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Abstract: PO1162

Higher Risk of Incident Kidney Stones in Patients with Metabolic Acidosis and CKD

Session Information

Category: Fluid, Electrolyte, and Acid-Base Disorders

  • 902 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

  • Reaven, Nancy L., Strategic Health Resources, La Canada, California, United States
  • Funk, Susan E., Strategic Health Resources, La Canada, California, United States
  • Mathur, Vandana S., MathurConsulting, Woodside, California, United States
  • Lai, Julie C., Strategic Health Resources, La Canada, California, United States
  • Tangri, Navdeep, Division of Nephrology, University of Manitoba, Winnipeg, Manitoba, Canada
Background

Epidemiological studies have shown an association between kidney stones and risk for CKD and its progression. Some types of stones are less likely to form at higher urine pH. Metabolic acidosis is a risk factor for CKD progression, but the association of serum bicarbonate with risk of incident kidney stones is not well understood.

Methods

Optum’s de-identified Integrated Claims-Clinical dataset of US patients (2007-2019) was queried to identify patients with non-dialysis CKD stages 3-5 with 2 consecutive serum bicarbonate values of 12 to <22 mEq/L (metabolic acidosis) or 22 to <30 mEq/L (normal serum bicarbonate) with data ≥3 years pre-index. The first qualifying serum bicarbonate test established the index date. Primary exposure variables were baseline serum bicarbonate and change in serum bicarbonate over time. Adjusted time-dependent Cox Proportional Hazards models were performed to evaluate time to first occurrence of kidney stones (by ICD-9 or ICD-10 diagnosis codes) during an average 3.6 year follow-up period. Other covariates included age, sex, race-ethnicity, education and income status, history of kidney stones, pre-index comorbidities associated with kidney stones, bariatric surgery, obesity, smoking history, baseline eGFR.

Results

142,904 patients qualified for the study cohort. Patients with metabolic acidosis at index experienced kidney stones at greater frequency than those with normal serum bicarbonate at index (12% vs 9%, p<0.0001). Other significant factors associated with incident kidney stones included male sex, history of kidney stones, hyperoxaluria, gout and osteoporosis. Both higher serum bicarbonate at baseline (HR 0.956, 95% CI: 0.948-0.964) and higher serum bicarbonate over time (HR 0.968, 95% CI: 0.961-0.974) were associated with reduced risk of kidney stone development. The observed associations were unchanged in analyses examining death as a competing risk.

Conclusion

In patients with CKD, metabolic acidosis (vs. normal serum bicarbonate) was associated with a higher incidence of kidney stones and shorter time to incident stone formation. Future investigations should evaluate these associations by stone type.

Funding

  • Commercial Support