Renal cortical volume measured by MRI: a feasibility study
Purpose We present a novel MRI technique to measure the renal cortical volume (Vc). This objective is motivated by the fact that renal function is primarily driven by the glomerular function taking place in the renal cortical segment, and thus, shrinkage or growth of renal cortex could become a determinant factor for the kidney function. Material and methods We included 22 adult pigs: 13 healthy and 9 with relieved unilateral ureteral obstruction (UUO). MRI volumetry of both kidneys was performed using two different strategies: one without MR contrast-agent, and one with MR contrast-agent. The acquired images were analysed using both semiautomatic and manual segmentation of the renal cortex, and Vc was calculated. Nephrectomy was subsequently performed and reference values of Vc were estimated by stereology. Results Vc in healthy pigs was estimated quite precisely with both MRI methods as compared with reference values. In UUO kidneys, the non-contrast MRI method gave Vc values comparable to those found by stereological means, whereas contrast-agent MRI method overestimated Vc slightly. Second, we found that semiautomatic and manual segmentation resulted in almost similar Vc values. Reproducibility of estimated cortical volumes offered both intra- and interindividual differences below 5%. Conclusions We found that MRI volumetry of renal cortex can be performed with high precision and high reproducibility. This study presents a novel non-contrast-agent MRI method that allows accurate estimation of Vc, both in healthy and diseased animals. We believe that it could become a supplementary tool to daily invasive measures in kidneys.