Analysis of clinical factors for hyperoxaluria in patients with calcium oxalate stones: a single-center retrospective cross-sectional study.

BACKGROUND

Hyperoxaluria is associated with calcium oxalate (CaOx) stone disease and is assessed by quantitative urinary oxalate excretion. We aimed to identify routinely available clinical factors associated with concurrent study-defined hyperoxaluria among adults with CaOx stones.

METHODS

This single-center retrospective cross-sectional study included 385 adults with infrared-spectroscopy-confirmed CaOx stones who underwent stone surgery and completed at least one valid preoperative 24-hour urine collection 3-10 days before surgery between January 1 and December 1, 2024. Study-defined hyperoxaluria was urinary oxalate excretion ≥ 40 mg/24 h. The primary exploratory model used forward likelihood-ratio selection after univariable screening; a sensitivity model simultaneously included age, sex, body mass index, and the four factors retained by the stepwise model.

RESULTS

Hyperoxaluria was present in 132 of 385 patients (34.3%). In the primary stepwise model, hyperlipidemia (odds ratio [OR] 1.591, 95% confidence interval [CI] 1.031-2.457; P = 0.036), a positive urine nitrite test (OR 2.356, 95% CI 1.114-4.986; P = 0.025), diabetes mellitus (OR 1.811, 95% CI 1.055-3.109; P = 0.031), and at least two previous stone operations (OR 1.632, 95% CI 1.048-2.541; P = 0.030) were associated with hyperoxaluria. In the prespecified sensitivity model, all effect directions were unchanged, but hyperlipidemia was not statistically significant (OR 1.499, 95% CI 0.966-2.326; P = 0.071); the other three associations remained statistically significant.

CONCLUSIONS

In surgically treated adults with composition-confirmed CaOx stones, the stepwise model identified four concurrent correlates of study-defined hyperoxaluria, whereas sensitivity analysis indicated that the hyperlipidemia association was model-dependent. The associations with a positive urine nitrite test, diabetes mellitus, and at least two previous stone operations were more stable across models. These exploratory indicators may help prioritize confirmatory 24-hour urine testing where access is limited, but they cannot replace metabolic evaluation or establish causality.