Hypocitraturia: its importance as a factor in the development of urolithiasis
Piotr Skrzypczyk, Małgorzata Pańczyk-Tomaszewska
The citrate anion is an endogenous inhibitor of calcium deposits in the urinary tract. Moreover, by urine alkalisation, citrates enhance uric acid and cystine solubility. Hypocitraturia in adults is defined as excretion of citrates with urine below 320 mg/24 h. The most common definitions in children involve citrate excretion in 24 hour urine collection at a level <365 mg/1.73 m2/24 h in boys and <310 mg/1.73 m2/24 h in girls. Moreover, the urine citrate/creatinine ratio is also considered: for children aged 0–5 years <0.42 mg/mg and for children older than 5 years of age <0.25 mg/mg. Hypocitraturia is a common metabolic disturbance; such a diagnosis is made in approximately 20–60% of adults and 10–68% of children with urolithiasis. Various factors may affect citrate excretion with urine, the most significant of which is the pH value (of blood, urine or intracellular fluid). Most patients are diagnosed with so-called idiopathic hypocitraturia, although it also accompanies acidosis, including distal tubular acidosis, hypokalaemia, high-protein diet and treatment with certain medications (carbonic anhydrase inhibitors, angiotensin-converting enzyme inhibitors, thiazide diuretics). Patients with hypocitraturia should first and of foremost have dietary modifications introduced. This involves an increase in the dietary amount of fluids and citrus fruit as well as salt and protein restriction. Patients with recurring urolithiasis may also be recommended citrate products, the most common of which is potassium citrate. Citrus juices may be an alternative, but their effect is not as potent and unambiguous as in the case of commercially available citrate products.