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

## TL;DR

This study uses advanced imaging to analyze the unique structure of rare jackstone urinary stones and suggests that abrasion influences their growth patterns.

## Contribution

A novel non-destructive micro-CT morphometric method was applied to study jackstone calculus growth patterns.

## Key findings

- Distal regions of jackstone arms showed more rapid layer remodeling compared to proximal regions.
- Layer thickness decreased toward the tips of the stone arms, supporting an abrasion-mediated growth model.
- Chronic urinary stasis, indicated by prostate enlargement and bladder wall hypertrophy, likely enabled stone retention and arm development.

## Abstract

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.

The online version contains supplementary material available at 10.1007/s00240-026-01968-5.