Impact of 24-hour urine output trajectories on 28-day mortality in people with urinary tract infection: based on the MIMIC-IV database.

backgroundUrinary tract infection (UTI) is a common clinical infection that can lead to sepsis, infectious shock, and death when severe. Urine output is a critical indicator of renal function and hemodynamic status, and its trajectory may hold vital value for clinical outcomes in people with UTI.

objectiveTo investigate the association between 24-hour urine output trajectories and 28-day mortality in people managing UTI.

methodsThe data of individuals living with UTI were identified from the MIMIC-IV database. Latent class trajectory modeling (LCTM) classified urine output trajectories during the first 24 h post-ICU admission. The fitness of the model was evaluated using Bayesian Information Criterion (BIC), Akaike Information Criterion (AIC), Sample Adjusted Bayesian Information Criterion (SABIC), Entropy and Likelihood Ratio. Survival curves, Cox regression (adjusted for potential confounding factors: age, sex, race, marital status, vital signs, laboratory indicators, and all other available important clinical covariates), and restricted cubic splines (RCS) were used to analyze associations between trajectory groups and 28-day mortality (adjusted for all confounding factors). Effect modifications were explored by subgroup analyses.

resultsLCTM ultimately identified three types of urine output trajectories: Class 1 (5.57%): first decreased and then rebounded urine output; Class 2 (11.60%): continuous slow and stable increase in urine output, reflecting good renal perfusion and fluid balance; Class 3 (82.83%): continuous low urine output (0–1 mL/kg/h), with mortality rates of 92.6%, 94.8%, and 88.0%, respectively. Class 2 was significantly associated with reduced 28-day mortality risk compared to Class 3 group (HR = 0.479, 95%CI: 0.269–0.855, P = 0.013). Schoenfeld residual analysis confirmed that the model satisfied the proportional hazards assumption, and Bootstrap internal validation showed that the core risk ratio estimation was stable, which jointly supported the robustness of the main findings of this study. According to the stratified analysis, increased urine output during hours 12–24 post-admission correlated with lower mortality (HR < 1, P < 0.05). RCS revealed a nonlinear relationship between urine output during hours 6–12 and survival (P-non-linear = 0.0280).

conclusionDynamic 24-hour urine output changes significantly correlate with 28-day mortality in those with UTI, which underscores the clinical importance of urine output monitoring for optimizing treatment. CLINICAL TRIAL NUMBER: Not applicable.