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A comparison of preoperative long saphenous phlebography with operative dissection in assessing the suitability of long saphenous vein for use as a bypass graft.

A technique for assessing the anatomy and luminal diameter of the long saphenous vein by direct injection phlebography in patients being considered for reversed femoropopliteal vein bypass surgery is described. In 25 consecutive patients, 20 single veins, four double veins and one network of veins were all correctly delineated by this technique and subsequently confirmed at operation. Five saphenous veins could not be demonstrated above the knee but at operation one vein was found to be present and double from knee to groin. The minimum mean luminal diameter of the saphenous vein estimated from the X-ray after correction for magnification was 3.5 mm +/- 1.12 which was significantly less than the mean external diameter found at operation, 4.6 mm +/- 1.33 (P less than 0.001). The vein diameter found at operation invariably proved to be larger than the luminal diameter estimated from the X-ray. This allows a confident preoperative assumption of the minimum diameter that will be obtained after dissection and distension of the vein.