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.