92 - Characterization of Nephrolithiasis and Stone Risk Profile in Children and Young Adults with Inflammatory Bowel Disease

Poster Number: 92

Sonya R. Kowalczyk, Childrens Hospital of Philadelphia, Philadelphia, PA, United States; Melissa S. Zhou, Childrens Hospital of Philadelphia, Philadelphia, PA, United States; Elana Mitchel, University of Pennsylvania /Childrens Hospital of Philadelphia, Philadelphia, PA, United States; Lawrence Copelovitch, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States; LIndsey Albenberg, Children's Hospital of Philadelphia, Philadelphia, PA, United States; Michelle Denburg, Childrens Hospital of Philadelphia, Philadelphia, PA, United States; Rebecca R. Scobell, Childrens Hospital of Philadelphia, Philadelphia, PA, United States

Background: Nephrolithiasis has been described as an extraintestinal manifestation of inflammatory bowel disease (IBD), mostly in adults. Several pathogenic mechanisms have been proposed including alterations in intestinal absorption and chronic dehydration. Studies characterizing nephrolithiasis in pediatric IBD are limited.

Objective: To determine the prevalence of nephrolithiasis within a large pediatric population with IBD and describe kidney stone composition and urine chemistries.

Design/Methods: This was a retrospective cohort study of patients diagnosed with IBD between January 2010-January 2021 within a single large IBD center. Patients were identified using a validated algorithm of ≥2 gastroenterology encounters (≥1 outpatient office visit) with an ICD9/10 code for Crohn’s disease (CD, 555.x, K50.x) or ulcerative colitis (UC, 556.x, K51.x). Chart reviews were performed for patients with ≥1 encounter with nephrology or urology.

Results: Of 2359 patients with IBD, 124 (5.3%) had ≥1 encounter with nephrology and 168 (7.1%) had ≥1 encounter with urology. Of these patients, 38 were diagnosed with nephrolithiasis or nephrocalcinosis, representing 1.6% of the entire cohort. 52.6% of patients with nephrolithiasis were female, 82% were white (10.5% Black or African American, 7.5% other), and median age at start of follow-up was 12.7 years (IQR 9.7-15.2). 27 (71.0%) had a diagnosis of CD, 9 (23.7%) UC, and 2 (5.3%) indeterminate colitis (comparable to the subtype distribution of the full cohort). 10 patients required procedural intervention for their stones (range 1-5 procedures). 17 patients had stone analyses; the most common compositions were calcium oxalate (n=12), calcium phosphate (n=6), and ammonium acid urate (n=4). 23 patients completed ≥1 24-hour urine risk profile with common findings being hypocitraturia (n=16), low urine volume (n=12), and hyperoxaluria (n=7). 7 patients had increased super-saturation of calcium oxalate despite normal concentrations of each, driven by low urine volume and/or hypocitraturia. 9 patients (24%) met criteria for chronic kidney disease stage 2-5 or had ≥1 episode of acute kidney injury during follow-up.Conclusion(s): Our study found a higher percentage of patients with identified nephrolithiasis (1.6%) in the IBD population compared to that predicted in the overall US pediatric population (36 to 145 per 100,000), with no IBD subtype at increased risk compared to others. Urine chemistries demonstrated hypocitraturia and hyperoxaluria as prominent factors, which may be reflective of chronic diarrhea and malabsorption.