Urinary Stone Analysis

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