Serum calcium-magnesium-phosphate-potassium metabolic dysregulation in nephrolithiasis: predictive model development and mechanistic insights.

PURPOSE: To explore the pathophysiological interplay of serum calcium, magnesium, phosphate, and potassium (Ca, Mg, P, K) homeostasis in nephrolithiasis and establish an integrated risk prediction framework incorporating these routine homeostatic biomarkers. METHODS: This retrospective, hospital-based case-control study enrolled 611 patients with radiologically confirmed nephrolithiasis and 624 strict gender-matched controls to eliminate sex-related baseline biases. Fasting morning serum biochemical data were analyzed. Multivariable logistic regression identified core risk determinants. Model performance was rigorously validated through receiver operating characteristic (ROC) analysis, calibration curves, and decision curve analysis (DCA), followed by the construction of a diagnostic nomogram. RESULTS: The predictive model based on electrolyte indices demonstrated exceptional discriminative capacity (AUC = 0.812, 95% CI: 0.789-0.836) and high calibration accuracy (Brier score = 0.177, Hosmer-Lemeshow p = 0.852). Key independent predictors included an elevated serum calcium magnesium ratio (Ca/Mg, aOR = 5.50), increased calcium phosphate product (Ca×IP, aOR = 1.82), hypokalemia (aOR = 0.13), BMI ≥ 24, and reduced hemoglobin levels. DCA confirmed the model's net clinical benefit across a wide range of threshold probabilities. CONCLUSION: Dysregulation of serum Ca, Mg, P, K homeostasis is strongly associated with nephrolithiasis. Our nomogram may offer a complementary, blood-based initial assessment when 24-hour urine testing is not feasible, pending further validation.