Failure of microvenous valves in small superficial veins is a key to the skin changes of venous insufficiency

ObjectiveTo determine the role of microvenous valves in the superficial venous system in the prevention of reflux and skin changes in the progression of venous insufficency.MethodsThe venous anatomy of 15 amputated lower limbs, eight free from clinical venous disease and seven with varicose veins and ulcers, was examined using retrograde venography corrosion casting. Prior to amputation, all limbs were scanned by duplex ultrasound to confirm the presence or absence of reflux in the great (GSV) and small saphenous veins or their tributaries. The resulting resin casts were photographed and mapped to show the position, orientation, and competency of valves in the superficial venous network. Casts were also examined by scanning electron microscopy.ResultsRetrograde venous filling was demonstrated in the “normal” limbs despite a competent GSV. Microvalves were identified down to the sixth generation of tributaries from the GSV. Only in regions where incompetence existed in microvalves out to the third (ie, the “boundary”) generation was the resin able to penetrate deeper into microvenous networks of the dermis. This was despite the presence of subsequent competent valves, which were able to be bypassed in the network. In limbs with varicose veins and venous ulcers, reflux into the small venous networks and capillary loops was more extensive with more dense networks and greater tortuousity.ConclusionsThis study demonstrates that valvular incompetence can occur independently in small superficial veins in the absence of reflux within the GSV and the major tributaries. We have shown that once there is incompetence of the third generation “boundary” microvalves, reflux can extend into the microvenous networks in the skin. These effects are markedly worse in the presence of GSV incompetence. We propose that degenerative changes with valve incompetence are required in both the larger proximal vessels and the small superficial veins, in particular at the “boundary” valve level, for the severe skin changes in venous insufficiency to occur.Clinical RelevanceThis study describes the presence of microvalves in the very small veins in the skin, which may be critical to whether skin changes occur in venous insufficiency. The concept may explain why some people with longstanding varicose veins do not develop venous ulcers. In addition, this article describes degenerative changes in the network of very small veins in the skin of the leg which may relate to appearances of reticular veins, corona phlebectatica, and venous flares. These degenerative changes occur without varicose veins but are much worse when they occur together