The goal of nephron-sparing renal surgery is complete surgical excision of a renal mass with preservation of a sufficient amount of functional renal parenchyma to avoid the need for dialysis following surgery. Thirty-three percent of all renal masses are now detected incidentally during the cross-sectional evaluation of the abdomen or retroperitoneum for nonrenal indications (1,2). The traditional indications for performing nephron-sparing renal surgery have expanded to include these incidentally detected, small, asymptomatic renal tumors, and the results have been favorable (2,3). The increased use of nephron-sparing surgical procedures has prompted the need for a more comprehensive preoperative radiological definition of renal neoplasms. The surgeons need information to assist them in determining the feasibility of performing nephron-sparing surgery, plan the surgical procedure, and ensure that complete surgical excision of the renal neoplasm is possible.

The cases presented illustrate the use of 3D helical CT imaging for preoperative radiological evaluation before nephron-sparing renal surgery. The helical CT protocol used by the authors is outlined in Table 1 (Somatom Plus 4; Siemens Medical Systems, Iselin, NJ, U.S.A.). Two 3D CT displays (i.e., arterial phase and venous phase displays) are created for each patient using volume-rendering technique (prototype version of 3Dvirtuoso; Siemens Medical Systems). Arterial phase 3D CT displays are used for defining the mass and arterial anatomy, and the venous phase images are used to evaluate venous anatomy and, if present, renal venous invasion. The 3D helical CT images display the renal mass in innumerable imaging planes and orientations, providing important preoperative information that is necessary to plan nephron-sparing renal surgery. The 3D helical CT display localizes the renal mass and defines its relationship to the renal surface, perinephric structures, renal hilum, renal arteries, and renal veins. A 3D helical CT angiogram, created within seconds from the 3D CT display, defines the renal arterial and venous anatomy (4,5). The 3D helical CT display can be viewed in both standard and stereoscopic modes of display as stereo display. Stereoscopic viewing is useful for determining 3D relationships and for evaluating complex vascular anatomy (6). The 3D CT display can easily be oriented to display the renal mass in an anatomic fashion or one that stimulates the surgical perspective. Real-time interaction provides the radiologist and urologist with a flexible and unique perspective of a renal mass that is unavailable with axial helical CT imaging (7).