Ischemia of mesenteric arterial origin is far more frequent than that of venous disease. It is now recognized that many reported cases of mesenteric vein thrombosis in actuality represented incorrectly diagnosed cases of nonocclusive ischemia. The true incidence of mesenteric vein thrombosis is quite low. Although the etiology of acute mesenteric vein thrombosis may be idiopathic, the thrombosis is usually secondary to another disease process. Conditions that predispose to mesenteric vein thrombosis are (1) severe intra-abdominal sepsis, (2) hypercoagulable state (i.e., polycythemia vera) and (3) portal venous stasis (secondary to portal hypertension associated with hepatic cirrhosis, or to extrinsic compression of the venous system secondary to a tumor mass).

Thrombosis of the superior or inferior mesenteric vein alone is usually not sufficient to produce intestinal ischemia. However, acute thrombosis in a large mesenteric vein has the potential to cause retrograde propagation of the clot up into the venous tributaries within the bowel wall. This resultant venous occlusion within the bowel wall will usually produce ischemia, possibly with infarction. In many cases of venous intestinal ischemia the thrombosis does not begin in a large mesenteric vein. In these situations it appears that the venous thrombosis begins primarily in the small venous intramural tributaries. In either case, if the venous thrombosis becomes extensive, arterial thrombosis may follow, making it very difficult to determine the exact etiology of the intestinal ischemia.

The clinical presentation of patients with venous intestinal ischemia is often similar if not identical to that of patients with acute mesenteric artery occlusion. Accordingly, the diagnosis is often made only at the time of surgery or by the pathologist who examines the resected specimen.

The treatment of this disease is generally surgical, with the infarcted segment of intestine being resected. The surgeon should be aware that the venous thrombosis may extend beyond the limits of the gross infarction. Since any residual thrombosis has the potential to propagate, the resection should include adjacent bowel and mesentery until all grossly involved thrombosed veins are removed. It has been shown that mortality from this disease can be reduced if patients are anticoagulated as soon as possible after surgery.