We used EPI-Data Version 3.1 for data entry. All analyses were performed using R
v.4.2.1 (RStudio 2022.07.2+576). Descriptive statistics for continuous variables
were described using central tendency (mean) and dispersion (standard
deviation). A 1-way analysis of variance (ANOVA) was conducted to compare the
means of anthropometric measurements among children of each age group. A Pearson
product-moment correlation was run to determine the relationship between age,
weight, height, waist circumference, xipho-pubic distance, BSA, abdominal
volume, and sonographic measurements of the right and left kidneys. Height and
BSA-related kidney length and volume curves and tables were generated after
lambda-mu-sigma (LMS) quantile regression with a Box-Cox Transformation to
Normality was fitted using the vector generalized additive model (VGAM) and
generalized additive model for location, scale and shape (GAMLSS) method (R,
VGAM, and GAMLSS package).