Norma, sounds like Klippel-Trenaunay Syndrome. The book states the a-v fistulas are microscopic type communicators, may be hard to see. Hope this helps. Carol Vandenberg, RN, RVT Norma VandenBerghe wrote: > I have a question about using duplex US to identify and localize > congenital arterio-venous malformations. I have had a few cases through > the years, and have not really had much luck with tracking the little > devils down. I have been able to predict a couple of intracranial cases > based on the differences between the flow signals in the two carotid > arteries. But in the extremities, as on the child I saw today with > hugely distended veins and even small venous ulcerations on his left > leg, they have remained elusive. I looked at the entire arterial system > for low resistance or turbulence; I looked at the entire venous system > for arterialized flow, pulsation, etc. And found nothing. No > difference compared to the same site on the unaffected right leg. I > looked at iliacs and all the way down the leg. I tried to just look for > abnormal color flow. I looked with velocity scale set high. Set low. > Gain up, down etc. Nothing. > > Have others had more success than I have? I feel like I must be > overlooking something. > Thanks! Norma V.