Trial of prescribed water intake in polycystic kidney disease

INTERVENTION: Group A‐ Standard treatment and ad libitum water consumption for 36 months. Group B‐ Standard treatment and prescribed water consumption for 36 months. The daily volume of water prescribed for Group B will be tailored for each participant. It will be based on calculation of free water clearance from the urine collected. It will also take into account the fluid loss, seasonal changes and physical activity of the participant. Participants will be asked to self‐monitor their fluid intake (using either a paper‐based diary or smart‐phone compatible website) and measure the gravity in their urine using a urine dipstick. Participants will be required to reply to short message service (SMS) sent twice weekly in the first six months, then monthly thereafter, to their mobile phones with the result of the urine dipstick test. Participants in Group B will be contacted by the study nurse/dietitian by telephone at weeks 1,3, 6, then monthly in Year 1 and 3‐monthly in Years 2‐3 to monitor adherence to water intake and if necessary adjust the water intake based on results from pathology tests and urine dipstick. Standard treatment is defined as generic approaches to slow the progression of chronic kidney disease; which include the standard care from the participants' usual physician. CONDITION: Autosomal Dominant Polycystic Kidney Disease (ADPKD) PRIMARY OUTCOME: Percentage annual rate of change in height‐corrected Total Kidney Volume (Ht‐TKV) from Baseline to 36 months. SECONDARY OUTCOME: Renal disease progession in ADPKD measured by the changes in biomarkers, including urinary, serum samples and 24 hour urine sodium and urate. Safety measured by monitoring adverse events. ; Hyponatraemia is a possible adverse event. This will be monitored regularly by monitoring blood sodium levels during the study. If the sodium levels go below a minimum level, the participant will be wtihdrawn from the intervention (but continued to be followed up) and appropriate medical management undertaken. Treatment acceptability measured by the proportion of patients reporting that water intake can be maintained life‐long. Treatment acceptability measured by the proportion of patients withdrawing from the study. Treatment adherence measured by proportion of patients with 24 hr‐urine osmolality <300 mosmol/kg at all timepoints Treatment adherence measured by proportion of times each patient (Group B) responds to SMS text messages (sent twice‐weekly during Months 0 to 6, and then monthly thereafter) within 12 hours requesting the results of the late‐afternoon urine specific gravity (SG) Treatment efficacy measured by change in markers of Kidney Disease Progression: Rate of eGFR decline; resting mean arterial pressure (MAP); urine albumin to creatinine ratio and kidney pain. Treatment efficacy measured by changes in markers of systemic arginine vasopressin (AVP) activity; serum copeptin and 24‐hour urine osmolality and volume. INCLUSION CRITERIA: 1. Adult patients (18‐65 years of age) providing informed consent 2. Adult patients with a diagnosis of ADPKD 3. eGFR of 30 mL/min/1.73m2 within 6 weeks of randomisation as determined by the chronic kidney disease epidemiology collaboration (CKD EPI) formula