Errors in the differential diagnosis of incompetence of the popliteal vein and short saphenous vein by Doppler ultrasound.

Doppler Ultrasound is now routinely used to demonstrate valvular reflux in the venous system. Incompetence detected at the back of the knee is located either in the short saphenous vein or in the popliteal vein. Whether the incompetence is in the deep or superficial venous system can be differentiated by digital compression over the short saphenous vein in the upper calf; if reflux is abolished then the incompetence is assumed to be in the superficial vein but if it is not prevented it must be in the popliteal vein. Sometimes the reflux is not controlled when the deep system is normal. This has been shown to be due to variations in the anatomy of the short saphenous vein and especially the pattern of its termination. Examples with venography are given, showing that in the presence of incompetence at the sapheno-popliteal junction there may be no reflux in the short saphenous vein; instead the proximal tributaries are involved and reflux in these veins is not controlled by pressure over the short saphenous vein. This explains the false positive diagnosis of valvular incompetence in the popliteal vein.