The anatomy of a jackstone: a novel morphometric analysis of a rare urinary calculus.

Jackstone calculi are rare urinary stones characterized by multiple spiculated arms, yet the mechanisms underlying their distinctive morphology remain incompletely understood, in part due to the challenge of quantifying microstructural growth patterns along their complex three-dimensional geometry. In this study, we applied a non-destructive micro-computed tomography morphometric method to analyze a jackstone retrieved from the bladder of a human donor. This approach enabled measurement of incremental layering along individual arms and branches. We hypothesized that distal arm regions would show evidence of more rapid remodeling than proximal regions. Consistent with this hypothesis, six of seven arms and four of six branches demonstrated greater layer number and decreased layer thickness toward their distal tips, supporting an abrasion-mediated remodeling model of jackstone growth. The donor also exhibited marked prostate enlargement and bladder wall hypertrophy, suggesting chronic urinary stasis as the physiological setting that permitted stone retention and arm development. These findings refine existing conceptual models by indicating that abrasion influences layer remodeling frequency rather than increasing protein layer thickness. The imaging and analytic workflow described here provides a reproducible framework for future structural, biochemical, and microbial investigations into jackstone pathogenesis.