Pediatric xanthogranulomatous pyelonephritis masquerading as complex renal mass.

We present a case of focal xanthogranulomatous pyelonephritis (XGP) in a pediatric patient. This case illustrates the variable presentation of the entity and the difficulty in making a preoperative diagnosis. In contrast to the usual diffuse form of XGP, the focal form permits less radical treatment in cases such as this one.