Clinical significance of routine imaging of iliac and calf veins by color flow duplex scanning in patients suspected of having acute lower extremity deep venous thrombosis.

BACKGROUND: Because duplex ultrasonography is used increasingly to evaluate patients suspected of having acute deep venous thrombosis of the lower extremity, the clinical significance of limiting venous duplex scanning to the common femoral, superficial femoral, and popliteal veins becomes an important question.

METHODS: We prospectively studied by venous color flow duplex ultrasonography 181 patients referred for evaluation to rule out acute deep venous thrombosis to determine (1) the frequency with which the iliac and calf veins could be imaged adequately to determine the presence or absence of acute deep venous thrombosis, (2) the frequency of acute venous thrombosis in these venous segments, and (3) the time required to scan these additional segments.

RESULTS: In 79% of the patients studied, one segment of the iliac venous system was imaged adequately to determine the presence or absence of venous thrombosis. In the lower extremity, the common femoral vein, the superficial femoral vein, and the popliteal vein were imaged adequately in 94% of the patients. In 76% of the patients all three calf veins were imaged adequately to determine whether acute deep venous thrombosis was present or absent. The anterior tibial vein was the most difficult vein to image consistently and was imaged adequately in 76% of the patients referred. The mean time to scan the affected limb was 8 minutes 37 seconds. Forty-seven patients (26%) of the 180 patients studied had positive venous scans. Twenty-three percent of the patients who had positive scans were found to have iliac vein involvement. Thirty-two percent who had positive venous scans were found to have thrombosis of the calf veins. Fifteen percent of the 47 patients who had positive scans had either an isolated iliac or calf vein thrombosis.

CONCLUSIONS: We believe this frequency of isolated iliac or calf vein thrombosis coupled with the frequency of successful imaging of these venous segments and the short additional time required to image these segments justifies the inclusion of routine imaging of the iliac and calf veins in patients undergoing venous duplex scanning to rule out acute deep venous thrombosis.