Fig. 4.

44-year-old woman with small oncocytoma demonstrating segmental enhancement inversion.

A. On coronal corticomedullary phase CT, renal mass at right kidney upper pole can be segmented into two areas. Crescent-shaped area at right aspect (white arrow) is more enhanced compared with relatively round shaped portion (black arrow) with heterogeneous enhancement at left aspect. Note adjacent medulla (arrowhead) at lateral aspect of renal mass which is less enhanced compared with well enhancing portion of renal mass. B. On coronal early excretory phase CT, enhancement degree of aforementioned two segments of renal mass is reversed. While previously more enhanced right crescent-shaped area (white arrow) is now less enhanced, round portion at left aspect (black arrow) shows marked enhancement, consistent with segmental enhancement inversion. Note that corticomedullary phase hypodense area and early excretory phase hyperattenuating area (arrowhead) are not part of mass but adjacent medullary tissue.