Calcium Oxalate (CaOx) Urine Supersaturation in Calcium Stone Formers (CSF): Hypercalciuria versus Hyperoxaluria

Abstract

Calcium oxalate is the most frequent constituent of urinary calculi in idiopathic stone disease. Urinary excretion of both calcium (Ca) and oxalate (Ox) are recognised as risk factors¹; however, there is still disagreement on the relative role played by each of the two in the genesis of urine supersaturation for CaOx. On the one hand, it has been shown that stone recurrence is related to oxalate excretion but not to calcium excretion². On the other hand, it is widely recognized that reduction in Ca excretion (either by diet or with drugs) is highly effective in reducing the stone recurrence rate^3,4, even though Ox excretion may increase. This is because intestinal calcium absorption and Ca excretion are frequently increased in CSF and the decline in urinary calcium is typically more prominent than the modest increase in urinary oxalate³. The aim of our study was to evaluate CaOx urine supersaturation in relation to either Ca or Ox excretion in a large group of idiopathic CSF in an attempt to determine if either of the two has a more relevant clinical importance.