Methods The prospective one-year study was conducted on 34 ADPKD patients with creatinine clearance≧50 ml/min/1.73m2. Prior to the enrollment, 30 patients annually evaluated TKV and 24-hour urine for more than one year. Patients were divided into high (H-, n = 18) and free (F-, n = 16) water-intake groups. Total kidney volume (TKV) was measured at the beginning and end of the study. Twenty-four-hour urine and blood were analyzed every four months.