Focal xanthogranulomatous pyelonephritis presenting as renal tumour in children. Case report with a review of the literature.

Xanthogranulomatous pyelonephritis (XGP) is a specific form of chronic inflammatory kidney disease which may involve both sexes at any age. The disease presents either in the diffuse form or less commonly as a focal process which is almost impossible to differentiate from renal malignancy. XGP usually occurs in association with urinary tract obstruction, infection and/or renal stones. Symptoms are often vague and non-specific. The most common offending organisms are E. coli and Proteus mirabilis. In reviewing the literature we have found 197 cases in children during the last thirty years, and of these only 15 (7.6%) were of the focal form. A case of focal xanthogranulomatous pyelonephritis in a 6-year-old boy is reported which demonstrates the diagnostic difficulties encountered in this disease. We emphasize the importance of XGP in the differential diagnosis of renal tumours in children with recurrent or therapy-resistant urinary tract infection in spite of no evidence of renal stone, poorly or absent function in the kidney or urinary tract obstruction.