Citrates in nephrolithiasis: Hypocitraturia

18 Jul
2011

Low urinary citrate excretion is a common feature of idiopathic calcium stone disease. Several cut-off values have been pro­posed to classify hypocitraturia. In 1983, Nicar et al. defined hypocitraturia as a 24 hour citrate excretion lower than 320 mg (or 1.7 mmol) while other authors fixed the limit below the normal range. These different cut-off values may account for the wide range of hypocitraturia prevalence in nephrolithiasis, since it varies from 8% up to 68.3% in the liter­ature reports (Table II). Another factor which may account for these difference in prevalence is the possibility of considering hypocitraturia as a single metabolic alteration. In fact in a previous paper we found a hypocitraturia frequency, considered as a single metabolic derangement, of 12%, whereas, when con­sidering hypocitraturia together with hypercalciuria and/or hy- peruricosuria, this rate increased to 32%. Last but not least, the evaluation of urinary citrate excretion is highly influ­enced by food intake. Therefore a relevant difference in daily citrate excretion will occur according to whether patients are on their home diet or on controlled diet. A commonly accepted limit under which hypocitraturia may be diagnosed has been proposed by Pak. This Author suggested a “functional” definition of hypocitraturia which is a citrate ex­cretion lower than 320 mg/day. Online Pharmacy cialis professional

Notwithstanding the cut-off value adopted, several authors have described a higher rate of hypocitraturia in recurrent stone formers (41%) than in single stone formers (29%), as well as a higher urinary citrate excretion in pre-menopausal fe­males than in males and menopausal females. The daily urinary citrate to calcium ratio has also been used as a risk factor for stone formation. In fact it has been observed that patients with hypocitraturia, as a single metabolic alter­ation, showed higher urinary citrate excretion than those with several metabolic abnormalities. Moreover a higher rate of hypocitraturia was present also in stone formers with a very ac­tive calcium stone disease and/or low urinary citrate/calcium ratio. Welshman and McGeown found a calcium/citrate ratio in stone formers and normal subjects of 4.52 and 3.02 re­spectively, while in stone forming females this ratio was 3.54 and 1.41 in healthy females. Similar results were obtained in successive studies. Finally, Parks et al. examined the cit­rate/calcium ratio in 13 studies in which patients were man- tained on their home diet, and they found a clear difference be­tween renal stone formers and healthy subjects. Stone- forming females had higher urinary calcium and lower citrate than control females, whereas stone forming males presented a significantly higher urinary calcium excretion than normal subiects but only a small decrease in citrate excretion. Further­more, also the studies in which the patients ate controlled di­ets, showed, generally, a lower urinary citrate excretion in stone formers than in healthy subjects and these differences persisted when the subjects were considered separately ac­cording to sex. Finally, also in a recent paper, dealing with hypercalciuria and bone mass, we have found a higher urinary citrate excretion in females than in males (p=0.019) and the prevalence of hypocitraturia in the whole population was 25.5% (unpublished data).

Table II – Reported prevalence of hypocitraturia in patients with nephrolithiasis.

Authors

Prevalence

Year

Jaeger et al.

8.0%

1986

Caudarella et al.

12.6%

1986

Hess et al.

29.0%

2002

Hosking et al.

29.2%

1985

Khand et al.

29.2%

1994

Mossetti et al.

32.7%

2003

Caudarella et al.

32.8%

1996

Hobart and Hofbauer

34.0%

1991

Akinci et al.

46.6%

1991

Vahlensieck et al.

47.0%

1987

Pak et al.

50.0%

1987

Nicar et al.

55.0%

1983

Fardella et al.

68.3%

1994

top