Xanthogranulomatous pyelonephritis: clinical experience with 41 cases.

Objectives: Xanthogranulomatous pyelonephritis (XGP) is an uncommon inflammation of the renal parenchyma that occurs in the presence of chronic obstruction and suppuration. In this retrospective study, a review of the features of 41 recent cases of XGP is presented and compared with current published data.

Methods: We retrospectively evaluated the clinical, surgical, and radiologic features of 41 cases of XGP and compared the data of this Brazilian population with that from current published reports.

Results: XGP was diagnosed in 19.2% of all nephrectomies performed for pyelonephritis during the period analyzed. Of the 41 patients with XGP, 85.4% were women and 14.6% were men. All patients were symptomatic, and the most common symptoms were fever, flank or abdominal pain, weight loss, lower urinary tract symptoms, and gross hematuria. The most frequent computed tomography findings included hydronephrosis, kidney enlargement, poor excretion of contrast medium, and air in the urinary tract. All patients had renal calculi, 34.1% of which were staghorn calculi. All patients underwent nephrectomy. For the few cases in which laparoscopy was performed, the conversion rate was high.

Conclusions: XGP is a common histologic variant of surgically managed pyelonephritis, corresponding to almost 20% of such cases. As described in other series, we found a population that largely consisted of middle-age women. The clinical presentation was characterized mainly by pain and constitutional symptoms. The main etiologic agent isolated was Escherichia coli, and in all cases, calculi were present. Computed tomography can be considered the best imaging study to diagnose XGP, and in the few cases managed by laparoscopy, high conversion rates were observed.