Sir: The flap congestion caused by inadequate venous drainage is the most frequent complication in retrograde flaps. Studies have been performed regarding venous drainage in the distally based peroneal flap and distally based superficial sural flap, and communicating channels and bypasses between the concomitant veins around the arteries have been demonstrated with venous drainage through these channels.1–3 I think that this concept can be adopted for the retrograde ulnar dorsal flap. In my experience, for the best result, one must leave a wide adipofascial pedicle to ensure the connections between arteries and veins (Figs. 1 and 2).Fig. 1.: Intraoperative view of the island retrograde ulnar dorsal flap. No large vein is included in the wide adipofascial pedicle.Fig. 2.: Photograph obtained on the third postoperative day. Good perfusion without venous insufficiency can be observed.A large vein inclusion into the flap, like that described by Dr. Altun et al. is not recommended by me. Xu and Lai-Jin observed that the lesser saphenous vein included in the pedicle of the distally based sural neurocutaneous flap is the cause of venous congestion, and they recommend ligating the lesser saphenous vein4: Based on our experience, we suggest the lesser saphenous vein cannot provide venous drainage to the distally based sural neurocutaneous flap; in contrast, the lesser saphenous vein is the direct cause of the postoperative venous congestion. In addition, this venous congestion due to preservation of the lesser saphenous vein is difficult to release. Due to its competent function in most cases, we consider the lesser saphenous vein is resistant to reverse flow.4 Probably the cause of flap congestion that is described by Altun et al. could have the same explanation. I do not have studies about the venous drainage in the retrograde ulnar dorsal flap, so I adopted the same concept for the distally based peroneal flap and distally based superficial sural flap. Enrique Vergara, M.D. Universidad Nacional de Colombia Ciudad Universitaria Carrera 30, Calle 45 Bogota 11001000, Colombia