Arteriovenous fistulae (AVF) occur after percutaneous renal biopsy in up to 18% of patients. Fistulae may remain asymptomatic or lead to hematuria, hypertension, and/or renal insufficiency. The identification of an AVF has traditionally been made with angiography; however, ultrasonography, which is less invasive and nonnephrotoxic, has become a valuable tool in the localization of a postbiopsy fistula. Most postbiopsy AVF are asymptomatic and close spontaneously. Conversely, AVF may enlarge and

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... become symptomatic, requiring embolization to reverse or prevent complications. A case of renal insufficiency in a renal transplant recipient due to a postbiopsy AVF is presented. Spontaneous closure of the AVF resulted in the resolution of renal insufficiency. One must suspect an AVF when renal insufficiency occurs in an allograft after biopsy. Further study is needed to identify ultrasound characteristics that will predict the natural history of postbiopsy AVF.