Association of Renal Function Deterioration with Baseline Uricosuria.

Introduction Previous studies have found a relative risk of 1.6-2 for renal function deterioration with serum uric acid (UA) level increment. However, the association between the baseline urinary uric acid (UUA) level and renal function decline remains unclear, and we aimed to assess this association. Methods In this retrospective cohort-controlled study, we included patients who met the following inclusion criteria: age > 18 years, the presence of at least one UUA level in their electronic medical records (EMR), and two eGFR values. The exclusion criteria were chronic dialysis treatment before the baseline eGFR or any history of kidney transplantation. The EMR of the patients have been retrospectively screened between 31st December 2001 and 31st January 2022. The study group consisted of patients with UUA levels of ≥750 mg/day. In the control group, we included patients whose every UUA level was <750 mg/day. The primary endpoint was a composite of eGFR decline of ≥50%, eGFR <15 mL/min, dialysis initiation, or death. Secondary endpoints were as follows: eGFR decline of ≥50%, the latest eGFR <15 mL/min, or death. The endpoints were compared between the groups by Cox proportional hazards model analysis. Results We included 480 patients in the study group and 2,998 in the control group. The primary end point was observed in 30.95% and 16.25% of participants in the control and study groups, respectively; however, after it was compared between the two groups using the Cox model, there was no significant difference (HR 1.20, 95% CI: 0.96-1.51, p = 0.11). Similarly, no significant differences in the rates of secondary endpoints between the two groups were observed, except the difference between the eGFR declines >50% which was significant, as was observed by the Cox model (HR 2.22, 95% CI: 1.47-3.37, p < 0.001). Conclusion There was no significant difference in the rate of the composite endpoint between the study and control groups. Kidney function deterioration (as measured by eGFR decline of ≥50%) was significantly higher among patients with baseline hyperuricosuria (UUA ≥750 mg/day) than in those with normal uricosuria, as was observed by the Cox model. Further prospective studies are needed to clarify the role of uricosuria in renal function deterioration.