Hypocitraturia

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Hypocitraturia, a low amount of citrate in the urine, is an important risk factor for kidney stone formation.

Classification

Hypocitraturia usually is defined as citrate excretion of less than 320 mg/day, but this definition has been challenged as inadequate for recurrent stone formers.

• Severe hypocitraturia: citrate excretion of < 100 mg/day
• Mild-to-moderate hypocitraturia: citrate excretion of 100-320 mg/day

Other definitions;

• Urine citrate level < 220 mg/day for both men and women, regardless of age, or

• Urine citrate level < 115 mg/day in men and < 200 mg/day in women.

Pathophysiology

Citrate in the urine has long been recognized as an inhibitor of calcium salt crystallization. Citrate is the dissociated anion of citric acid, a weak acid that is both ingested in the diet and produced endogenously in the tricarboxylic acid cycle.

The mean urinary citrate excretion is 640 mg/d in healthy individuals.