Deep venous thrombosis: Detection by using indirect CT venography

PURPOSE: To assess the clinical benefits of performing indirect computed to mographic (CT) venography after pulmonary CT angiography to detect deep ven ous thrombosis (DVT) in patients suspected of having a pulmonary embolism. MATERIALS AND METHODS: The authors prospectively enrolled 541 consecutive p atients who underwent pulmonary CT angiography for suspected pulmonary embo lism at seven institutions. Using a protocol that optimizes venous enhancem ent without additional contrast material injection, the authors obtained co ntiguous images from the pelvis to the popliteal fossa. Ultrasonography (US ) also was performed in 116 patients. RESULTS: DVT was found at indirect CT venography in 45 (8%), and pulmonary embolism was found at pulmonary CT angiography in 91 (17%) of 541 patients. Among the 45 patients with DVT, DVT occurred in 16 patients who had no pul monary embolism at pulmonary CT angiography, which increased the diagnosis of thromboembolic disease by 18%. Among 116 patients who underwent US and i ndirect CT venography, 15 had DVT at US, and in ail 15, DVT also was seen a t indirect CT venography. In four additional cases, DVT was seen at only in direct CT venography. CONCLUSION: Among patients suspected to have pulmonary;embolism, a substant ial number had DVT in the absence of pulmonary embolism. Combined pulmonary CT angiography-indirect CT venography can depict these cases with accuracy comparable to that of US and thus could have a significant effect on patie nt care.