Faculty Bibliography

OBJECTIVES: To evaluate changes in single-kidney glomerular filtration rate (SK-GFR) using low-dose dynamic contrast-enhanced magnetic resonance (MR) renography (MRR) in patients undergoing partial nephrectomy for renal masses. MATERIALS AND METHODS: In this Health Information Patient Protection Act-compliant prospective study, 18 patients with renal masses underwent preoperative MR imaging at 1.5 T for renal mass evaluation and low-dose gadolinium-enhanced MRR. Magnetic resonance renography was repeated approximately 48 to 72 hours and 6 months after partial nephrectomy. Single-kidney glomerular filtration rate was calculated from the MRR images, and the right and left kidney values were summed for total MR-GFR. Postoperative changes in SK-GFR and MR-GFR were compared with changes in estimated glomerular filtration rate calculated using modification of diet in renal disease formula, renal lesion characteristics, ischemia type (warm vs cold), and ischemia time. RESULTS: A decrease in the operated kidney SK-GFR was seen in 15 of the 18 patients, with a mean (SD) loss of 31% (23%), whereas estimated glomerular filtration rate decreased in 13 of the 18 patients with mean (SD) decrease of 19% (14%). Decrease in SK-GFR was greatest in the patients with warm ischemia time greater than 40 minutes and least in the patients with cold ischemia. In the immediate postoperative period, 6 of 7 patients (86%) with preoperative MR-GFR less than 60 mL/min per 1.73 m failed to demonstrate compensatory increase in SK-GFR in the nonoperated kidney, whereas 5 of 11 patients with baseline MR-GFR more than 60 mL/min per 1.73 m showed compensatory increase in nonoperated kidney SK-GFR. CONCLUSIONS: Magnetic resonance renography can demonstrate functional loss in the operated kidney and compensatory increase in the function of the contralateral kidney, thus enabling evaluation of various surgical techniques on kidney function.

OBJECTIVE. The purpose of this review is to describe the role of functional renal MRI, or MR renography, in the care of patients with renal masses undergoing partial nephrectomy. CONCLUSION. MR renography can be used to monitor renal functional outcome for patients undergoing partial nephrectomy and may help guide patient selection in this population with elevated risk of chronic kidney disease.

Ectopic ureters are rare congenital mesonephric duct malformations with a higher prevalence in women than men. In women, ectopic ureters are often associated with a duplicated collecting system, whereas in men, ectopic ureters usually drain a single system and are associated with renal dysplasia and obstruction. Presentation and diagnosis generally occurs in the pediatric age group. Herein, we present an unusual case of delayed diagnosis of ectopic insertion of the upper pole ureter in a completely duplicated left kidney causing massive hydroureteronephrosis in an adult man.

Background: Small renal masses (SRM) are comprised of a heterogeneous group of tumors with some having malignant potential. Although surgery is the standard treatment for SRMs, emerging data suggests that surgery in the elderly or morbidly ill patients may be unnecessary and may adversely impact non-oncologic outcomes. We analyzed a population-based cohort of patients to identify predictors of surveillance and assess the impact of surveillance on overall survival, kidney cancer-specific survival and cardiovascular (CV) events, compared with surgery. Methods: From surveillance, epidemiology, and end results (SEER) cancer registry data linked with Medicare claims, we performed a retrospective cohort study of patients 66 years of age or older who received surgery or surveillance for SRM (< 4 cm) diagnosed between 2000 to 2007. Propensity score methods were used to control for potential confounders in multivariable analysis. Results: Of 8,317 patients, 5,706 (70%) underwent surgery and 2,611 (31%) underwent surveillance. The use of surveillance increased from 25% in 2000 to 37% in 2007 (p < 0.001). During a median follow-up of 58 months, 2,053 (25%) patients had at least one CV event and 2,078 (25%) patients died, including 277 (3%) who died of kidney cancer. Compared with surgery, surveillance was associated with a significantly lower risk of death from any cause (hazard ratio [HR], 0.84; CI, 0.75-0.94) and of suffering a CV event (HR, 0.79; CI 0.70-0.89), controlling for patient and disease characteristics. Kidney cancer-specific survival did not differ by treatment approach (HR, 0.89; CI, 0.66-1.21). Conclusions: There is increasing utilization of surveillance as an initial treatment strategy for patients with SRMs. For older patients with SRM, surveillance does not appear to adversely affect kidney cancer-specific survival, while surgery may be associated with CV complications and an increased risk of death from any cause. Surveillance should be considered an option for patients with SRM who ar!

PURPOSE: The aim of this study was to use intravoxel incoherent motion diffusion-weighted imaging to discriminate subtypes of renal neoplasms and to assess agreement between intravoxel incoherent motion (perfusion fraction, fp) and dynamic contrast-enhanced magnetic resonance imaging (MRI) metrics of tumor vascularity. SUBJECTS AND METHODS: In this Health Insurance Portability and Accountability Act-compliant, institutional review board-approved prospective study, 26 patients were imaged at 1.5-T MRI using dynamic contrast-enhanced MRI with high temporal resolution and diffusion-weighted imaging using 8 b values (range, 0-800 s/mm). Perfusion fraction (fp), tissue diffusivity (Dt), and pseudodiffusivity (Dp) were calculated using biexponential fitting of the diffusion data. Apparent diffusion coefficient (ADC) was calculated with monoexponential fit using 3 b values of 0, 400, and 800 s/mm. Dynamic contrast-enhanced data were processed with a semiquantitative method to generate model-free parameter cumulative initial area under the curve of gadolinium concentration at 60 seconds (CIAUC60). Perfusion fraction, Dt, Dp, ADC, and CIAUC60 were compared between different subtypes of renal lesions. Perfusion fraction was correlated with CIAUC60. RESULTS: We examined 14 clear cell, 4 papillary, 5 chromophobe, and 3 cystic renal cell carcinomas (RCCs). Although fp had higher accuracy (area under the curve, 0.74) for a diagnosis of clear cell RCC compared with Dt or ADC, the combination of fp and Dt had the highest accuracy (area under the curve, 0.78). The combination of fp and Dt diagnosed papillary RCC and cystic RCC with 100% accuracy, and clear cell RCC and chromophobe RCC, with 86.5% accuracy. There was significant strong correlation between fp and CIAUC60 (r = 0.82; P < 0.001). CONCLUSION: Intravoxel incoherent motion parameters fp and Dt can discriminate renal tumor subtypes. Perfusion fraction demonstrates good correlation with CIAUC60 and can assess degree of tumor vascularity without the use of exogenous contrast agent.