Does increased water intake prevent disease progression in autosomal dominant polycystic kidney disease?

Background. The clinical effects of increased water intake on autosomal dominant polycystic kidney disease (ADPKD) progression are unknown. Methods. ADPKD patients with creatinine clearance >= 50 mL/min/1.73 m(2) were divided into high (H-, n = 18) and free (F-, n = 16) water-intake groups, mainly according to their preference. Prior to the study, 30 patients underwent annual evaluation of total kidney volume (TKV) and 24-h urine for an average of 33 months. During the 1-year study period, TKV and 24-h urine were analyzed at the beginning and end of the study and every 4 months, respectively. Results. During the pre-study period, urine volume (UV) in the H-group was higher (P = 0.034), but TKV and kidney function and their slopes were not significantly different between the two groups. After the study commenced, UV further increased (P < 0.001) in the H-group but not in the F-group. During the study period, TKV and kidney function slopes were not significantly different between the two groups (primary endpoint). Plasma copeptin was lower (P = 0.024) in the H-group than in the F-group. TKV and kidney function slopes became worse (P = 0.047 and 0.011, respectively) after high water intake (H-group) but not in the F-group. High UV was associated with increased urine sodium, and urine sodium positively correlated with the % TKV slope (P = 0.014). Conclusions. Although the main endpoint was not significant, high water intake enhanced disease progression in the H-group when compared with the pre-study period. These findings necessitate a long-term randomized study before drawing a final conclusion.