Technetium-99m-MAG3 Renal Studies: Normal Range and Reproducibility of Physiologic Parameters as a Function of Age and Sex

The normal range and reproducibility of common physiologic parameters for 99mTc-MAG3 renal studies were quantitated in normal subjects. Six females and six males in each of three age groups, 21-40, 41-60 and 61-80 yr, were each studied twice. Renal clearance (camera based method), percent function in each kidney, time of peak renal parenchymal activity and half time of parenchymal activity following the peak were evaluated. The peak and half times were determined with regions of interest (ROIs) over the entire kidney and over the cortex only. There were no significant differences between sexes for any parameter. The only significant difference among age groups was a decrease in renal clearance, normalized for body surface area, with increasing age (p < 0.01). The percent function in each kidney, time of peak parenchymal activity and half time following the peak were symmetrical and did not vary with age or sex. The peak times were always less with cortical ROIs (p < 0.05). In serial studies in the same subject the percent s.d. for clearance and percent function in each kidney was less than half of the percent s.d. in single studies, suggesting that at least one half of the error is due to intersubject variation (p < 0.05). We conclude that: (1) renal clearance decreases with age in normal subjects, (2) cortical ROIs are superior to renal ROIs in measuring peak parenchymal activity, and (3) variation in clearance and percent function per kidney in serial studies is approximately one half the variation in single studies.