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Abstract: PO2252

Relationship Between 24-Hour Urinary Oxalate and Incident CKD Among Patients with and Without Underlying Gastrointestinal Disease

Session Information

Category: CKD (Non-Dialysis)

  • 2101 CKD (Non-Dialysis): Epidemiology, Risk Factors, and Prevention

Authors

  • Puurunen, Marja, Synlogic, Cambridge, Massachusetts, United States
  • Curhan, Gary C., OM1, Cambridge, Massachusetts, United States
  • Behling, Michael, OM1, Cambridge, Massachusetts, United States
  • Kurtz, Caroline B., Synlogic, Cambridge, Massachusetts, United States
  • Macdougall, James, Synlogic, Cambridge, Massachusetts, United States
  • Brennan, Aoife M., Synlogic, Cambridge, Massachusetts, United States
  • Riese, Richard, Synlogic, Cambridge, Massachusetts, United States
Background

Hyperoxaluria may result from intake of high oxalate foods or enhanced intestinal absorption of dietary oxalate caused by gastrointestinal (GI) disorders with underlying malabsorption, including Crohn’s disease, short bowel syndrome, gastric bypass surgery, and chronic pancreatitis. Hyperoxaluria has been associated with negative outcomes, including kidney stones and chronic kidney disease (CKD), but larger studies are needed.

Methods

This is a longitudinal retrospective observational cohort study of patients in the US who have completed at least one 24-hr urine collection analyzed by a central laboratory during the study period of January 2013 through December 2020. Outcome and covariate data were drawn from a multi-source data cloud containing deterministically linked, de-identified, individual-level healthcare claims and electronic medical records (EMR) data. Malabsorption was defined by the presence of a relevant ICD 9/10 or CPT code. The association between categories of urine oxalate (UOx) and incident CKD was modeled using logistic regression.

Results

762,537 individuals age ≥ 18y with at least one 24-hr urine collection were identified. At least 6 months of baseline and 6 months of follow-up data (median follow-up time: 36.7 months; IQR: 20.4, 56.0) were available for 447,958. Of these, N=12,522 (2.8%) had an underlying malabsorptive condition preceding the index urine test. 426,896 patients had no evidence of CKD at baseline and were eligible for analysis of incident CKD. After adjusting for baseline urine calcium, urine citrate, age, sex, race, BMI, tobacco use, hypertension, diabetes, malabsorption, and CVD, a significant association between baseline UOx and the development of incident CKD was observed. Compared with patients with UOx <20 mg/d, the odds of developing incident CKD increased for 20-29 mg/d (OR: 1.22, 95% CI: 1.15, 1.30) through 80+ mg/d (OR: 1.67, 95% CI: 1.51, 1.86) and was statistically significant for each UOx category.

Conclusion

In this large population of patients with hyperoxaluria, the risk of incident CKD increased with increasing 24-hr urine oxalate excretion. Future studies should examine whether reducing urine oxalate diminishes the risk of developing CKD.

Funding

  • Commercial Support