Incidence of pre-operative deep venous thrombosis in abdominal surgery.

In order to determine the incidence of pre-operative and postoperative deep venous thrombosis (DVT) in patients not receiving prophylactic anticoagulant therapy, bilateral phlebography was performed in a prospective study pre-operatively and on the 9th postoperative day, in 51 consecutive patients submitted for major abdominal surgery. The presence of a DVT before surgery was demonstrated in 15.7 per cent of the patients. This high frequency confirms objectively the rationale of starting prophylactic anticoagulant therapy before the surgical procedure. Thrombi were demonstrated postoperatively by phlebography in 54.9 per cent of the patients. Thus the true incidence of DVT induced by surgery was 39.2 per cent taking into account the 15.7 per cent pre-operative DVT rate.