Hypercalciuria: principles of differential diagnostics

Hypercalciuria is the main lithogenic metabolic disorders in patients with calcium urolithiasis. This metabolic sign could be seen most often with other metabolic risk factors of urolithiasis (hyperuricosuria, hyperoxaluria, hypocitraturia and hypomagniuria). Pathogenetic mechanisms of hypercalciuria development are manifold, which provide basis for different forms of hypercalciuria. Excessive secretion of the calcium within urine is a consequence of the alterations in the functions of gastrointestinal system, kidneys, disbalance of some hormonal substances, regulating the bone metabolism; disturbances in the metabolism of vitamin D, genetic mutations and influence of alimentary factors. There are up to 7 main types of hypercalciuria known; every type is capable of increasing the risk for calcium oxalate or calcium phosphate stone formation. Moreover relatively many forms of symptomatic hypercalciuria are known (e.g., by granulomatous diseases, paraneoplastic syndromes, hypervitaminosis D etc.), which should be properly diagnosed. Therefore the differentiated approach is needed to diagnostics and optimal anti-recurrence therapy selection with calcium urolithiasis. In current guidelines attention is paid to the diagnostic algorithms and methodologic approaches to the diagnostics of the main hypercalciuria types, for example absorptive hylercalciuria of I, II, II and IV types, renal hypercalciuria, resorption hypercalciuria, hypercalciuria associated with renal tubular acidosis of the type I. The characteristic criteria are presented, typical for every type of hypercalciuria, and also the diagnostic schema for the patients with hypercalciuria.