Xanthogranulomatous pyelonephritis in childhood

Purpose: Demographic data, clinical presentation, associated abnormalities, and radiologic findings were evaluated to outline diagnostic criteria that may lead to the diagnosis of xanthogranulomatous pyelonephritis in childre n. Methods: Eleven boys and 8 girls with a mean age of 3.4 +/- 1.7 years were classified into obstructive xanthogranulomatous pyelonephritis (n = 13), wh ich was associated with nephrolithiasis and nonobstructive (n = 6), which m imicked Wilms' tumor. Results: Twelve children with obstructive diffuse involvement of the renal parenchyma, 1 with left-sided obstructive focal involvement in a horseshoe kidney (group 1), and 6 with nonobstructive diffuse xanthogranulomatous pye lonephritis (group 2) showed a male to female ratio of 1.2:1 and 2:1, respe ctively. Mean age was 4.1 +/- 1.2 years in group 1 versus 1.8 +/- 1.5 years in group 2; P = .001. The common features were renal mass, hematuria, and anemia (100%; P = .07) and leucocytosis (77% v 83%; P = .097). Main differe nces between the 2 groups were acute inflammatory syndrome (0 v 33%; P = .0 1), recurrent urinary infection (54% v 17%; P = .05), isolation of Proteus mirabilis as a pathogen (69% v 0; P = .001), and renal stones(100% v 0; P = .001). Preoperative diagnosis was accurate in all 13 (100%) children with obstructive xanthogranulomatous pyelonephritis. Radiologic features that we re not consistent with Wilms' tumor in group 2 were absence of sharp defini tion and encapsulation of the mass, ill-defined margins with inflammatory i nfiltration of the perinephric fat and focal inflammatory tissue destructio n. Nephrectomy was technically difficult because of extensive adhesions to the retroperitoneum, psoas muscle, and surrounding structures in both group s. Conclusions: Xanthogranulomatous pyelonephritis must be considered in the d ifferential diagnosis of a child presenting with a renal mass, anemia, and elevated inflammatory markers. Treatment by nephrectomy is curative.