Length and Volume of Morphologically Normal Kidneys in Korean Children: Ultrasound Measurement and Estimation Using Body Size

Objective: To evaluate the relationship between anthropometric measurements and renal length and volume measured with ultrasound in Korean children who have morphologically normal kidneys, and to create simple equations to estimate the renal sizes using the anthropometric measurements. Materials and Methods: We examined 794 Korean children under 18 years of age including a total of 394 boys and 400 girls without renal problems. The maximum renal length (L) (cm), orthogonal anterior-posterior diameter (D) (cm) and width (W) (cm) of each kidney were measured on ultrasound. Kidney volume was calculated as 0.523 ${\times}$ L ${\times}$ D ${\times}$ W ( $cm^3$ ). Anthropometric indices including height (cm), weight (kg) and body mass index ($m^2/kg$) were collected through a medical record review. We used linear regression analysis to create simple equations to estimate the renal length and the volume with those anthropometric indices that were mostly correlated with the US-measured renal sizes. Results: Renal length showed the strongest significant correlation with patient height (R2, 0.874 and 0.875 for the right and left kidneys, respectively, p < 0.001). Renal volume showed the strongest significant correlation with patient weight (R2, 0.842 and 0.854 for the right and left kidneys, respectively, p < 0.001). The following equations were developed to describe these relationships with an estimated 95% range of renal length and volume ($R^2$, 0.826-0.884, p < 0.001): renal length = 2.383 + 0.045 ${\times}$ Height (${\pm}$ 1.135) and = 2.374 + 0.047 ${\times}$ Height (${\pm}$ 1.173) for the right and left kidneys, respectively; and renal volume = 7.941 + 1.246 ${\times}$ Weight (${\pm}$ 15.920) and = 7.303 + 1.532 ${\times}$ Weight (${\pm}$ 18.704) for the right and left kidneys, respectively. Conclusion: Scatter plots between height and renal length and between weight and renal volume have been established from Korean children and simple equations between them have been developed for use in clinical practice.