Modified Differential Renal Function Measurement Revised by Renal Cross Sectional Area in Children with Ureteropelvic Junction Obstruction

PURPOSE: Diuretic (99m)Tc-diethylenetriaminepentaacetic acid (Tc-DTPA) renal scans may show false-negative or false-positive results in children with ureteropelvic junction obstruction (UPJO). We evaluated whether modified differential renal function (DRF) revised by the renal cross-sectional area on imaging study may be a more valuable predictor than conventional DRF on a renal scan for deciding on a proper interventional time. MATERIALS AND METHODS: Between September 2001 and January 2008, we reviewed the diuretic renal scan results of 29 pediatric patients who underwent pyeloplasty due to unilateral UPJO. Diuretic renal scans using the standard (99m)Tc-DTPA protocol and imaging studies for renal unit measurement area were done. Conventional DRF measurement and modified calculation of DRF per unit area were done. Conventional DRF was classified into group I (below 40%) and group II (above 40%). RESULTS: The mean age of all patients was 42.6±52.6 months (range, 3-198 months). The mean cross-sectional areas of the UPJO kidney and of the normal contralateral kidney were 62.1±29.2 cm(2) and 41.3±22.5 cm(2), respectively (p<0.01). The conventional and modified DRF of the UPJO kidney were 45.2±9.2% and 35.2±9.5%, respectively (p<0.01). Thirteen children (62%) in group II (n=21) were classified in group I by the modified DRF measurement. CONCLUSIONS: The modified DRF measurement calculated according to cross-sectional area showed fewer false-negative results and may be a valuable method for deciding on pyeloplasty under equivocal circumstances.