In recent years, tolvaptan - a vasopressin V2 receptor antagonist and the first drug approved specifically for the treatment of ADPKD - has become an important treatment option for decreasing renal decline in patients with rapid disease progression [6,15]. The Mayo Clinic ADPKD classification scheme is one of the screening tools used to predict future progression, using total kidney volume as a prognostic factor [3,15]. This evidence concerns the gene AVPR2 and autosomal dominant polycystic kidney disease.