Prognostic Implications of Urinary Potassium to Creatinine Ratio in Patients With Predialysis Chronic Kidney Disease: A Cohort Study.

OBJECTIVES: Although a low or high serum potassium level in chronic kidney disease (CKD) is associated with worsening renal function and increased cardiovascular disease (CVD) events, urinary potassium excretion has been found to predict adverse health outcomes with conflicting results. We conducted a cohort study to determine whether urinary potassium to creatinine (K/Cr) ratio is an independent risk for further deterioration in renal function or increased CVD events. METHODS: We identified 650 predialysis patients with CKD hospitalized for an educational program regarding CKD between January 2010 and December 2018. The study outcomes were CKD progression and incident CVD events, with baseline urinary K/Cr ratio categorized into quartiles-Q1, < 19.8; Q2, 19.9-27.7; Q3, 27.8-37.9; and Q4, > 38.0. RESULTS: During follow-up (median, 35 months), 509 CKD progressions and 129 incident CVD events were identified. Sixty two patients died during follow-up. Multivariate Cox proportional hazard model showed that after adjustment for demographic factors and laboratory data, patients in Q1 had a 2.02-fold higher risk of worsening renal function than those in Q4 (95% confidence interval, 1.50-2.71; P < .001), whereas urinary K/Cr ratio had no association with the incidence of CVD events. Similarly, inverse probability weighting analysis showed an increased risk of CKD progression in the lowest quartile. Furthermore, the association between low fractional excretion of potassium and worsening renal function was confirmed. CONCLUSION: A low urinary K/Cr ratio is independently associated with worsening renal function but not with a risk of incident CVD event in predialysis patients with CKD.

The effect of sodium zirconium cyclosilicate on acid-base balance in chronic kidney disease.

Hyperkalemia is a common electrolyte abnormality in chronic kidney disease (CKD). Sodium zirconium cyclosilicate (SZC) is a novel selective cation exchanger that is used to treat hyperkalemia and may also capture ammonium, which is of a similar size to potassium. We investigated the effect of SZC on acid-base balance in CKD patients. This retrospective study surveyed 20 patients with CKD whose serum potassium levels were maintained within the normal range by treatment with polysulfonate resin, which was replaced with SZC during the clinical course. We compared clinical parameters before and after changing medications. Changing the potassium binder from polysulfonate resin to SZC increased serum bicarbonate (p = 0.016) and decreased blood urea nitrogen (p = 0.017). Serum potassium levels were maintained within the normal range. Urine pH, anion gap, and osmolality gap were unchanged during treatment. No gastrointestinal symptoms were noted during the observation period. Our data suggest that SZC may improve not only hyperkalemia but also metabolic acidosis by increasing the excretion of ammonium from the intestinal tract in patients with CKD. SZC could be a more suitable medication for CKD patients with hyperkalemia and metabolic acidosis.