Factors Affecting the Measurement of Renal Length

Abstract

The variation in kidney length between the 1-min radiograph (centered over the kidney) and the 5-min study (centered over the mid-abdomen) was evaluated on 100 random [human] excretory urograms. When both kidneys were measurable, the change in kidney size was discordant in 40%. Most such changes are due to changes in geometery, differences in centering, or changes in the angle of the kidney with respiration. These alterations are of much greater magnitude than the reported swelling of the kidney due to contrast medium. Since there is practically no relation between the time of injection and changes in renal image size, it makes no difference whether the 1-min or 5-min radiograph is selected for measurement.