Presentation Authors: Derek Frank*, Ali Aldoukhi, William Roberts, Khurshid Ghani, Adam Matzger, Ann Arbor, MI
Introduction: Human kidney stones are complex materials which contain a mineral component dispersed in an organic/protein matrix. We aimed to develop an artificial model to replicate the chemical and physical properties of kidney stones with the goal of providing the field with an artificial stone model that can be used as a surrogate for human stones when optimizing laser lithotripsy procedures. The fragmentation behavior of these artificial stones was compared to human kidney stones and characterized using controlled, single-pulse Holmium laser lithotripsy experiments.
Methods: To mimic human calcium oxalate monohydrate (COM) kidney stones, artificial calcium stones were prepared by dispersing COM (the main constituent of COM kidney stones) in organic polymer. Composite stones were prepared by evaporating polymer solutions in a mortar and pestle containing COM while grinding and pressing the resulting material in a hydraulic press at five tons for two minutes. Human COM kidney stones (>95% COM) were sectioned using a diamond saw (Model 650, South Bay Technology) to 2-3 mm thickness prior to lithotripsy. Fragmented crater volumes for both artificial and sectioned human stones were compared using single pulse lithotripsy experiments with a 120 W Holmium laser (Lumenis; 1.0 J per pulse) and measured using a digital 3D microscope (Hirox RH-2000).
Results: Artificial kidney stones prepared with 20 wt% polymer showed fragmentation behavior similar to human kidney stones (Figure 1). This behavior is in sharp contrast to artificial stones containing only COM, which disintegrate in water. Furthermore, these composite stones improve on other artificial stone models such as the BegoStone, which are composed entirely of material foreign to human kidney stones such as gypsum plaster.
Conclusions: A new artificial kidney stone composed of a composite material of COM and an organic polymer is an accurate model for holmium laser lithotripsy of human COM stones. Further work is needed to refine these models and expand to other human kidney stone types.
Source of Funding: Boston Scientific Research Grant