Correlation of Calcium Metabolic Axis with Urinary Stone Characteristics

Urinary stone disease (USD) refers to the presence of stones or salt crystals within the urinary tract, with calcium stones accounting for approximately 80% of cases. Increased urinary calcium and phosphorus excretion predispose individuals to urinary stones, with hypercalciuria being the most significant risk factor. Vitamin D plays a pivotal role in modifying urine calcium and phosphorus excretion, and it enhances calcium and phosphorus reabsorption in the kidneys. Urinary stone disease is a recognized risk factor for chronic kidney disease (CKD) and may also lead to life-threatening complications such as perinephric abscesses, urosepsis, and urinary tract malignancies. The role of serum vitamin D and its effects on serum calcium and phosphorus in urinary stone formation have been subjects of controversy.

This study aims to evaluate the associations between serum calcium, phosphorus, and vitamin D levels and urinary stones.

This retrospective study involved two groups of 90 patients, one with urinary stones and the other without. Demographic and biochemical data, including serum calcium, phosphorus, and 25-(OH) vitamin D levels, were recorded for all patients. Patients were categorized into four groups based on their serum vitamin D levels: Excess, sufficient, insufficient, and deficient. The presence and characteristics of urinary stones were assessed using non-contrast CT scans.

The mean age of the patients was 54.62 ± 15.46 years. Laboratory investigations revealed mean serum calcium, phosphorus, and vitamin D levels of 9.56 ± 0.65 mg/dL, 3.53 ± 0.79 mg/dL, and 25.05 ± 12.96 ng/mL, respectively. This study demonstrated a significant correlation between serum calcium levels and the maximum diameter of urinary stones (correlation = 0.313, P-value = 0.005). No other significant associations were found between serum calcium, serum phosphorus, and serum vitamin D levels and the number of kidney stones, stone laterality, and type of kidney stone. There was also no significant difference between the two groups.

In conclusion, the role of serum calcium, phosphorus, and 25-(OH) vitamin D levels in urinary stone formation remains controversial. This study suggests that there is no significant association between serum calcium, phosphorus, or 25-(OH) vitamin D and urinary stones, except for a positive association between serum calcium and the diameter of the stone.