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. This case, however, did not exhibit any of the usual features of XGP reported in large series, making preoperative planning problematic.