‣ To be eligible to participate in this trial, patients must satisfy all of the following inclusion criteria:

⁃ Willing to participate and provide informed consent

⁃ Aged 18-70 years

⁃ Diagnosis of ADPKD based on radiological +/- genetic criteria as per Kidney Health Australia - Caring for Australians and New Zealanders with Kidney Impairment (KHA-CARI) Guidelines

⁃ eGFR equal to or greater than 38 mL/min/1.73m2 and \<90 mL/min/1.73m2

‣ And have either:

‣ 5(a) One or more risk factors of progression from the following:

• Bilateral kidney length equal to or greater than16.5 cm, or

• Total Kidney Volume (TKV) equal to or greater than 750 mL or height-adjusted TKV (htTKV) equal to or greater than 600 mL/m2, or

• Mayo class IC/D/E or Pro-PKD score equal to or greater than 6 OR 5(b) Evidence of Active progression

• Decline in eGFR equal to or greater than 5 mL/min/1.73m2 in one year, or

• Decline in eGFR equal to or greater than 3 mL/min/1.73m2 per year over five years or more. or

• Increase in htTKV/TKV of equal to or greater than 5% per year on at least 2 measurements in the past year, excluding any initial eGFR effect over the initial 3 months of tolvaptan commencement (if applicable) Note: Tolvaptan therapy must have been in place for at least 6 months with stable dose for at least 3 months.