Tolvaptan, a selective vasopressin V2 receptor antagonist, reduces pain in ADPKD patients with relatively preserved renal function by delaying the increase in kidney volume (a surrogate marker for disease progression), slowing the decline in renal function, and delaying the increase in kidney volume (a surrogate marker for disease progression). This evidence concerns the gene AVPR2 and autosomal dominant polycystic kidney disease.