Measurement of renal parenchymal volume using computed tomography

In hydronephrosis, total renal volume is not correlated with renal parenchymal volume. We have used computed tomography (CT) to determine renal parenchymal volume in 17 control patients and 36 patients with unilateral hydronephrosis. An additional 17 patients were studied before and 2 weeks after renal surgery. Renal parenchymal volume was determined by summing up the parenchymal area in each scan, taken at 10 mm intervals. Renal parenchymal volume measured by CT correlated well with renal area on excretory urography in normal kidneys. Renal parenchymal volume in hydronephrosis, however, was totally unrelated to renal area on excretory urography because of the grossly dilated calyceal system. Reproducibility of this study was ascertained in 17 patients using the contralateral nonoperated kidneys before and after the surgery (r = 0.939; p less than 0.01).