Indapamide and Chlorthalidone to Reduce Urine Supersaturation for Kidney Stone Prevention

Inclusion criteria: * Written, informed consent. * Age 18 years or older. * Recurrent kidney stone disease (≥2 kidney stone episodes in the last 10 years prior to randomisation). * Past kidney stone containing ≥50 % CaOx, CaP, or a mixture of both. Exclusion criteria: * Patients with secondary causes of recurrent calcium kidney stones including severe eating disorders (anorexia or bulimia), chronic bowel disease, intestinal or bariatric surgery, sarcoidosis, primary hyperparathyroidism, chronic urinary tract infection. * Patients with the following medications: Thiazide or loop diuretics, carbonic anhydrase inhibitors (including topiramate), xanthine oxidase inhibitors, alkali, active vitamin D (calcitriol or similar), calcium supplementation, bisphosphonates, denusomab, teriparatide, sodium-glucose co-transporter 2 (SGLT2) inhibitors, strong CYP3A4 inhibitors or inducers (may affect indapamide metabolism), lithium (To be eligible for study participation, patients taking any of the above listed medications at screening must be willing to discontinue these medications at least 28 days before randomization). * Patients with chronic kidney disease (defined as CKD-EPI eGFR \<30 mL/min). * Patients with glomerulonephritis. * Patients with the following biochemical imbalances: severe hypercalcemia (\>2.8 mmol/L), therapy-resistant hypokalemia or conditions with increased potassium loss, severe hyponatremia (\<130 mmol/L), symptomatic hyperuricemia. * Patients with hepatic encephalopathy or severe liver insufficiency. * Patients with severe cardiac insufficiency. * Patient with a recent cerebrovascular event. * Patients with a solid organ transplant. * Pregnant and lactating women (A urine pregnancy test must be performed for women of child-bearing potential, defined as women who are not surgically sterilized/hysterectomized, and/or who are postmenopausal for less than 12 months). * Previous (within 3 months prior to randomization) or concomitant participation in another interventional clinical trial. * Previous participation in INDAPACHLOR. * Inability to understand and follow the protocol. * Allergy to any one of the study drugs.