Postoperative Urinary Tract Infection after Senile Upper Urinary Tract Calculi Surgery: Pathogen Analysis and Construction of Risk Prediction Model

Objective: This study aimed to describe the etiological profile of postoperative urinary tract infection (UTI) in elderly patients with upper urinary tract calculi and construct a risk factor prediction model. Methods: The clinical data of elderly patients with upper urinary tract calculi who underwent surgery in our hospital from January 2024 to March 2025 were retrospectively analysed. The patients were divided into an infection group and a control group according to whether they developed UTI. The risk factors for secondary UTI in elderly patients after upper urinary tract calculi surgery were also examined. A multivariate logistic regression analysis was used to establish a risk prediction model, and a receiver operating characteristic (ROC) curve was drawn. All patients were randomly divided into a training set and a validation set at a ratio of 7:3 to evaluate the stability of the prediction model. Results: Among the 233 elderly patients, 54 (23.18%) developed postoperative UTI. Univariate analysis identified hydronephrosis severity, age, hospital stay, preoperative serum albumin and postoperative daily water intake as associated with UTI (p < 0.05). In the multivariate model, age and hydronephrosis severity remained independent risk factors, whilst high postoperative water intake and preoperative albumin were independent protective factors. An ROC model based on these four variables showed an area under the curve (AUC) of 0.85 (95% CI 0.78–0.93) in the training set (specificity 0.820, sensitivity 0.752) and 0.81 (95% CI 0.71–0.91) in the validation set (specificity 0.813, sensitivity 0.762). Hosmer–Lemeshow test indicated good model fit. Conclusions: Age, hydronephrosis severity, preoperative serum albumin and postoperative daily water intake are relevant factors for secondary UTI in patients with upper urinary tract calculi after surgery. Clinicians should intervene early for high-risk populations.