Urinary stones maybe composed of calcium oxalate monohydrate (COM, whewellite), calcium oxalate dihydrate (COD, weddellite), carbonate apatite (CA, dahllite), ammonium urate, magnesium ammonium phosphate (PAM, Struvite), calcium hydrogen phosphate dihydrate (brushite), uric acid (AU0 anhydrous form and AU2 dihydrate form, uricite) and its salts, cystine, xanthine, 2,8-dihydroxyadenine, and drugs .
No doubt that in very rare forms whose recognition can be only obtained with the FT-IR method (drugs or xanthine or 2,8-dihydroxyadenine stones) this is crucial for the rational treatment of the patient.
As it can be observed in Figure 2(a), the excessive adenine intake leads to the formation of 2,8-dihydroxyadenine (DHA) crystals, which is not observed in control animals.
This occurs because adenine is a substrate for XDH, which leads to the formation of an insoluble compound, named 2,8-dihydroxyadenine (DHA), that precipitates in tubule-interstitial compartment causing TIN .
Insoluble metabolites such as uric acid, xanthine, and 2,8-dihydroxyadenine cause urinary tract calculi and arthritis.
2,8-Dihydroxyadenine was a kind gift of Ragnhild Seip (Oslo, Norway).
2,8-Dihydroxyadenine (2,8-DHA) is excreted in urine and can precipitate in renal tissue and the urinary tract in patients with dihydroxyadeninuria attributable to adenine phosphoribosyltransferase (EC 184.108.40.206) deficiency (3).
Adenine phosphoribosyltransferase deficiency: 2,8-dihydroxyadenine lithiasis.
A fast and simple screening method for detection of 2,8-dihydroxyadenine
urolithiasis by capillary zone electrophoresis.
The imprecision of the method was tested by assaying eight samples of healthy volunteers with added 2,8-dihydroxyadenine (DHA; not present in normal urine) at three concentrations for 20 days.
 Nonstandard abbreviations: CD, cyclodextrin; AMP, 2-amino-2-methyl-1-propanol; UV, ultraviolet; SDS, sodium dodecyl sulfate; BGE, background electrolyte; OA, orotic acid; SAICAR, succinylaminoimidazole carboxamide riboside; SAR, succinyladenosine; DHA, 2,8-dihydroxyadenine; CE, capillary electrophoresis; UA, uric acid; HX, hypoxanthine; and X, xanthine.
For this reason, metabolites such as uric acid and 2,8-dihydroxyadenine
are NMR invisible.