The following is a summary of “Evidence of bacterial imprints in different types of non-struvite kidney stones,” published in the March 2025 issue of BMC Urology by Grases et al. 

Researchers conducted a retrospective study identifying bacterial imprints in apatite phosphate and mixed calcium oxalate/apatite phosphate stones, both lacking struvite.  

They examined 903 stones from 844 patients over 1 year using stereoscopic microscopy. Stone fragments underwent scanning electron microscopy with X-ray dispersive energy microanalysis and Fourier-transform infrared spectroscopy. When bacterial imprints were found, they analyzed the patient’s urine biochemically and bacteriologically. 

The results showed bacterial imprints in 8 renal stones without struvite, all with hydroxyapatite. Of these, 5 were primarily hydroxyapatite, 2 were mixed hydroxyapatite/calcium oxalate dihydrate, and 1 was a papillary calcium oxalate monohydrate stone with imprints at Randall’s plaque. Another was a cavity calcium oxalate monohydrate stone with hydroxyapatite in the core and bacterial imprints. 

Investigators identified bacterial imprints in non-struvite renal stones, always within a hydroxyapatite matrix. A urinary pH above 6.0 favored apatite phosphate formation and bacterial growth, highlighting the need for pH control to prevent bacteria-mediated stone formation. 

Source: bmcurol.biomedcentral.com/articles/10.1186/s12894-025-01755-1