Diameters of acute proximal and distal deep venous thrombosis of the lower limbs.

BACKGROUND: Duplex ultrasonography of the veins in the diagnosis of deep venous thrombosis (DVT) can be interpreted in a semi-quantitative mode by measuring the antero-posterior (AP) diameter of the thrombus. We report the values of the diameters of thrombi and the factors influencing these values. Therefore we propose a quantitative definition for DVT in duplex ultrasonography.

METHODS: 1,017 patients (3,767 thrombosed venous segments), referred to the Emergency Angiology Unit from January 1994 to September 1996. Characteristics: 55% F, 45% M; mean age 68+/-18 years; 624 proximal DVT (61%) and 393 distal DVT (39%). Measurement by venous echography of the antero-posterior diameters of thrombi at 25 predetermined sites in the area of the vena cava.

RESULTS: (In mm, median, 10th and 90th percentiles after regrouping of contiguous anatomical sites not statistically different): thrombus in the common iliac veins and the inferior vena cava (12 mm, 7-17); external iliac and common femoral veins (9 mm, 5-14); superficial femoral, deep femoral and popliteal veins (6 mm, 4-10); calf veins (5 mm, 4-8). The age of the patients, their sex, body mass index (BMI), whether they were in- or outpatients or the laterality of the thrombus never significantly influenced its diameter.

CONCLUSIONS: It is very unusual to observe a diameter of under 5 mm in cases of DVT. For clinical research therefore, we propose 5 mm as the minimum threshold value for this diagnosis. This value could be used in the venous echographic definition of DVT, as a criterion for inclusion in a therapeutic trial, for example, or in an epidemiological study.