Access recirculation in a native fistula in spite of a seemingly adequate access flow

True access recirculation (AR) measured by ultrasound dilution technique is usually absent in well-working shunts. It occurs with low access flows (Qa ), High access flow rates are assumed to prevent AR. Two major exceptions t o these rules are known: presence of intra-access strictures acid inadverte ntly reversed blood lines. We present an additional exception in which true access recirculation occurred in a native arteriovenous (AV) fistula with correct placement of bloodlines. Surprisingly, access blood flow exceeded p ump blood flow (Qb) almost threefold. The situation was clarified by a magn etic resonance angiogram showing a collateral forming a functional loop. Th is loop led to true access recirculation in one branch, although overall bl ood flow through both branches appeared to be adequate. The different findi ngs in this shunt over time give insight into the often complex pathophysio logy of native fistulae, This case proves that seemingly adequate access fl ow does not necessarily prevent access recirculation in native AV fistulae, We suggest monitoring both access flow and recirculation in hemodialysis a ccesses on a regular basis. (C) 2000 by the National Kidney Foundation, Inc .