Superior Mesenteric Vein

vena mesenterica superior

The superior mesenteric vein drains the small intestine, right colon, and transverse colon. It ascends to the right of the superior mesenteric artery, crosses anterior to the third part of the duodenum, and joins the splenic vein behind the neck of the pancreas to form the portal vein. It is a large vein that can be identified at operation by its position to the right of the SMA.

Region: Abdomen

Clinical Relevance

Clinical Notes

The superior mesenteric vein is the primary drainage of the midgut and is a component of the portal venous system. SMV thrombosis causes acute mesenteric venous ischaemia with abdominal pain, bloody diarrhoea, and bowel necrosis, seen in hypercoagulable states, portal hypertension, and post-abdominal surgery. In pancreaticoduodenectomy (Whipple procedure), assessing SMV involvement by tumour determines resectability: tumour abutment or encasement of the SMV-portal vein confluence is a key staging criterion for pancreatic head cancers.

Pathology

Common Injuries & Conditions

Superior Mesenteric Vein Thrombosis

Thrombosis of the SMV from hypercoagulable states, portal hypertension, or abdominal surgery causes subacute intestinal venous congestion progressing to infarction, presenting with progressive abdominal pain and requiring anticoagulation and surgical resection of infarcted bowel.