A Study to See if Tolvaptan is Safe in Infants and Children Who at Enrollment Are 28 Days to Less Than 18 Years Old With Autosomal Recessive Polycystic Kidney Disease (ARPKD)

This study is a multinational, multicenter, open-label, non-randomized trial. The study consist of three periods: Screening Period, Treatment period and Follow-up period. Tolvaptan has been demonstrated to delay the decline of kidney function in adults with rapidly progressing ADPKD (CKD stages 1 to 4), a closely related indication to ARPKD, as measured by estimated glomerular filtration rate (eGFR) and Total Kidney Volume (TKV). Participants in this study will be assigned to tolvaptan and followed for 24 months over the course of the study. The overall trial duration is expected to be approximately 5 years.