The most common site of venous thrombosis is a portal and mesenteric vein, with the least common being the hepatic vein. Splanchnic venous thrombosis can lead to different symptoms depending on the site of the thrombosis.