Objective To evaluate prospectively the accuracy of computer-aided three-dimensional (3D) volumerendered computed tomography (CT) in determining the appropriate anatomical limits (tumour size, tumour location, multifocality and vascular supply) and as a potential tool in the preoperative simulation of nephron-sparing surgery (NSS) in patients with small-volume renal cell carcinoma (RCC). Patients and methods The study included 36 patients who underwent transperitoneal radical nephrectomy for RCC of <4 cm diameter. Helical CT was undertaken before surgery and the extent of the tumour, the course of major renal arteries and veins, and the relationship of the tumour to the collecting system were shown by 3D volume-rendered CT. The CT ®ndings were compared with the pathological results of all kidney specimens, obtained using 3-mm stepsections. Results Before nephrectomy, 39 renal tumours were identi®ed in the 36 patients; three renal lesions of <4 mm were not detected. All main venous branches and 42 of 43 arteries were identi®ed by 3D volumerendered CT. Knowing these features, a partial nephrectomy was simulated; a surgical lesion to the pelvicalyceal or vascular system which would have been produced by the simulated surgery was displayed in colour on the simulated surface of the section. Conclusion Computer simulation provided an excellent 3D reconstruction of all kidneys, including the tumour, vasculature and renal hilum, allowing a signi®cantly better preoperative evaluation of the renal mass. Visualizing possible resection margins and predicting the operative risks seem to be major advantages of this new method, especially when preparing for complex surgery. Reconstructed 3D CT appears to be a useful tool for de®ning the indications for and limitations of NSS.

Background: The indication for elective nephron-sparing surgery (NSS) in renal cell carcinoma (RCC) is under discussion in the urological literature. The main problem of NSS is the multifocality of RCC. The presented study was performed to asses the accuracy of pre- and intraoperative ultrasound (US), and computerized tomography (CT) in determination of tumor size and detection of multifocal lesions. Materials and Methods: Tumor size was measured by preoperative US and CT and compared with the tumor diameters in gross sections of the neoplastic kidneys. Multifocality was determined by 3-mm step sectioning of the nephrectomy specimen, and the results were correlated with preoperative US and CT on the one hand, and the ex situ sonography of the nephrectomized kidney on the other hand. Results: US and CT show similar results in the determination of the tumor size. In only 22.9%, preoperative US and CT were able to detect multifocal tumors. Ex situ sonography had a sensitivity of 40.0% and a specificity of 87.2% in this regard. Conclusions: In preparation for nephron-sparing surgery of renal cell carcinoma, neither preoperative routine imaging, nor intraoperative ultrasound can safely predict multifocal lesions of renal cell carcinoma.

Ureteral obstruction is an infrequent complication after renal transplantation that may cause rapid loss of transplant function. We tested static fluid MR urography for determining the cause of graft hydronephrosis. Magnetic resonance urography was performed in nine transplants with dilated collecting systems on ultrasound. A heavily T2-weighted 3D turbo spin-echo sequence on a 1.5-T scanner was used and maximum intensity projections were obtained. The patients also underwent excretory urography (n = 1), renal scintigraphy (n = 1), antegrade pyelography (n = 3), voiding cystourethrography (n = 4), and non-enhanced CT (n = 2). Six patients had pathologic conditions including ureteral stricture, compression by lymphoceles, implantation stenosis, vesicoureteral reflux, and late-occurring transitional cell carcinoma at the implantation site. Static MRU was able to diagnose or exclude a dilation of the graft collecting system. It visualized the course of the ureters and localized the obstruction site in four of five obstructed transplants. In one case the ureter was obscured by lymphoceles, which were demonstrated by hydrographic MRU as well. The definite cause for obstruction was provided in only 2 of 5 cases. Dilation due to vesicoureteral reflux could not be differentiated. The current multimodality approach to renal transplant imaging already provides comprehensive assessment of graft hydronephrosis. Static MRU may be useful in some cases since complications associated with intravenous iodinated contrast or antegrade pyelography can be avoided. Its main drawback, the lack of functional information, may be overcome by combining it with contrast-enhanced MRU.

Renal cell carcinoma in a horseshoe kidney is an unusual entity. To our knowledge, only 123 cases have been published to date. We report the first bilateral case of two clear-cell carcinomas in an asymmetrically fused kidney. Optimum preservation of renal function after radical tumor removal requires accurate preoperative imaging. Since the vascular supply in fusion anomalies is extremely variable, angiography is mandatory. Magnetic resonance imaging was most suitable to predict the tumor extent and localization, because it simultaneously gave the most comprehensive anatomical overview of the malformation.

We describe a case of aortic coarctation at the level of the infrarenal abdominal aorta which is encountered in less than six individuals in one million. In contrast to aortic narrowing above or including the renal arteries, this seems to be a relatively benign anomaly without systemic hypertension or impaired renal function. For the first time in this type of anomaly, contrast-enhanced MR angiography (ce-MRA) on a multi-receiver channel MR system, with an 8-channel phased array coil and parallel imaging was used. Ce-MRA displayed a tortuous, narrowed aortic segment that was found to be associated with mesenteric artery stenosis and compression of the orthotopic left renal vein, also known as the nutcracker phenomenon. All major aortic branches could be depicted using 3D surface-shaded displays and subvolume maximum intensity projections (MIPs). Collateral vessels of the abdominal wall were identified using whole-volume MIPs. Since the majority of aortic malformations are diagnosed at a younger age, and many suffer from renal insufficiency, we conclude that ce-MRA will eventually place conventional DSA as the modality of choice in malformations of the abdominal aorta.