[Xanthogranulomatous pyelonephritis: presentation of an unusual case].

Introduction: Xanthogranulomatous pyelonephritis is a morphologically and clinically unique manifestation of chronic pyelonephritis with the formation of pus or granulomas. The most frequent predisposing factors for the development of xanthogranulomatous pyelonephritis are urinary obstruction (e. g., stones, tumors, congenital anomalies and functional impairment) and infection of the collecting system.

Case Report: We describe a 2-year-old female patient with unclear abdominal complaints, diarrhea, malaise, loss of appetite, weight loss, pale skin color, and recurrent and undulating fever in the presence of known left nephrolithiasis. Based on the clinical examination and imaging, above all, CT, the presumptive diagnosis of xanthogranulomatous pyelonephritis of the left kidney was made. A left lumbar nephrectomy was performed and histology confirmed the diagnosis.

Conclusion: Xanthogranulomatous pyelonephritis is a relatively rare entity that is associated with obstruction (e. g., stones) and infection of the urinary tract. Its rarity and resultant unfamiliarity often delay diagnosis and therapy, which in turn affect the prognosis. Furthermore, this entity can be mistaken for renal tumors (renal cell carcinoma and Wilms tumor), but nowadays this should be mostly eliminated with the advances in the imaging methods.