Much of the current understanding of the natural history of ADPKD derives from the Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease (CRISP), an observational study now in its 19th year.6, 7, 8 In this study, patients with PKD1 had larger kidneys and more cysts than patients with PKD2, but the rate of growth of the kidneys was not significantly different, suggesting that the main difference between PKD1- and PKD2-associated disease is the number of cysts developing at a relatively early stage of disease, rather than their rate of growth.9 This evidence concerns the gene PKD2 and polycystic kidney disease.