OBJECTIVE Bacterial imprints are always observed on highly carbonated apatite kidney stones but not
struvite kidney stones. Struvite and carbonated apatite stones with a high CO3 2–/PO4 3– rate are
believed to develop from infections, but their structural differences at the mesoscopic scale lack
METHODS We investigated 17 urinary calculi composed mainly of struvite or carbonated apatite by Fourier
transform infrared, scanning electron microscopy, and powder neutron diffraction techniques.
RESULTS Carbonated apatite but not struvite stones showed bacterial imprints. If the same stone contained
both carbonated apatite and struvite components, bacterial imprints were observed on the
carbonated apatite but not the struvite part. Moreover, neutron powder diffraction experiments
revealed the crystal size of struvite stones were larger than that of carbonated apatite stones
(250 50 vs 50 nm).
CONCLUSION Bacterial imprints may appear more easily on kidney stones with small nanocrystals, such as
carbonated apatite than with large nanocrystals, such as struvite. This approach may help
identify bacteria contributing to stone formation, perhaps with negative results of urine