We have previously reported that the decrease in gastric mucosal blood flow (GMBF) and consumption coagulopathy (CC) mainly contribute to the development of postoperative bleeding in the upper gastrointestinal (GI) tract in patients with abdominal aortic aneurysm (AAA). In the present study, we investigated whether our treatment for patients with low GMBF or CC effectively prevented postoperative gastric bleeding induced by gastric ulcer or acute gastric mucosal lesion. Preoperative endoscopic examinations in 66 patients with AAA and 60 patients with arteriosclerosis obliterance (ASO) revealed that 50.0% of AAA and 16.6% of ASO patients had accompanying gastric ulcer or multiple erosions. In 38 AAA and 36 ASO patients, GMBF was measured using a laser Doppler flowmeter through an endoscope. The GMBF was severely impaired in AAA patients and moderately impaired in ASO patients. The platelet counts and fibrinogen levels were significantly decreased in these 38 AAA patients compared with controls. Furthermore, fibrinogen degeneration product (FDP) levels in 36.8% of AAA patients were more than 20 micrograms/dl. Based on these findings, patients with low GMBF were treated postoperatively with H2-blocker, and patients with CC were treated preoperatively with heparin. After these treatments, only 1 of 38 AAA patients developed postoperative upper GI tract bleeding and could be treated conservatively after 1988, whereas in prior years postoperative upper GI tract bleeding developed in 7 of 112 patients, three of whom required emergency surgery.