Diuretic Testing in Chronic Kidney Disease

Inclusion Criteria for CKD subjects: * CKD stage G3 (creatinine-based eGFR 30-59 mL/min/1.73m2) during the last outpatient visit Inclusion Criteria for Healthy subjects: • eGFR within the expected range for age (a decline of 1 ml/min/1.73 m2 per year starting from age 40 is considered the normal age-related decline in kidney function Exclusion Criteria: * Known intolerance or allergy to the diuretics * Current systemic chemotherapy for malignancy * Kidney transplant recipient * Use of calcineurin-inhibitors * Life expectancy \< 12 months * Current immunosuppressive treatment for glomerulonephritis * Incapacitated subjects or subjects who are deemed unfit to adequately adhere to instructions from the research team * Hypokalemia or hyperkalemia (K+ \< 3.0mmol/L or K+ \> 5.5 mmol/L) at inclusion visit * Hypo- or hypernatremia (Na+ \< 130 mmol/L or Na+ \> 150mmol/L) at inclusion visit * Inherited tubulopathy as the cause of CKD * Autosomal dominant polycystic or tubulointerstitial kidney disease causing CKD * Clinically relevant heart failure (New York Heart Association class III or IV) * Therapy-resistant hypertension, defined as systolic blood pressure \> 180mmHg at the inclusion visit * Current treatment with inhibitors of Organic anion transporters: probenecid, pravastatin, cimetidine, cephalosporins, acetazolamide \[22\] * Active hepatitis during last outpatient visit * Liver cirrhosis in advanced stage (Child-Pugh B or C) * Active drug- or alcohol abuse * Not being able to tolerate a 28-day washout of one of the drugs interfering with diuretic testing. * Women who are pregnant, breastfeeding, or planning on becoming pregnant before the test day