Alternately, they will aggregate on nuclei of different substances which is termed heterogenous nucl eation . An example of heterogenous nucleation would be the deposition of calcium phosphate on a calcium oxalate crystal. Deposition of calcium phosphate on a previously formed calcium phosphate crystal represents growth. As indicated above, crystal formation per se ie the initial central nidus, does not occur under metastable conditions. As a result crystal growth proceeds.
Small crystals evolve into large crystals.
Alternately, many small crystals aggregate to form crystal aggregates. Given this general background each of the five groups of renal stones i.e. calcium salts, uric acid, cystine oxalate and struvite, will now be overviewed in greater detail. Hypercalciuria is a frequent, but not universal finding. Of these individuals, a systemic or primary cause for the hypercalciuria can occasionally be documented. Table II below lists the more common entities associated with hypercalciuna, but is by no means an exhaustive list.