3-dimensional volume rendered computerized tomography for preoperative evaluation and intraoperative treatment of patients undergoing nephron sparingsurgery

Purpose: Computerized tomography (CT) is the diagnostic and staging modalit y of choice for renal neoplasms. Existing imaging modalities are limited by a 2-dimensional (D) format. Recent advances in computer technology now all ow the production of high quality 3-D images from helical CT. Nephron spari ng surgery requires a detailed understanding of renal anatomy. Preoperative evaluation must delineate the relationship of the tumor to adjacent normal structures and demonstrate the vascular supply to the tumor for the surgeo n to conserve as much normal parenchyma as possible. We propose that helica l CT combined with 3-D volume rendering provides all of the information req uired for preoperative evaluation and intraoperative management of nephron sparing surgery cases. We prospectively evaluated the role of 3-D volume re ndering CT in 60 patients undergoing nephron sparing surgery for renal cell carcinoma at the Cleveland Clinic Foundation. Materials and Methods: Triphasic spiral CT was performed preoperatively in 60 consecutive patients undergoing nephron sparing surgery for renal neopla sms. A 3 to 5-minute videotape was prepared using volume rendering software which demonstrated the position of the kidney, location and depth of exten sion of the tumor(s), renal artery(ies) and vein(s), and relationship of th e tumor to the collecting system. These videotapes were viewed by a radiolo gist and urologist in the operating room at surgery, and immediately correl ated with surgical findings. Corresponding renal arteriograms of 19 patient s were retrospectively compared to 3-D volume rendering CT and operative fi ndings. Results: A total of 97 renal masses were identified in 60 cases evaluated w ith 3-D volume rendering CT before nephron sparing surgery. There were no c omplications related to the 3-D protocol and 3-D rendering was successful i n all patients. The number and location of lesions identified by 3-D volume rendering CT were accurate in all cases, while enhancement and diagnostic characteristics were consistent with pathological findings in 95 of 97 tumo rs (98%). Of 77 renal arteries identified at surgery 74 were detected by 3- D volume rendering CT (96%). Helical CT missed 3 small accessory arteries, including 1 in a cross fused ectopic kidney. All major venous branches and anomalies were identified, including 3 circumaortic left renal veins. Of 69 renal veins identified at surgery 64 were detected by 3-D volume rendering CT (93%). All 5 renal veins missed by CT were small, short, duplicated rig ht branches of the main renal vein. Renal fusion and malrotation anomalies were correctly identified in all 4 patients. Conclusions: The 3-D volume rendering CT accurately depicts the renal paren chymal and vascular anatomy in a format familiar to most surgeons. The data integrate essential information from angiography, venography, excretory ur ography and conventional 2-D CT into a single imaging modality, and can obv iate the need for more invasive imaging. Additionally, the use of videotape in an intraoperative setting provides concise, accurate and immediate 3-D information to the surgeon, and it has become the preferred means of data d isplay for these procedures at our center.