Epitaxial relationships in urolithiasis: the brushite-whewellite system

Area of Science:

• Crystallization science
• Biomineralization
• Urology

Background:

• Kidney stones often contain calcium oxalate or calcium phosphate.
• The formation mechanisms of these stones are not fully understood.
• Heterogeneous nucleation plays a role in crystal formation in biological systems.

Purpose of the Study:

• To investigate the epitaxial nucleation of brushite by whewellite.
• To examine the induction of calcium oxalate precipitation by brushite.
• To understand the role of crystal interactions in stone formation.

Main Methods:

• Utilized metastable supersaturated solutions of calcium oxalate and calcium phosphate.
• Employed whewellite (calcium oxalate monohydrate) and brushite (calcium monohydrogen phosphate dihydrate) as nucleating agents.
• Performed scanning electron microscopy (SEM) to observe crystal nucleation and growth.

Main Results:

• Whewellite significantly accelerated brushite nucleation, reducing precipitation time by approximately 75%.
• Brushite crystals also induced calcium oxalate precipitation, though at a slower growth rate.
• SEM confirmed brushite originating from whewellite seeds and limited calcium oxalate nucleation on brushite.

Conclusions:

• Whewellite and brushite exhibit mutual epitaxial nucleation effects.
• These findings provide insights into the formation of mixed calcium oxalate and calcium phosphate stones in urine.
• Understanding these crystallization pathways can inform prevention and treatment strategies for kidney stones.