Combined analysis of kidney stones by X-ray diffraction and electron microprobe

Oxalate, apatite, struvite, uric acid and cystine stones were routinely analysed by X-ray diffraction. A second analysis was performed by electron microprobe. The substances not detected by X-ray diffraction were apatite and struvite in oxalate and cystine stones. Oxalate was not found in uric acid stones because of insufficient routine sample preparation, but could be detected in a second X-ray analysis. Conclusions concerning the exact stone composition can only be reached after X-ray diffraction has been completed in conjunction with a second procedure, such as electron microprobe analysis. For clinical routine use X-ray diffraction is sufficient if adequate sample preparation is performed. The electron microprobe analysis provides further information about mixed phase formations (single or multiple layers, diffuse distributions etc.) and about inclusions in a phase, which have some clinical consequences.