Spot Urine-guided Salt Reduction in Chronic Kidney Disease Patients

Abstract

Objective: Dietary salt restriction is important in patients with chronic kidney disease (CKD) to reduce hypertension, cardiovascular events, progression of CKD, and mortality. However, recommending salt reduction for patients is difficult without knowing their actual sodium intake. This study evaluated the effectiveness of spot urine-guided salt reduction in CKD outpatients.

Design: A prospective cohort study was used.

Subjects: This study included a total of 127 adult outpatients (aged 60 ± 18 years, 80 males) with CKD. Their baseline estimated glomerular filtration rate was 51.4 ± 25.1 (mL/minute/1.73 m²), and 64 (50%) of them were with CKD stage 3a or 3b (both 32 [25%]).

Intervention: We informed the patients of their individual spot urine-estimated salt intake every time they visited the outpatient clinic. Based on the data, the nephrologist encouraged the patients to achieve their salt restriction goal.

Main outcome measure: The primary outcome was the estimated salt excretion, and the secondary outcome was the urinary protein-to-Cr ratio (UPCR). Multiple regression analyses were performed to clarify the contributing factors of changes in both outcomes.

Results: Over a follow-up of 12 months, the median number of patients' visits was 7 (5-8). The estimated salt intake was significantly reduced from 7.98 ± 2.49 g/day to 6.77 ± 1.77 g/day (P < .0001). The median UPCR was also reduced from 0.20 (0.10-0.80) to 0.10 (0.10-0.48) (P < .0001). On multiple regression analysis, a reduction in UPCR was positively associated with the baseline UPCR and a reduction in systolic blood pressure significantly (P < .0001 and P < .01, respectively) as well as positively correlated with a reduction in the estimated salt intake, with borderline significance (P = .08).

Conclusions: Providing spot urine-estimated salt intake feedback effectively motivated CKD patients to reduce their salt intake. Spot urine-guided salt reduction may slow CKD progression through decreased urinary protein excretion.