As UMOD accumulation within renal tubules has been reported during normal neonatal development, we investigated UMOD expression in neonatal kidneys after unilateral ureteral obstruction (UUO) thereby linking a potential accumulation of UMOD at extratubular sites to leukocyte infiltration, which is commonly observed in neonatal UUO (40, 49). This evidence concerns the gene UMOD and Ureteral obstruction.