Evidence for aggregation in oxalate stone formation: Atomic force and low voltage scanning electron microscopy

Purpose: The aim of this investigation was to differentiate between aggregation and crystal growth by studying the structure of oxalate stones at high spatial resolution using recently developed microscopy techniques. Materials and Methods: Sections from 6 complete human oxalate stones and 4 stone fragments were prepared by ultramicrotomy and examined by both low voltage scanning electron microscopy and atomic force microscopy. Results: The scanning electron microscopy showed lamellar structures up to 10 μm. in size, consistent with previous results, and provided evidence that these structures were composed of smaller particles. The atomic force microscopy clearly showed arrays of the small particles, whose size varied between 500Å and 2800Å. Conclusion: Our images suggest that an ordered aggregation of small crystallites is responsible for oxalate stone formation.