COLOR-ASSISTED COMPRESSION ULTRASOUND IN THE DIAGNOSIS OF CALF DEEP VENOUS THROMBOSIS

Objective: To determine and specificity of colour-assisted compression ultrasound (CUS) in the diagnosis of deep venous thrombosis (DVT) iso lated to the calf veins. Design: Prospective comparison of CUS with co ntrast venography in patients undergoing both procedures, with blinded evaluation of results. Setting: Alfred Hospital, Melbourne (an urban tertiary referral hospital), between November 1990 and May 1992. Subje cts: Patients presenting for contrast venography with signs or symptom s of lower limb DVT. Outcome measures: Presence of DVT; technical adeq uacy of examination. Results: 92 of 402 patients (104 limbs) were exam ined. DVT was detected by venography in 43 limbs and was isolated to t he calf veins in 19. It was diagnosed by CUS for eight of these 19. Ca lf CUS was technically inadequate in 26 limbs. Sensitivity and specifi city of CUS for isolated calf DVT were 67% (95% confidence interval [C I], 40%-94%) and 93% (95% CI, 83%-100%), respectively, when the CUS wa s adequate. The low sensitivity of CUS was related to small size of th e thrombi, inadequate studies because of previous DVT or very swollen limbs and technical errors. Conclusion: CUS is accurate for detecting larger isolated calf DVT when the calf study is adequate. Including th e calf veins as well as the femoropopliteal veins in the initial CUS e xamination for symptomatic suspected lower limb DVT may reduce the nee d for follow-up CUS.