FIGURE 2.

Mechanisms of CaOx stone formation. The first mechanism takes place within tubular lumens involving supersaturation of crystalline salts, crystallization, growth, self-aggregation, and adherence on tubular epithelial cells. Bacteria (both urease-producing and non–urease-producing groups) also play roles in this intratubular mechanism. The second mechanism initially takes place at renal interstitium by forming the so-called Randall plaque, which is a result of interstitial hydroxyapatite CaP crystal deposition and tissue inflammation. Some of the Randall plaques at and adjacent to the papillary tip can erode into the pelvicalyceal system, where CaOx is commonly supersaturated and crystallized. CaOx crystals subsequently deposit on the eroded Randall plaque, which then serves as the stone nidus, and the stone starts to form. CaOx, calcium oxalate; CaP, calcium phosphate; COM, calcium oxalate monohydrate; ECM, extracellular matrix.