Postoperative thromboembolic complications despite heparin prophylaxis in major abdominal surgery

181 patients who received low-dose heparin prophylaxis in connection with major abdominal surgery were screened for postoperative thromboembolism by means of the 125 I-fibrinogen uptake test, venography and ventilation/perfusion lung scans. Among a number of potential risk factors analyzed only colonic surgery and preoperative anaemia were associated with significantly increased risk of postoperative thromboembolism.