Effect of Body Mass Index on Estimated Glomerular Filtration Rate Levels in Children With Congenital Solitary Kidney: A Cross-Sectional Multicenter Study

Rationale & objective: The objective of this study is to evaluate the effect of body mass index (BMI) on estimated glomerular filtration rate (eGFR) levels in children with congenital solitary kidney (CSK). Moreover, we evaluated if other factors could influence this relationship.

Study design: Multicenter cross-sectional study.

Setting & participants: University hospital pediatrics departments.

Subjects: Two hundred eighty-one patients with CSK.

Predictors: Weight, height, BMI-SDS (standard deviation score), duration of overweight/obesity, pubertal stage, systolic (SBP) and diastolic (DBP) blood pressure, eGFR, and renal ultrasound were obtained at the last follow-up visit. The population was classified on the basis of nutritional status and divided in tertiles for duration of overweight/obesity. We compared eGFR levels among these categories. A simple regression was used to correlate eGFR with BMI-SDS. To evaluate if other factors could influence the relationship between eGFR and BMI-SDS, a general linear model was performed, including gender, birth weight<2.5 kg, age, BMI-SDS, SBP-SDS, DBP-SDS, RL-SDS (renal length), and presence of kidney injury at last follow-up as covariates.

Results: The eGFR levels reduced gradually from underweight to obese patients (P = .047). The eGFR levels significantly increased across first and second tertiles of duration of overweight/obesity while they decreased across second and third tertiles of duration of overweight/obesity (P = .005). The eGFR and BMI-SDS at last follow-up were indirectly correlated (coefficient = -0.30, r² = 9.2%, P = .0004). A general linear model for eGFR variance (model R² = 26.37%; P = .02) confirmed an indirect and significant association of eGFR values with BMI-SDS as the only significant finding.

Conclusions: In patients with CSK, the higher the BMI-SDS and the duration of overweight/obesity, the lower the eGFR levels. Primary prevention strategies to counteract overweight/obesity are mandatory in CSK patients.