Sex Differences in Admission Urine Culture Positivity, Pathogen Distribution, and Clinical Characteristics Among Patients with Calcium Oxalate Stones

Purpose: This study aimed to determine whether positive admission urine culture is associated with stone burden, renal involvement, pathogen distribution, and measured urinary biochemical profiles in men and women with calcium oxalate stones. Methods: We retrospectively analyzed adults who underwent percutaneous nephrolithotomy or ureterorenoscopy for upper urinary tract stones between 2016 and 2020. Calcium oxalate stones were defined as stones containing ≥50% calcium oxalate monohydrate and/or dihydrate by Fourier transform infrared spectroscopy. Patients were compared by sex and then stratified by admission urine culture status within each sex. Results: Among 1,257 patients, 878 were men and 379 were women. Women had a higher culture-positive rate than men (59.6% vs. 28.2%, p < 0.001), despite lower 24-hour urinary calcium, uric acid, sodium, potassium, phosphorus, and chloride. In men, culture positivity was associated with recurrent stones, renal stone location, larger maximum stone diameter, and lower eGFR, but not with measured 24-hour urinary parameters. In women, culture positivity was associated with renal stone location, larger maximum stone diameter, lower eGFR, and modestly lower urinary calcium. Escherichia coli predominated among culture-positive women, whereas men showed a broader pathogen distribution. Conclusions: Positive admission urine culture was associated with greater stone burden and renal involvement in calcium oxalate stone disease, without a uniformly higher measured urinary biochemical profile. Culture status may provide clinically relevant phenotypic information alongside measured urinary biochemical assessment, although interpretation is limited by the absence of key CaOx-related urinary parameters such as oxalate, citrate, and supersaturation indices.