Functional renal volume: quantitative analysis at gadolinium-enhanced MR angiography--feasibility study in healthy potential kidney donors

PURPOSE: To assess the feasibility of quantifying functional renal volume with gadolinium-enhanced magnetic resonance (MR) angiography. MATERIALS AND METHODS: Institutional review board approval was obtained, and all subjects gave informed consent. A contour-detection three-dimensional algorithm for determining renal volumes was developed. The method was validated in 18 cadaveric pig kidneys by measuring the water displacement caused by the kidneys. The kidney lengths and volumes in 19 consecutive potential kidney donors who underwent gadolinium-enhanced MR angiography of the renal arteries also were determined. Differences in volume measurements between men and women and between left and right kidneys were analyzed by using the Student t test. The volume of perfused renal cortex was calculated by extracting voxels on the basis of the cortex signal intensity threshold. The relevance of renal function parameters--namely, creatinine clearance rates--in the donor candidates was assessed by using a linear regression model. Intra- and interobserver variabilities of the measurements were determined by using the Bland-Altman method. RESULTS: Volume measurements of the cadaveric pig kidneys obtained by using MR angiography and the water displacement method were strongly correlated (r = 0.99). The mean total renal volume in the donor candidates was 196 mL (range, 136-295 mL). No significant differences in total renal volume between the men and women or between the left and right kidneys were found. The correlation between calculated renal cortex volumes (mean, 67 mL; range, 40-105 mL) and creatinine clearance rates was good (r = 0.69). Inter- and intraobserver variabilities were lower than 7%. CONCLUSION: Quantification of functional renal volume with three-dimensional gadolinium-enhanced MR angiography seems feasible with use of the described semiautomatic method.