JOURNAL OF ENDOUROLOGY Volume 18, Number 6, August 2004 © Mary Ann Liebert, Inc. Virtual Endoscopy in Renal Artery Stenosis: An Innovative Approach for Diagnosis and Follow-Up GEORGE A. BARBALIAS, M.D., 1 EVANGELOS N. LIATSIKOS, M.D., 1 DIMITRIOS SIABLIS, M.D., 2 GEORGE C. KAGADIS, Ph.D., 3 THEODOROS PETSAS, M.D., 2 ANASTASIOS ATHANASSOPOULOS, M.D., 1 GEORGE NIKIFORIDIS, Ph.D., 3 and GRANNUM SANT, M.D. 4 ABSTRACT Purpose: We investigated the utility of virtual endoscopy (VE) as a diagnostic and follow-up tool in patients with renal artery stenosis, especially as a means of defining vascular patency. Patients and Methods: We performed VE in 24 patients with ostial atherosclerotic renal artery stenosis and correlated the results with those of conventional angiography. The patients were treated successfully by place- ment of metal stents and conventional catheter angiography and VE for patency assessment 6 and 12 months after stent insertion. Results: In all patients, the stenotic segment was identified, and VE findings were concordant with those of angiography. The average degree of stenosis was estimated to be 70%  20% when angiography was used and 62%  15% when VE was used. After metal stent insertion, the 12-month patency rate was 83.3% (20 patients). Angiography and VE findings remained concordant during the follow-up period, but VE provided more information beyond the stenotic segment, allowing examination of the arterial lumen both cephalad and caudal to the point of obstruction. Conclusion: Virtual endoscopy provided a more dynamic, direct, minimally invasive approach that was equal to or better than angiography for both the verification of the vascular stenosis and the evaluation of the arterial lumen. INTRODUCTION R ENAL ARTERY STENOSIS is a common pathological entity and is an established cause of hypertension and re- nal insufficiency. Atherosclerosis is the main cause in 90% of cases and usually involves the ostium and proximal third of the main renal artery and the perirenal aorta. 1,2 Detection of renal artery stenosis has routinely been per- formed with angiographic studies. Recently, however, the in- troduction of CT angiography and MR angiography has per- mitted a more accurate and dynamic evaluation of renal artery stenosis. 3–6 Virtual endoscopy (VE) represents a noninvasive tech- nique allowing amplification of the image in three-dimen- sional (3D) space, simulating the view of fiberoptic en- doscopy systems. In this respect, VE takes advantage of in- formation obtained in axial CT slices and further depicts the 3D relations of pathological regions. The study can provide views of the stenotic segment, as well of as the arterial lu- men beyond the stenosis. It has also been shown that VE pro- vides intraluminal as well as extraluminal information about a given tubular structure in all possible directions. Thus, VE enables the exploration of vascular structures that are unap- proachable with conventional procedures, irrespective of the size of the lumen. 7–11 In the present study, we applied VE as a diagnostic or fol- low-up study or both in patients with renal artery stenosis, es- pecially to define vascular patency. Thus, the aim of the pres- Departments of 1 Urology, 2 Radiology, and 3 Medical Physics, University of Patras, School of Medicine, Patras, Greece. 4 Department of Urology, Tufts University School of Medicine, Boston, Massachusetts. 540