Predictors for Positive Repeated Urine Culture in Patients with Negative Initial Urine Culture before Endoscopic Lithotripsy

Background: Few studies investigated whether a pre-operative repeated urine culture (RUC) was needed to reduce the risk of post-operative infection in patients with negative initial urine culture (UC). Our objective was to identify predictors for positive RUC in patients with negative initial UC before endoscopic lithotripsy. Methods: We retrospectively included 358 patients with urinary stone and negative initial UC who received RUC prior to endoscopic lithotripsy between November 2020 and October 2022. Uni-variable analysis and multi-variable logistic regression analysis were performed to identify risk factors of pre-operative positive RUC. A nomogram was further established as a predicted model to comprehensively evaluate the risk of positive RUC. Results: RUC was found to be positive in 9.8% of patients (35/358). Gram-negative bacteria were the predominant pathogens. The incidence of systemic inflammatory response syndrome (SIRS) was significantly higher in patients with positive RUC (3/35, 8.6%) than that of patients with negative RUC (6/323, 1.9%, p = 0.048), and there was a trend that patients with positive RUC had a higher incidence of urosepsis (2/35, 5.7% vs. 3/323, 0.9%; p = 0.077). Multi-variable logistic regression analysis showed that female (odds ratio [OR] = 2.71, 95% confidence interval [CI]: 1.21–6.09, p = 0.016), age >65 years (OR = 2.69, 95% CI: 1.15–6.33, p = 0.006), positive urine leukocyte esterase (ULE) (OR = 4.88, 95% CI: 2.04–11.63, p < 0.001), and positive nitrite (OR = 11.21, 95% CI: 3.10–40.51, p < 0.001) were independent risk factors for positive RUC. Conclusions: Positive RUC was associated with an increased risk of post-operative infectious complications in patients with urinary stones and negative initial UC. Female, age over 65 years, positive ULE, and positive nitrite were independent risk factors for positive RUC. We first developed the nomogram to identify those patients with positive RUC, which may assist clinicians to provide individualized recommendations for RUC prior to endoscopic lithotripsy.