Superior Mesenteric and Portal Vein Thrombosis Caused by Congenital Antithrombin III Deficiency: Report of a Case

A 50-year-old man presented with a 24-h history of gradually worsening abdominal pain. Enhanced computed tomography showed segmental dilation of the small intestine, wall thickening, and ascites, as well as thrombosis of the superior mesenteric vein (SMV) and portal vein. Thus, an emergency laparotomy was performed, which revealed segmental intestinal infarction caused by the thrombosis in the SMV and portal vein. We resected the necrosed intestine and performed anastomosis. The patient was given intravenous heparin and nafamostat mesilate as anticoagulation therapy. The abdominal pain again recurred 4 days after this operation, necessitating a second laparotomy. Segmental congestion of the intestine was found and another resection was done, after which he recovered rapidly. Blood chemistry subsequently revealed an antithrombin III deficiency, which was confirmed to be inherent, after screening his family. Thus, laboratory testing for these proteins may help define the cause of mesenteric venous thrombosis.