BACKGROUND: Hyperkalemia is one of the more serious complications of chronic kidney disease (CKD), and the cause of potassium retention is a reduction in urinary potassium excretion. However, few studies have examined the extent of the decrease of urinary potassium excretion in detail with respect to decreased renal function. METHODS: Nine hundred eighty-nine patients with CKD (CKD stages G1 and G2 combined: 135; G3a: 107; G3b: 170; G4: 289; and G5: 288) were evaluated retrospectively. Values for urinary potassium excretion were compared between CKD stages, and the associations between urinary potassium excretion and clinical parameters, including diabetes mellitus status and use of renin-angiotensin-aldosterone system inhibitors, were analyzed using a multivariable linear regression analysis. RESULTS: Urinary potassium excretion gradually decreased with worsening of CKD (G5: 24.8 ± 0.8 mEq/d, P < 0.001 vs. earlier CKD stages). In contrast, the value of fractional excretion of potassium at CKD G5 was significantly higher than that at the other stages (30.63 ± 0.93%, P < 0.001). Multivariable linear regression analysis revealed that urinary potassium excretion was independently associated with urinary sodium excretion (standardized coefficient, 0.499), the estimated glomerular filtration rate (0.281), and serum chloride concentration (-0.086). CONCLUSION: This study demonstrated that urinary potassium excretion decreased with reductions in renal function. Furthermore, urinary potassium excretion was mainly affected by urinary sodium excretion and estimated glomerular filtration rate in patients with CKD, whereas the presence of diabetes mellitus and use of renin-angiotensin-aldosterone system inhibitors were not associated with urinary potassium excretion in this study.
Diabetes Mellitus ; Glomerular Filtration Rate ; Humans ; Hyperkalemia ; Linear Models ; Potassium* ; Renal Insufficiency, Chronic* ; Renin-Angiotensin System ; Retrospective Studies ; Sodium

BACKGROUND: Mizoribine (MZR) is an immunosuppressive drug used in Japan for treating patients with lupus nephritis and nephrotic syndrome and has been also reportedly effective in patients with immunoglobulin A (IgA) nephropathy. However, to date, few randomized control studies of MZR are performed in patients with IgA nephropathy. Therefore, this prospective, open-label, randomized, controlled trial aimed to investigate the efficacy and safety of adding MZR to standard treatment in these patients, and was conducted between April 1, 2009, and March 31, 2016, as a multicenter study. METHODS: Patients were randomly assigned (1:1) to receiving standard treatment plus MZR (MZR group) or standard treatment (control group). MZR was administered orally at a dose of 150 mg once daily for 12 months. RESULTS: Primary outcomes were the percentage reduction in urinary protein excretion from baseline and the rate of patients with hematuria disappearance 36 months after study initiation. Secondary outcomes were the rate of patients with proteinuria disappearance, clinical remission rate, absolute changes in estimated glomerular filtration rate from baseline, and the change in daily dose of prednisolone. Forty-two patients were randomly assigned to MZR (n = 21) and control groups (n = 21). Nine patients in MZR group and 15 patients in the control group completed the study. No significant differences were observed between the two groups with respect to primary and secondary outcomes. CONCLUSION: The addition of MZR to standard treatment has no beneficial effect on reducing urinary protein excretion and hematuria when treating patients with IgA nephropathy.
Glomerular Filtration Rate ; Glomerulonephritis, IGA* ; Hematuria ; Humans ; Immunoglobulin A* ; Immunoglobulins* ; Japan ; Lupus Nephritis ; Nephrotic Syndrome ; Prednisolone ; Prospective Studies ; Proteinuria