Urinary stone analysis (stone analysis) is a procedure that reveals the exact composition of urinary stones. Guideline-based stone analysis is performed using Fourrier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), or polarized light microscopy. Urinary stones are caused by an imbalance in the physicochemical composition of urine with the formation of salt crystals. Many of the types of stones that can be found as a cause in urolithiasis form due to changes in urine pH. The following types of stones can be distinguished:
Cause of origin | Stone type | Frequency | Urine pH |
Acquired metabolic disorder | Calcium oxalate stone | 60-70 % | Alkaline or basic, depending on the cause |
Calcium phosphate stone (not associated with infection). | |||
Uric acid stone | 10 % | < 6,0 | |
Uric acid dihydrate stone | 2-5 % | ||
Calcium hydrogen phosphate dihydrate | 1 % | ||
Carbonate apatite stone | 5 % | > 7,0 | |
Urinary tract infection | Magnesium ammonium phosphate hexahydrate | 5-10 % | > 7,0 |
Carbonate apatite stone | 5 % | ||
Ammonium hydrogen urate stone/ ammonium urate stone | 0,5-1 % | ||
Calcium phosphate stone | 1 % | ||
Congenital metabolic disorder | Cystine stone | 0,5 % | < 6,0 |
Dihydroxyadenine stone | < 0,5 % | ||
Xanthine stone | < 0,5 % |
After the stone has been expelled, it should definitely be examined for its composition, as this is the only way to ensure safe and effective therapy and prophylaxis.
The procedure
Urinary stone analysis is performed using physical methods such as Fourrier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), or polarized light microscopy. These detect the composition of the respective stone on the basis of the absorption spectra of infrared rays, the various diffraction spectra of X-rays or polarization.The following parameters should be distinguished for the different types of stones:
Stone type | Chemical composition | Mineral name | Frequency | X-ray behavior |
Calcium oxalate | Calcium oxalate monohydrate | Whewellite stone | 60-70 % | shadowing |
Calcium oxalate dihydrate | Weddellite stone | 10-15 % | ||
Uric acid | Uric acid | Uricite | 10 % | not shading |
Uric acid dihydrate | 2-5 % | |||
Urate | Ammonium urate | 0,5-1 % | not shading | |
Calcium phosphate | Carbonatataptite | Dahlite | 5 % | shadowing |
Calcium hydrogen phosphate dihydrate | Brushite | 1 % | shadowing | |
Infection stone | Magnesium ammonium phosphate hexahydrate | Struvite | 5-10 % | weakly shading |
Cystine | Cystine | 0,5 % | Weakly shading | |
Rare stones | Dihydroxyadenine | < 0,5 % | not shading | |
Matrix stones | < 0,5 % | not shading | ||
Drug stones | < 0,5 % | not shading | ||
Xanthine | < 0,5 % | not shading |