Importance of Calcium-Based Scales in Kidney Stone

Calcium oxalate (CaOx) crystals are major constituent of over 80% kidney stones and are often found mixed with calcium phosphate (CaP) and other crystalline minerals. Idiopathic CaOx stone formation starts with deposition of CaP crystals within the renal interstitium. These deposits grow by accretion of more CaP crystals with assistance of collagen fibers. Growing deposits eventually reach papillary surface epithelium and develop into subepithelial Randall's plaques. Heterogeneous nucleation of CaOx crystals on the exposed CaP plaques produces CaOx stones. In some cases, retention of crystals in tubular lumen lead to blockage of ducts of Bellini producing so-called Randall's plugs, which, once exposed to pelvic urine, become nidus for stone formation. Crystal formation, retention, and deposition are regulated by forces that promote (e.g., supersaturation) and those that inhibit (e.g., various macromolecules). Stone formation is a multifactorial and multistep process. Thorough analyses of patient's urinary biochemistry are necessary for effective disease management.