Renal potassium management in chronic kidney disease: Differences between patients with or without hyperkalemia

Abstract Introduction Hyperkalemia (HK) is a common electrolyte disorder in chronic kidney disease (CKD), mainly in the advanced stages. A positive potassium balance due to reduced renal excretory capacity is likely the main pathogenic mechanism of HK. Research into the relative role of each pathogenic element in the development of HK in CKD may help to implement more suitable therapies. Objective To investigate renal potassium handling in advanced CKD patients, and to determine the differences between patients with or without HK. Material and methods Cross-sectional observational study in adult patients with stage 4–5 CKD pre-dialysis. Selection criteria included clinically stable patients and the ability to collect a 24 h urine sample correctly. Blood and urinary biochemical parameters were analyzed including sodium and potassium (K). Fractional excretion of K (FEK) and K load relative to glomerular filtration (Ku/GFR) were calculated. HK was defined as a serum K concentration ≥5.5 mmol/l. Results The study group consisted of 212 patients (mean age 65 ± 14 years, 92 females) with a mean GFR of 15.0 ± 4.2 mL/min/1.73 m2. 63 patients (30%) had HK. Patients with HK had lower mean bicarbonate levels with respect to patients with normal K levels (NK) (20.3 ± 3.1 vs. 22.8 ± 3.2 mEq/l, P  Conclusions Although the K load relative to glomerular filtration (Ku / GFR) is an important determinant of HK in advanced CKD, the most noteworthy characteristic associated with HK in these patients was the limitation of compensatory urinary K excretion, as indicated by lower FEK.