Urinary lithogenic factors in urolithiasis patients with kidney disease and correlation with renal function

Patients with kidney disease have a high incidence of kidney stones, yet the specific mechanisms remain elusive. The purpose of this study was to explore the connection between urinary lithogenic factors and renal function.

We retrospectively analyzed 150 patients with kidney disease -associated nephrolithiasis and 84 stone-forming patients with common nephrolithiasis. The renal disease group comprised 69 renal transplant recipients, 36 patients with CKD stages 1-2, and 45 patients with CKD stages 3-4. Urinary lithogenic factors and renal function indicators were compared and correlated.

Patients with kidney disease showed significantly higher calcium/creatinine and magnesium/creatinine ratios, and lower citrate/creatinine ratios and urinary uric acid levels, compared to those with common nephrolithiasis (all P < 0.05). No significant differences were observed in oxalate/creatinine or phosphate/creatinine ratios. Multivariate analysis identified Scr, BUN, PCR, eGFR, calcium/creatinine, citrate/creatinine, magnesium/creatinine, and urinary uric acid as independent factors associated with renal disease-associated nephrolithiasis (all P < 0.05). The distribution of core lithogenic factors differed across renal disease subtypes: citrate/creatinine was the core factor in renal transplant recipients, whereas calcium/creatinine was the core factor in patients with CKD stages 1-2, with urinary uric acid as a secondary factor. The prevalence of hypocitraturia, defined as a urinary citrate-to-creatinine ratio < 0.22 mmol/mmol, was markedly elevated across all renal disease subgroups (93.5% in transplant recipients, 100% in CKD stages 3-4, and 88.9% in CKD stages 1-2) compared with 66.7% in the general nephrolithiasis group. Correlation analysis revealed that declining renal function was positively associated with calcium/creatinine and magnesium/creatinine ratios, and negatively associated with citrate/creatinine ratio (all P < 0.05).

Patients with kidney disease had increased urinary calcium and magnesium excretion and decreased citrate levels compared to people with common nephrolithiasis. Kidney disease is associated with distinct alterations in urinary lithogenic factors, particularly hypocitraturia, with subtype-specific patterns that may guide targeted prevention strategies. These findings were based on a cross-sectional assessment using a single first-morning urine sample adjusted for urinary creatinine and should be validated with 24-h urine metabolic evaluation in future studies.