Differential renal function estimation using computerized tomography based renal parenchymal volume measurement

Nuclear renal scan is currently the gold standard imaging study to determine differential renal function. We propose helical computerized tomography as a more efficient way to gain renal function information. Renal parenchymal volume is measured and percent total renal volume is used as a surrogate marker for differential renal function.

Computerized tomography and diuretic enhanced nuclear renal scan were performed in 33 patients with chronic obstruction. Computerized tomography was contrast enhanced in 23 cases and nonenhanced in 10. Diagnoses included ureteropelvic junction obstruction, ureteral stricture and extrinsic compression. Using semiautomated boundary delineation with manual editing method the parenchymal volume of each kidney was measured and percent renal volume was calculated. Percent renal volume was compared with percent renal function, as determined by nuclear renal scan. Correlations between the 2 measures were evaluated using the Spearman or Pearson coefficient.

Strong correlations were observed between percent renal function and percent renal volume in all cases (r = 0.90, p <0.001), including the enhanced (r = 0.87, p <0.001) and nonenhanced (r = 0.95, p <0.001) groups. Moderately strong correlations were noted in the less than 40% (r = 0.76, p <0.001) and less than 30% (r = 0.64, p = 0.015) renal function subgroups.

Differential renal volume measured from computerized tomography strongly correlates with differential renal function on nuclear renal scan for normal and chronically obstructed kidneys. Computerized tomography may serve as a single radiological diagnostic study for anatomical and functional assessment in patients in whom a poorly functioning kidney is suspected.