Xanthogranulomatous pyelonephritis

CT scan of xanthogranulomatous pyelonephritis with perinephric extension. There is diffuse enlargement of the left kidney and the renal tissue is replaced by multiple low-attenuation masses (arrow). A calcification is visible within the renal pelvis and there is posterior and pararenal extension of the pseudotumoral inflammatory tissue. The contralateral kidney is normal.