Measurement of skin-to-kidney distance in children: implications for quantitative renography

Variation in skin-to-kidney center distance has been shown to have a significant influence on quantification of renal function with the gamma camera. Several techniques to compensate for this variability have been proposed in adults, yet it has been suggested that depth correction is not necessary for quantitative renography in children. Skin-to-kidney center distances were measured from computed tomograms in 53 supine pediatric patients. Nearly 40% of the kidneys examined varied more than 1 cm from the average renal depth, and 8% deviated more than 2 cm. Right kidney depth differed from left kidney depth by more than 1 cm in less than 10% of the patients. Measurements were in agreement with regression equations based on lateral scintigraphy in children, but were consistently underestimated by nomograms developed for skin-to-kidney center distance in adults. Failure to recognize interindividual variability in skin-to-kidney center distance can introduce significant errors in quantitative pediatric renography.