The relationship between body mass index and renal length in obese children

Background Obesity in the pediatric population is a severe public health problem and is associated with various comorbidities. Renal length is an important clinical parameter for the diagnosis and follow-up of renal diseases. The aim of this study was to determine the relationship between renal length (measured ultrasonographically) and body mass index (BMI) in obese children, and to develop nomograms for renal length according to BMI. Methods Renal ultrasound was performed in 368 children without renal disease. Each child’s age, gender, weight, height, and BMI (kg/m 2 ) were recorded. The children were divided into three groups according to BMI percentiles: obese group: BMI ≥ 95th percentile; overweight group: BMI 85th–94th percentile; normal weight group: BMI 5th–84th percentile. Results Weight, height, BMI, and right and left renal length differed significantly between the three groups ( p = 0.001). There were significant correlations between renal length with age, weight, height, and BMI. Measurement of renal length was independently associated with BMI, age, and height. BMI was used to create renal length nomograms for obese children, based on multiple regression analysis ( R 2 = 0.32 and p = 0.0001). Mean renal length was highest in the obese group (96.9 ± 13.4 mm) and lowest in the normal weight group (88.3 ± 12.9 mm). Conclusions Ultrasonographic measurement of the renal length according to BMI in children can be a useful method in evaluating these children. Smaller-than-normal kidneys can easily remain undiagnosed in obese and overweight children and this nomogram offers an additional method to evaluate the renal size in obese children.