Pathophysiology
Clinical meaning
Kidney stone recurrence prevention is grounded in modifying the urinary chemical environment to reduce supersaturation of lithogenic solutes and enhance protective inhibitors. The 24-hour urine metabolic evaluation is the cornerstone of personalized prevention, quantifying the key stone-promoting factors (calcium, oxalate, uric acid, sodium, volume, pH) and protective factors (citrate, magnesium) that determine crystallization risk. Supersaturation โ the ratio of dissolved solute concentration to the thermodynamic solubility product โ is the fundamental physical-chemical driver: when supersaturation exceeds the formation product (upper limit of metastability), spontaneous crystallization occurs. Each dietary and pharmacological intervention targets specific components of this equation. Increased fluid intake (targeting urine output greater than 2.5 L/day) is the single most effective intervention, diluting all solute concentrations and reducing supersaturation across all stone types. Dietary sodium restriction (less than 2300 mg/day) reduces urinary calcium excretion because sodium and calcium share reabsorption pathways in the proximal tubule โ every 100 mEq of sodium excreted obligates approximately 25 mg of additional calcium loss. Dietary calcium should be maintained at 1000-1200 mg/day from food sources, consumed with meals: intestinal calcium binds dietary oxalate,...