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Citric acid or citrates in urine: which should we focus on in the prevention of calcium oxalate crystals and stones?
Urol Res. 2002 Oct; 30(5):336-41.UR

Abstract

In order to distinguish between normocitraturia and hypocitraturia, the 24 h urine excretion value of citric acid is evaluated in relation to the established limit value of 2.5 mmol/day. We propose changing this widely-used excretion value to a "minimum contribution" of citric acid to the total urine's ionic strength, since the inhibitory effect of citric acid on crystallization depends on citrate anions being available to complex calcium ions or to associate with the crystal surface. A total of 71424 h-urine samples, taken from 74 healthy persons and 58 calcium stone formers, were investigated for pH, citric acid concentration ([CA]), and related relative calcium oxalate supersaturation (RS). Based on the Henderson-Hasselbalch-equation, the individual concentrations of the differently charged citrate anion species in each of the urines were calculated from the urinary pH and [CA]. From the anion concentrations determined, the contribution of the urine's citric acid to the total urine's ionic strength, ISCA, was calculated. Referring to the limit value of 2.5 mmol/day and assuming an average urine volume of 1.5 l/day, a hypothetical concentration limit of 1.67 mmol/l can be obtained. Grouping the samples into "stone-formers" and "non-stone-formers" as well as into three different ranges of RS revealed: (1). that the groups' median [CA]-values were below 1.67 mmol/l, and (2). that [CA] was not inversely associated with the risk of stone formation. Within the pH-range of 5 and 7, the ISCA-values which are related to, for example, [CA]=1.67 mmol/l, vary considerably by a factor of nearly three between 2.48 mmol/l and 6.64 mmol/l. The use of a fixed citric acid excretion level for the distinction of normocitraturia from hypocitraturia does not take into account the different citrate species which actually modify the urine's crystallization behaviour. The proposed ISCA approach takes this fact into consideration. From this parameter, a desirable "minimum impact of citric acid" can be derived. In a first approach, a potential ISCA-limit value, which currently distinguishes between urines indicated by a "normo-protective" impact and those indicated by a "hypo-protective" impact with respect to calcium oxalate precipitation, may be set at 2.48 mmol/l.

Authors+Show Affiliations

Division of Experimental Urology, Department of Urology, Bonn University, Sigmund-Freud-Strasse 25, 53105 Bonn, Germany, norbert.laube@ukb.uni-bonn.deNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

12389124

Citation

Laube, Norbert, et al. "Citric Acid or Citrates in Urine: Which Should We Focus On in the Prevention of Calcium Oxalate Crystals and Stones?" Urological Research, vol. 30, no. 5, 2002, pp. 336-41.
Laube N, Jansen B, Hesse A. Citric acid or citrates in urine: which should we focus on in the prevention of calcium oxalate crystals and stones? Urol Res. 2002;30(5):336-41.
Laube, N., Jansen, B., & Hesse, A. (2002). Citric acid or citrates in urine: which should we focus on in the prevention of calcium oxalate crystals and stones? Urological Research, 30(5), 336-41.
Laube N, Jansen B, Hesse A. Citric Acid or Citrates in Urine: Which Should We Focus On in the Prevention of Calcium Oxalate Crystals and Stones. Urol Res. 2002;30(5):336-41. PubMed PMID: 12389124.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Citric acid or citrates in urine: which should we focus on in the prevention of calcium oxalate crystals and stones? AU - Laube,Norbert, AU - Jansen,Brigitte, AU - Hesse,Albrecht, Y1 - 2002/08/30/ PY - 2001/12/06/received PY - 2002/06/10/accepted PY - 2002/10/22/pubmed PY - 2003/6/26/medline PY - 2002/10/22/entrez SP - 336 EP - 41 JF - Urological research JO - Urol. Res. VL - 30 IS - 5 N2 - In order to distinguish between normocitraturia and hypocitraturia, the 24 h urine excretion value of citric acid is evaluated in relation to the established limit value of 2.5 mmol/day. We propose changing this widely-used excretion value to a "minimum contribution" of citric acid to the total urine's ionic strength, since the inhibitory effect of citric acid on crystallization depends on citrate anions being available to complex calcium ions or to associate with the crystal surface. A total of 71424 h-urine samples, taken from 74 healthy persons and 58 calcium stone formers, were investigated for pH, citric acid concentration ([CA]), and related relative calcium oxalate supersaturation (RS). Based on the Henderson-Hasselbalch-equation, the individual concentrations of the differently charged citrate anion species in each of the urines were calculated from the urinary pH and [CA]. From the anion concentrations determined, the contribution of the urine's citric acid to the total urine's ionic strength, ISCA, was calculated. Referring to the limit value of 2.5 mmol/day and assuming an average urine volume of 1.5 l/day, a hypothetical concentration limit of 1.67 mmol/l can be obtained. Grouping the samples into "stone-formers" and "non-stone-formers" as well as into three different ranges of RS revealed: (1). that the groups' median [CA]-values were below 1.67 mmol/l, and (2). that [CA] was not inversely associated with the risk of stone formation. Within the pH-range of 5 and 7, the ISCA-values which are related to, for example, [CA]=1.67 mmol/l, vary considerably by a factor of nearly three between 2.48 mmol/l and 6.64 mmol/l. The use of a fixed citric acid excretion level for the distinction of normocitraturia from hypocitraturia does not take into account the different citrate species which actually modify the urine's crystallization behaviour. The proposed ISCA approach takes this fact into consideration. From this parameter, a desirable "minimum impact of citric acid" can be derived. In a first approach, a potential ISCA-limit value, which currently distinguishes between urines indicated by a "normo-protective" impact and those indicated by a "hypo-protective" impact with respect to calcium oxalate precipitation, may be set at 2.48 mmol/l. SN - 0300-5623 UR - https://www.unboundmedicine.com/medline/citation/12389124/Citric_acid_or_citrates_in_urine:_which_should_we_focus_on_in_the_prevention_of_calcium_oxalate_crystals_and_stones L2 - https://dx.doi.org/10.1007/s00240-002-0272-3 DB - PRIME DP - Unbound Medicine ER -