PP066 - URINARY NET ACID EXCRETION OUTSIDE THE NORMAL RANGE IS ASSOCIATED WITH FASTER EGFR DECLINE IN PATIENTS WITH SHORT BOWEL SYNDROME

PP066

URINARY NET ACID EXCRETION OUTSIDE THE NORMAL RANGE IS ASSOCIATED WITH FASTER EGFR DECLINE IN PATIENTS WITH SHORT BOWEL SYNDROME

R. H. Foerster^1,*, G. Lamprecht¹, N. Sattelberg¹, J. Leipziger², M. V. Sørensen², P. Berg²

¹Division of Gastroenterology, Hepatology and Nutritional Medicine, Rostock University Medical Center, Rostock, Germany, ²Department of Biomedicine, Health, Aarhus University, Aarhus, Denmark

Rationale: Patients with short bowel syndrome (SBS) have an increased risk of developing chronic kidney disease. We previously demonstrated that a large proportion of patients with SB exhibit markedly abnormal 24-hour net acid excretion (NAE), with values ranging from -156 to 232 mmol/day. We hypothesized that both very low and very high NAE may impose additional renal stress and associate with accelerated decline in kidney function.

Methods: NAE was calculated as the 24-hour urinary excretion of ammonium plus titratable acids minus bicarbonate. Estimated glomerular filtration rate (eGFR) was derived from plasma creatinine. Associations between NAE and eGFR decline were assessed using mixed-effects models for repeated measurements. Analyses were performed with and without adjustment for sex, age, SBS anatomy (with or without colon in continuity), and systemic acid–base and volume status (plasma renin).

Results: Among 147 patients, the overall decline in eGFR was -1 mL/min/1.73 m² per year (95% CI: -1.8 to -0.3, p < 0.01). There was no difference in eGFR decline between patients with and without a colon in continuity. NAE measurements and at least one follow-up eGFR were available for 66 patients (50 on home parenteral support). Over a median follow-up of 2.5 years (IQR: 1.2-3.1), baseline NAE was significantly associated with eGFR decline (unadjusted and adjusted p < 0.01). The relationship was bell-shaped, with the smallest annual decline observed at an NAE of approximately 70 mmol/day. NAE values above 100 or below 30 mmol/day were associated with a 3.3 mL/min/1.73 m² (95% CI: -6.3 to -0.3, p < 0.05) per year faster decline in eGFR.

Conclusion: Both low and high urinary net acid excretion are associated with accelerated eGFR decline in patients with SBS. Future studies should determine whether interventions that normalize NAE can mitigate kidney function loss in this population.

Disclosure of Interest: R. Foerster Other: Listed as inventor on a patent application filed by Aarhus University describing urine net acid excretion as a biomarker to guide parental base supplementation, G. Lamprecht Other: Listed as inventor on a patent application filed by Aarhus University describing urine net acid excretion as a biomarker to guide parental base supplementation, N. Sattelberg: None declared, J. Leipziger Other: Listed as inventor on a patent application filed by Aarhus University describing urine net acid excretion as a biomarker to guide parental base supplementation, M. Sørensen Other: Listed as inventor on a patent application filed by Aarhus University describing urine net acid excretion as a biomarker to guide parental base supplementation, P. Berg Other: Listed as inventor on a patent application filed by Aarhus University describing urine net acid excretion as a biomarker to guide parental base supplementation