RESUMEN
Focal xanthogranulomatous pyelonephritis is an atypical form of chronic renal infection. It is frequently misdiagnosed preoperatively because of its resemblance to malignancy. We report on a fifty-year-old woman who presented with a right kidney mass. The CT scan showed a solid renal mass with a lithiasis of the upper ureter. The diagnosis of focal xanthogranulomatous pyelonephritis was suspected by clinical and radiological findings and confirmed by histopathologic examination of percutaneous biopsy specimens of the lesion. Successful treatment of the patient was achieved with removal of the lithiasis and antibiotic therapy during eight weeks. Three months later the CT scan was completely normal. The conservative treatment of focal xanthogranulomatous pyelonephritis makes possible to avoid a needless nephrectomy usually on young patients. However a close follow-up must be undergone on these patients because of the possible association of focal xanthogranulomatous pyelonephritis and renal cell carcinoma of the kidney