Replacement lipomatosis of the kidney: CT features.

Replacement lipomatosis of the kidney is a severe loss of renal parenchyma with massive fat deposition associated with long-standing inflammation and calculi. We report two pathologically proven cases of total replacement lipomatosis and one partial replacement lipomatosis diagnosed by CT. The CT images demonstrated a large fat-attenuating mass with perirenal capsule surrounded by thick pararenal fascia, streaky densities in the mass, elongated collecting system, large calculi, and absence of renal parenchyma.