Ultrasonographic features of focal xanthogranulomatous pyelonephritis.

OBJECTIVE: To analyze the ultrasonographic features of focal xanthogranulomatous pyelonephritis. METHODS: Ultrasonographic features of 15 patients with pathologically proved focal xanthogranulomatous pyelonephritis were retrospectively analyzed by 2 radiologists who reached a consensus, in terms of the location, margin, size, and echo texture of the mass, associated calculi, lymphadenopathy, or local extension, in comparison with computed tomographic and clinical findings. RESULTS: At ultrasonography, 12 (80%) of 15 masses were well circumscribed. The maximal sizes of the masses ranged from 2.5 to 5.8 (mean, 3.8) cm. Thirteen solid masses (87%) were hyperechoic (n = 7), hypoechoic (n = 4), or isoechoic (n = 4) to the renal cortex, and the preoperative diagnosis was either renal cell carcinoma (n = 11) or Wilms tumor (n = 2). The preoperative diagnosis of the other 2 cystic lesions (13%) was renal abscess. Renal calculi were found in 1 case, but lymphadenopathy or local extension was not depicted. Clinical inflammatory signs were found in 11 of 15 patients. CONCLUSIONS: There were no specific ultrasonographic features that allow for the distinction between focal xanthogranulomatous pyelonephritis and renal tumors or abscesses. Focal xanthogranulomatous pyelonephritis should be considered when there are clinical signs of infection or inflammation and a focal solid mass is seen on ultrasonography.