Xanthogranulomatous pyelonephritis

Four cases of xanthogranulomatous pyelonephritis are reported, including one case previously diagnosed as renal carcinoma. Clinically, abdominal pain, weight loss and fever were the most common findings and, in every instance, a mass was palpated. Pathologically, the distinctive characteristic was a unilateral focal or diffuse replacement of the kidney and adjacent perirenal tissue by lipid-laden macrophages (foam cells) and, in 2 instances, multinucleated giant cells within areas of granulomatous reaction. Chronic suppurative nephropathy secondary to urolithiasis was noted in 3 cases. Nephrectomy was the treatment of choice and resulted in the relief of symptoms in all the cases. Although only 67 cases have been reported in the literature, it is probable that this figure does not reflect the true incidence of this condition. This lesion is important to recognize because it may be confused, both clinically and pathologically, with carcinoma of the kidney.