Antithrombin III deficiency causing postsplenectomy mesenteric venous thrombosis coincident with thrombocytopenia.

The most commonly recognized cause of mesenteric venous thrombosis following splenectomy is hypercoagulation secondary to reactive thrombocytosis. A case is reviewed in which hypercoagulation followed splenectomy for idiopathic thrombocytopenic purpura (ITP) in spite of persistent thrombocytopenia. Episodic mesenteric venous occlusion occurred due to antithrombin III deficiency. This hypercoagulable state may be the cause of primary acute mesenteric venous occlusive disease. Symptoms and signs suggesting thrombosis in the portal circulation demand immediate coagulation studies since even in the thrombocytopenic patient thrombotic proglems can occur. Surgical intervention is the treatment of choice for segmental small bowel ischemia; warfarin therapy is indicated when there is evidence of antithrombin III deficiency.