RETROGRADE FLOW IN THE DEEP VEINS OF SUBJECTS WITH NORMAL VENOUS FUNCTION

Background Duplex ultrasonography has become the optimal non-invasive method of assessing the deep venous system of the leg. The stimuli use d to promote reverse flow, subject positioning, and the veins scanned have varied between studies. Reverse flow of less than 0.5 s is accept ed as 'normal', however, all published studies have demonstrated 'norm al' subjects with deep vein reverse flow exceeding this time. The aim of this study was to establish the duration of reverse flow in all dee p vein segments, and to determine the optimal method of eliciting reve rse flow in individuals with proven normal deep vein function. Methods Duplex scanning was used to detect the presence and duration of rever se flow in the superficial femoral, popliteal and posterior tibial vei ns of 61 legs with normal venous function. The veins were scanned with each subject inclined at 10 degrees, 45 degrees and standing erect. T he abrupt release of distal tourniquet compression and the Valsalva ma noeuvre were used as stimuli for reverse flow. Results There was signi ficantly less reverse flow in distal veins than in proximal veins when the subject was scanned at 10 degrees and 45 degrees. Median (range) reverse flow in the femoral vein at 10 degrees was 0.21 (0-1.18) s, po sterior tibial vein 0.08 (0-0.67) s, (P <0.0001); in the femoral vein at 45 degrees was 0.14 (0.04-2.14) s, posterior tibial vein 0.07 (0-0. 56) s, (P <0.0001). The duration of reverse flow was significantly les s in the superficial femoral and popliteal veins when the subjects wer e erect than when inclined at 10 degrees and 45 degrees. Median (range ) reverse flow in the femoral vein at 10 degrees was 0.21 (0-1.18), an d when standing 0.1 (0-1.36) (P <0.0001); below-knee popliteal vein at 10 degrees was 0.15 (0.04-1.95) s, and when standing 0.10 (0-1.03) (P =0.0004). Reverse flow of more than 0.5 s was never elicited in the po sterior tibial veins if the subject stood, nor did it occur in the pop liteal vein during a Valsalva manoeuvre. Conclusion The optimal sites to assess deep vein reverse flow are the posterior tibial vein followi ng removal of distal compression with the patient standing, and the po pliteal vein during a Valsalva manoeuvre, as retrograde flow more than 0.5 a does not occur in subjects with normal venous function.