Venous duplex scanning of the leg: range, variability and reproducibility.

Despite the many studies on venous haemodynamics using duplex, only a few evaluated the normal values, variability and reproducibility. Therefore, the range and variability of venous diameter, compressibility, flow and reflux were measured. To obtain normal values, 42 healthy individuals (42 limbs, 714 vein segments) with no history of venous disease were scanned by duplex. To determine the reproducibility the intra-observer variability was measured in 11 healthy individuals (187 vein segments) and the inter-observer variability in 15 healthy individuals (255 vein segments) and 13 patients (169 vein segments) previously diagnosed with deep venous thrombosis. Of the 714 normal vein segments, 708 (99%) were traceable, including the crural veins. Of the traceable vein segments, 675 (95%) were compressible and in 696 (98%) flow was present. Of the 42 common femoral vein segments, in 25 (60%) the reflux duration exceeded 1.0 s, but in the other proximal vein segments the reflux duration was less than 1.0 s (95% confidence interval 3.0-10.0). With the exception of the distal long saphenous vein, in the distal vein segments the reflux duration was less than 0.5 s (95% confidence interval 3.5-8.2). The coefficient of variation of the diameter measurements ranged from 14 to 50% and that of the reflux measurements from 28 to 60%. The kappa-coefficient of the inter-observer variability in the classification of compressibility measurements in the patients was 0. 77 and that of the reflux measurements was 0.86. This study shows that almost all veins were compressible in healthy individuals, except the distal femoral veins. In healthy individuals the duration of reflux of the proximal veins was less than 1.0 s and in the distal veins it was less than 0.5 s. The inter-observer variability of the reflux and compressibility measurements in the patients was good.