[Mixed-nucleus renal calculi]

We made a crystallographic analysis of 87 mixed-nucleus stones and found 4 groups of stones of this kind, which are as follow: urico-oxalic, oxalico-uric, phosphato-oxalic and oxalic-phosphatic. We did not find any mixed-nucleus, urico-phosphatic or phosphatico-uric stones and we explain this fact according to the known lithogenic, metabolic mechanisms, in which urinary pH has an important function.