BMI Differences in Pediatric Patients with and without Nephrolithiasis by Pubertal Status
Arthi Hannallah, MD1, Zoë G. Baker, PhD, MPH1, Shirley Saker, BSc2, Nadine Khouzam, MD1, S. Scott Sparks, MD1.
1Children's Hospital Los Angeles, Los Angeles, CA, USA, 2University of Southern California, Los Angeles, CA, USA.
BACKGROUND: The link between obesity and nephrolithiasis is well-established in adults, but not in children. We hypothesize that upon puberty, pediatric patients with nephrolithiasis will have higher mean body mass indexes (BMI) than patients without nephrolithiasis.
METHODS: This was a retrospective, single center review of healthy pediatric patients with nephrolithiasis from 2007 to 2021. Patients with comorbidities, genetic conditions causing nephrolithiasis, or age less than 2 years were excluded. Puberty was defined as occurring between the ages of 9 and 14 years, with younger than 9 years being prepubertal and older than 14 years being postpubertal. BMI classifications were determined by the Center the Centers for Disease Control (CDC) guidelines: underweight was defined as less than 5th BMI percentile for age, overweight was 85th to 95th percentile, and obesity as 95th percentile and above. Sex, height, and weight at first stone visit were recorded. An age- and sex-matched control population was determined using a de-identified national database of pediatric patients (TriNetX) by including healthy patients with no comorbidities or nephrolithiasis history. Associations between pubertal status and BMI by sex, and associations between BMI percentile weight status and stone composition were assessed with one-way analysis of variance (ANOVA) and Pearson X2 tests.
RESULTS: Among 221 healthy patients with nephrolithiasis, 47 were prepubertal, 72 were pubertal, and 102 were postpubertal. In the stone cohort, rates of overweight and obese patients were highest in postpubertal and pubertal patients compared to controls (Figure 1). Pubertal and postpubertal patients with nephrolithiasis had significantly higher BMIs than control patients, with some gender variations (Table 1). Prepubertal males with nephrolithiasis had significantly higher mean BMIs than control (p=0.03). Among prepubertal females, mean BMIs were similar between the stone cohort (16.0 ± 2.7) and the control cohort (16.6 ± 3.1, p=0.38). There was a statistically significant increase in BMI among pubertal and postpubertal patients with nephrolithiasis compared to controls (p=0.002 and p=0.003, respectively, Table 1). Additionally, prepubertal and pubertal male stone patients were significantly more likely to be overweight or obese than prepubertal and pubertal males with no history of stones (p=0.05, p=0.03; Table 1). Healthy weight patients were significantly more likely to form predominantly carbonate apatite stones (13/57; 22.8%), compared to overweight/obese patients (2/39; 5.1%; p=0.03).
CONCLUSIONS: Healthy pediatric patients with nephrolithiasis have significantly higher BMIs during pubertal and postpubertal ages, compared to healthy patients without nephrolithiasis. Overweight and obese children form more calcium oxalate stones, as do obese adults. Promoting obesity prevention measures in adolescent pediatric patients with nephrolithiasis should be a key component of management. 
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