['The aim of this study was to determine the role of antithrombin III (AT-III) in portal vein thrombosis (PVT) after splenectomy in cirrhotic patients.', 'There is no standard treatment for PVT after splenectomy in liver cirrhosis.', 'A total of 50 consecutive cirrhotic patients who underwent laparoscopic splenectomy for hypersplenism were enrolled into this study. From January 2005 to December 2005, 25 cirrhotic patients received no prophylactic anticoagulation therapy after the operation (AT-III [-] group). From January 2006 to July 2006, 25 cirrhotic patients received prophylactic administration of AT-III concentrates (1500 U/d) on postoperative day (POD) 1, 2, and 3 (AT-III [+] group).', 'In AT-III (-) group, 9 (36.0%) patients developed PVT up to POD 7, and risk factors for PVT were identified as: low platelet counts, low AT-III activity, and increased spleen weight. Although there were no significant differences in the clinical characteristics, including the above risk factors, between the 2 groups, only 1 (4.0%) patient developed PVT on POD 30 in AT-III (+) group, and the incidence of PVT was significantly lower than in AT-III (-) group (P = 0.01). In AT-III (-) group, AT-III activity was significantly decreased from POD 1 to POD 7, as compared with the preoperative level, whereas AT-III concentrates prevented the postoperative decrease in AT-III activity.'] Does impact of antithrombin III concentrate on portal vein thrombosis after splenectomy in patients with liver cirrhosis and hypersplenism?