The association of urinary sodium excretion and the need for renal replacement therapy in advanced chronic kidney disease: a cohort study

Abstract

BackgroundRestriction of dietary sodium is routinely recommended for patients with chronic kidney disease (CKD). Whether or not sodium intake is associated with the progression of CKD and mortality remains controversial. We evaluated the association of urinary sodium excretion (as a surrogate for sodium intake) on the need for renal replacement therapy and mortality in patients with advanced CKD.MethodsWe conducted a retrospective study of patients followed at a CKD clinic of a tertiary care hospital from January 2010 to December 2012. Adult patients with advanced CKD (estimated glomerular filtration rate (eGFR) <30 ml/min/1.73 m2) were included. Using a time-to-event analysis, we examined the association of urinary sodium excretion as a continuous and also as a categorical variable (categorized as low sodium diet - LSD (<100 mEq/day), medium sodium diet - MSD (100–150 mEq/day), and high sodium diet - HSD (>150 mEq/day) and the outcomes of interest. The primary outcome was defined as composite of progression to end-stage renal disease requiring any type of renal replacement therapy and mortality. The secondary outcome was change in eGFR/year.Results341 patients (82 LSD, 116 MSD and 143 HSD) were included in the study (mean follow up of 1.5 years) with a mean eGFR decline of 2.7 ml/min/1.73 m2/year. 105 patients (31 %) required renal replacement therapy and 10 (3 %) died. There was no association between urinary sodium excretion and change in the eGFR or need for renal replacement therapy and mortality in crude or adjusted models (unadjusted HR 1.002; 95%CI 1.000–1.004, adjusted HR 1.001; 95%CI 0.998–1.004).ConclusionIn patients with advanced CKD (eGFR < 30 ml/min/1.73 m2), sodium intake does not appear to impact the progression of CKD to end-stage renal disease; however, more definitive studies are needed.Electronic supplementary materialThe online version of this article (doi:10.1186/s12882-016-0338-z) contains supplementary material, which is available to authorized users.

High sodium intake increases blood pressure and risk of kidney disease. From the Science of Salt: A regularly updated systematic review of salt and health outcomes (August 2016 to March 2017)

“…The outcomes examined were diverse: Six studies assessed mortality outcomes, four studies assessed morbidity outcomes, three studies assessed outcomes related to symptoms/quality of life/functional status, studies assessed BP outcomes; eight studies assessed other clinically relevant surrogate outcomes; and nine studies assessed physiologic outcomes (Table ) . A range of outcomes were captured by the studies considered lower quality, including all‐cause mortality, gastric cancer, end‐stage renal disease requiring dialysis or transplant, cardiovascular events, hypertension prevalence, headaches/migraines, quality of life, multiple sclerosis, BP, cognitive function, osteoporosis risk and prevalence, nonalcoholic fatty liver disease, type 2 diabetes, carotid atherosclerosis, bone mineral density, changes in left ventricular mass, inflammatory markers, albuminuria, and other urinary markers . Most of these studies (n = 40) found adverse effects of dietary salt on health outcomes and benefits of a sodium‐restricted diet on health, except for 7 that were neutral and one reported worsening symptoms with a sodium‐restricted diet in the elderly …”

High and low sodium intakes are associated with incident chronic kidney disease in patients with normal renal function and hypertension

“…19-21 However, its association with renal function is less well investigated and confounding.Although several studies have shown that high dietary sodium intake increases the risk of CKD development or progression, 13,22-25 some results failed to find significant connections to renal outcome. 22,[26][27][28][29][30] In addition, although the adverse effects of increased dietary sodium on cardiovascular outcomes are more prominent in subjects with hypertension than in those without, 4,8,9 influence of hypertension on the relationship between sodium intake and CKD development is not known.…”

“…Although several studies have shown that high dietary sodium intake increases the risk of CKD development or progression, 13,[22][23][24][25] some results failed to find significant connections to renal outcome. 22,[26][27][28][29][30] In addition, although the adverse effects of increased dietary sodium on cardiovascular outcomes are more prominent in subjects with hypertension than in those without, 4,8,9 influence of hypertension on the relationship between sodium intake and CKD development is not known. Therefore, in order to investigate whether dietary sodium intake affects CKD development, this study assessed a prospective community-based cohort of subjects with normal renal function with and without hypertension.…”

Risk Reduction for End-Stage Renal Disease by Dietary Guidance Using the Gustatory Threshold Test for Salty Taste

“…Other reports have not indicated a significant association between urinary sodium and CKD progression or prognosis [18,19]. In addition, excessive salt restriction to less than 3 g per day increased the composite outcome of death and major cardiovascular events [20].…”