[Renal tumor or pseudotumoral xanthogranulomatous pyelonephritis].

We here report the case of a 55 year-old man presenting with right renal colic and with a history of intermittent lower back disorders. At the time of admission, clinical examination showed lower back pain on contact. Renal ultrasound objectified heterogeneous mass at the lower pole of the right kidney with dilation of lower calyx groups. Abdominal CT scan confirmed the presence of right inferior renal polar lesion characterized by mixed density, associated with significant hydronephrosis eroding the renal parenchyma upstream of a voluminous pyelic coralliform lithiasis. The patient underwent nephrectomy with anatomo-pathological examination revealing chronic inflammation of the renal parenchyma characterized by macrophages associated with monocytes and lymphocytes with spongy cells and fibrosis. Anatomo-pathological result was compatible with a diagnosis of xanthogranulomatous pyelonephritis. Xanthogranulomatous pyelonephritis is a relatively rare chronic pyelonephritis whose symptoms resemble those of a pseudotumor. The diagnosis is suspected on the basis of clinical arguments and on laboratory tests and may be evoked quite exclusively on the basis of preoperative CT scan. Kidney cancer was its main differential diagnosis.