The superior mesenteric vein (SMV) collects blood from the small intestine, cecum, ascending colon, and transverse colon, running parallel to and to the right of the superior mesenteric artery. It joins with the splenic vein to form the portal vein, usually behind the neck of the pancreas — this confluence is an important anatomic landmark on abdominal ultrasound. The SMV is evaluated for thrombosis, which can present acutely with abdominal pain and bowel ischemia, or chronically with portal hypertension and collateral vessel formation. On ultrasound, SMV thrombosis appears as echogenic material within the vein lumen with absent or reduced Doppler flow. Dilation of the SMV can be a sign of portal hypertension or distal obstruction.
Sonography Term