MO435: The Prognostic Implication of 24-h Urine Urea Excretion With Renal Progression: Analysis of KNOW-CKD Study

Abstract BACKGROUND AND AIMS Urea excretion is the basic function of the nephron. However, its prognostic implication has been not extensively studied in a specific subpopulation of chronic kidney diseases (CKD). METHOD Total of 2232 patients in KNOW-CKD cohort were analyzed. Baseline characteristics were used as a prognosticator in the Cox regression model. For categorical comparison, tertiles of 24-h urea excretion were used as high, low and moderate excretion of urea. Linear modelling and nonlinear modelling based on restricted cubic splines were used to study the impact of 24-h urea excretion on renal survival. RESULTS Mean daily urea excretion was 8.2 ± 3.6 g/day. Mean daily urea excretion was 12.1 ± 3.1 g/day versus 4.8 ± 1.3 g/day in the high urea excretion group (HUG) and low urea excretion group (LUG) (P < 0.001). Mean eGFR of LUG was 47.0 ± 30.9 mL/min/1.73m2 and mean eGFR of HUG was 60.6 ± 29.9 mL/min/1.73m2 (P < 0.001). Serum albumin level was higher in HUG with 4.3 ± 0.4 g/dL versus 4.1 ± 0.5 g/dL of LUG (P < 0.001). Compared with HUG, LUG showed a hazard ratio of end-stage renal disease (ESRD) with 1.407 [95% confidence interval (CI) 1.115–1.774, P = 0.004] in the linear multiple regression model, which was adjusted by eGFR, age, gender, body mass index, type of CKD, proteinuria amount, systolic blood pressure, hemoglobin, blood urea nitrogen, serum albumin, serum cholesterol, serum uric acid, hsCRP, statin usage, renin-angiotensin-aldosterone system blocker usage. In the non-linear modeling, daily urea excretion showed a two-step change in log hazard ratio to ESRD. Threshold points of log hazard ratio among the whole study population were observed at 5 g/day and 15 g/day, respectively. The reduction of log hazard ratio in the HUG was more clear in the eGFR 30–60 mL/min/1.73m2 subpopulation (Figure 1C). Similarly, a reduction in log hazard ratio in the HUG was observed in glomerulonephritis, polycystic kidney disease subpopulations, but not in the diabetes mellitus nephropathy subpopulation (Figure 1D–F). CONCLUSION Daily urea urine excretion showed prognostic implications in the CKD stage 3 subgroups, glomerulonephritis subgroups and polycystic kidney disease subgroups. In the following researches, studies focusing on interventional targets in the context of daily urea excretion in those subgroups should be warranted.