The effect of pH on the risk of calcium oxalate crystallization in urine

Eur Urol. 1986;12(1):59-61. doi: 10.1159/000472578.


The risk of calcium oxalate (CaOx) crystallization at different pH levels was determined in urine from recurrent CaOx-stone formers and normal subjects. The highest crystallization risk was observed between pH 4.5 and 5.5. In the pH range 6.5-7.5, there was a marked increase in crystallization of calcium phosphate (CaP). The results suggest the beneficial effect of moderate alkalinization in terms of a reduced CaOx crystallization. Reduced CaOx crystallization occurs at the expense of an increased formation of CaP crystals. Whether this increases the risk of CaP-stone formation is not known, but the CaP crystals were usually small, at least below pH 7.5.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / urine
  • Calcium Oxalate / urine*
  • Calcium Phosphates / urine
  • Crystallization
  • Humans
  • Hydrogen-Ion Concentration
  • Oxalates / urine
  • Risk
  • Urinary Calculi / etiology*
  • Urinary Calculi / urine


  • Calcium Phosphates
  • Oxalates
  • alpha-tricalcium phosphate
  • tetracalcium phosphate
  • Calcium Oxalate
  • calcium phosphate, monobasic, anhydrous
  • calcium phosphate
  • calcium phosphate, dibasic, anhydrous
  • Calcium