BACKGROUND Hemodialysis access thrombosis is a significant cause of morbidity for hemodialysis patients and results from decreased access flow caused by venous outflow tract stenosis. Ultrasound dilution (UD) is a practical, noninvasive, and reliable indicator of access flow and is effective in predicting venous stenosis in adult patients receiving hemodialysis. METHODS The current study is the first to our knowledge to evaluate the accuracy of UD in predicting hemodialysis access stenosis in a pediatric hemodialysis population. Thirteen pediatric patients receiving hemodialysis via permanent access (4 AVF and 9 AVG) received 73 UD measurements over three months. RESULTS Mean raw access flow (QA) was 720 +/- 428 mL/min, and mean corrected access flow (QAcorr) was 886 +/- 537 mL/min/1.73 m(2). QAcorr was significantly lower in accesses with stenosis (401 +/- 176 mL/min/1.73 m(2)) versus accesses without stenosis (1158 +/- 330 mL/min/1.73 m(2), P < 0.0001). Unlike flow values reported by raw QA, there was no overlap in flow values reported by QAcorr in accesses with stenosis (174 to 579 mL/min/1.73 m(2)) versus accesses without stenosis (709 to 1711 mL/min/1.73 m(2)). Two patients with an AVG who had QAcorr less than 600 mL/min/1.73 m(2) developed an access thrombosis within one week after UD measurement. No patients with QAcorr greater than 700 mL/min/1.73 m(2) developed access thrombosis in the 30 days following UD measurement. CONCLUSIONS : The current study supports the use of monthly UD measurement to prevent access thrombosis in children receiving hemodialysis.