Colour Doppler flow imaging ultrasonography versus venography as screening method for asymptomatic postoperative deep venous thrombosis

Objective: To evaluate colour Doppler flow imaging ultrasonography (CDFI), compared with venography, as a screening method for postoperative deep venous thrombosis (DVT) in a clinical trial on thromboprophylaxis. Methods: Patients undergoing major abdominal or thoracic surgery were prospectively screened for DVT by CDFI. Patients were examined preoperatively, and on postoperative days 1, 3, 7, 14, 21, and 28. When the CDFI was positive venography was performed. Bilateral venography was performed on day 28 in all patients. The study group comprised 82 patients who underwent CDFI and venography on the same day: four because of suspected DVT (positive CDFI), and 78 on day 28 according to protocol. Results: DVT was detected by venography in seven patients, in three of whom CDFI was positive. CDFI was falsely positive in one case. There were two popliteal and five calf DVTs, of which CDFI detected one and two, respectively. The sensitivity of CDFI was 43%, the specificity 99%. The PVpos for CDFI was 75%, and the PVneg 96%. Conclusion: Due to low sensitivity, CDFI cannot stand alone as a screening method for asymptomatic postoperative DVT.