Purpose: The purposes of this study were to establish reference values for renal size determined from 99mTc-MAG3 renal scintigraphy and to derive regression equations to predict normal limits.
Methods: The study population consisted of 106 subjects evaluated for kidney donation who underwent 99mTc-MAG3 renal scintigraphy. Renal length, width, and area were determined from the pixel length and area of whole-kidney regions of interest and correlated with patient sex, height, weight, body mass index, and body surface area (BSA). Reference values were obtained based on estimation of the lower and upper percentiles via quantile regression.
Results: The mean (SD) left and right kidney lengths was 12.2 (1.0) and 12.1 (1.0) in male and 11.9 (0.9) and 11.8 (0.9) in female patients, respectively. Sex was not a significant factor in the quantile regression models. Regression equations defining the lower and upper limits of renal length (cm) and area (cm) are as follows: left kidney length (5th percentile), 8.2+1.3×BSA; left kidney length (95th percentile), 9.1+2.3×BSA; right kidney length (5th percentile), 8.8+1.0×BSA; right kidney length (95th percentile), 11.1+1.4×BSA; left kidney area (5th percentile), 32.5+9.6×BSA; left kidney area (95th percentile), 12.6+31.7×BSA; right kidney area (5th percentile), 16.1+18.5×BSA; right kidney area (95th percentile), 32.6+22.2×BSA.
Conclusions: Regression equations have been developed, which define the upper and lower limits of renal size from 99mTc-MAG3 images and may assist in the detection of unsuspected bilateral increases or decreases in renal size.