Yu ASL, et al. - In a 14-year observational cohort study (The Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease study), researchers assessed the trajectories of glomerular filtration rate (GFR) decline in 241 adults with autosomal dominant polycystic kidney disease (ADPKD). Taking into account baseline age and magnetic resonance imaging measurements of total kidney volume (TKV) according to the method of Irazabal, 5 subclasses of participants were defined, as an estimate of the rate of kidney growth. Using mixed polynomial models, they reconstructed and fitted GFR trajectories spanning over four decades of life. For validation, they used data from the HALT-PKD study. Findings revealed a nonlinear GFR decline in ADPKD. A single measurement of kidney volume could predict GFR decline trajectory throughout adulthood. The possible utility of these models was suggested for clinical prognostication, clinical trial design, and patient selection for clinical interventions. Growth in kidney volume was causally related to GFR decline. The use of TKV as a surrogate endpoint in clinical trials was supported.