[Xanthogranulomatous pyelonephritis. Value of magnetic resonance imaging].

Xanthogranulomatous pyelonephritis is a rare disease which frequently has a pseudotumoral appearance. Preoperative diagnosis is hazardous in spite of ultrasonography and CT scan correlation. Recently developed magnetic resonance imaging (MRI) identifies fatty tissue which is specific for XGP. The frequency of invasive investigations has decreased because of this new data and partial nephrectomy has become possible in localized forms of XGP. Magnetic resonance imaging provides an accurate reproduction of the lesions in three dimensions which allows detection of complications (abscess and fistulae) and a study of resection difficulties.