Natural history of simple and complex cysts in autosomal dominant polycystic kidney disease on MRI

Kidney volume, reflecting cumulative effects of many cysts, is an important prognostic biomarker for autosomal dominant polycystic kidney disease (ADPKD) but fails in many patients. Tracking individual cysts may more directly assess disease progression. Individual cysts (n = 299) from 37 subjects were evaluated retrospectively over ≥ 8 years by serial MRI (mean follow-up = 11 years). Cysts were labeled on every available MRI scan, totaling 1654 contours (median timepoints per cyst = 5). Effects of cyst location, morphology, and growth pattern on kidney function decline were evaluated by univariate and multivariate analyses. Simple, T2-bright cysts follow logistic growth (median cyst growth rate = 11%/year). A subset (94/222, 42%) transitions over time to shrinking, to complex solid-fluid/fluid-fluid cysts, then to homogeneously T1-bright cysts and finally disappearing. By contrast, T1-bright complex cysts have no volume change (median cyst growth rate = 0%/year; p < 0.001). On multivariate analysis, faster kidney function decline is associated with simple cyst diameter > 2 cm on index scan (p = 0.007) and simple cyst transitions (p = 0.02). There is a trend towards faster kidney function decline with higher simple cyst growth rate (p = 0.16). Profiling individual cysts on serial MRI to identify transitions as well as size and growth rate may improve predictions of ADPKD progression and treatment response. Polycystic kidney disease causes the growth of many fluid-filled sacs called cysts in the kidneys. Cysts can enlarge the kidneys and lead to kidney failure, requiring dialysis and/or kidney transplantation. It is important to be able to determine whether the disease is progressing so that patients may be treated appropriately. In many patients, doctors keep track of the disease by measuring kidney size using special images known as MRI scans. This doesn’t work for all patients. In our study, we analyzed MRI scans from different patients to see if we could use information from individual cysts, instead of measuring kidney size overall, to determine how the disease is advancing. We learned that specific changes in individual cysts may relate to kidney function. This could provide another tool for tracking disease progression in patients with polycystic kidney disease. Hu et al. track 299 kidney cysts from 37 ADPKD subjects on 203 MRI scans over 8+ years of follow-up to explore their natural history. Cyst diameter predicts kidney function decline and simple cysts follow logistic growth, periodically transitioning to shrinking, hemorrhaging, or disappearing with transitions.