Ultrasonography and needle aspiration in diagnosis of xanthogranulomatous pyelonephritis.

Xanthogranulomatous pyelonephritis may present as a renal mass which can be difficult to differentiate from a hypovascular renal tumor by intravenous pyelography or selective renal angiography. Four patients are described in whom ultrasonography with or without fine-needle aspiration suggested or confirmed the diagnosis of xanthogranulomatous pyelonephritis.