Contrast venography in patients with very edematous feet: use of transdermal illumination to aid in vein puncture. Contrast venography can be technically difficult or impossible in patients with very edematous feet. The authors report a simple technique that uses transdermal illumination of the edematous subcutaneous tissue to enable visualization of a vein and also guide the needle into the vein. This technique has been used successfully in eight patients in whom conventional attempts at vein puncture had failed. 