Effect of inappropriate empirical antimicrobial therapy on time to hospital discharge in patients with community-acquired acute pyelonephritis: a propensity score-weighted retrospective cohort study

Acute pyelonephritis is a common reason for emergency department admission. The increasing prevalence of resistant pathogens has raised concerns about the effectiveness of empirical therapy and has led to increased use of broad-spectrum antimicrobial therapy. This study aimed to evaluate the effect of inappropriate antimicrobial therapy on the clinical outcome of time to hospital discharge among patients with community-acquired acute pyelonephritis treated at a hospital in Cartagena, Colombia. We conducted an analytical retrospective cohort study including adult patients admitted to the emergency department with a diagnosis of acute pyelonephritis who received empirical antimicrobial therapy at a hospital in Cartagena, Colombia, between January 2021 and August 2025. Inappropriate therapy was defined as resistance to the empirical antibiotic documented by urine culture. The primary objective was to compare time to hospital discharge between patients treated with appropriate antimicrobial therapy and those who received inappropriate therapy. A balanced pseudopopulation was created using inverse probability of treatment weighting (IPTW), and a Cox proportional hazards regression model was fitted to evaluate time to hospital discharge between groups. As a secondary outcome, the risk of 30-day rehospitalization due to urinary tract infection was assessed. Among the 321 cases included, 60 received inappropriate antimicrobial therapy. The median hospital lenght of stay was 2.64 days. The overall rehospitalization proportion was 13.7%. After IPTW adjustment, inappropriate therapy was not associated with longer time to hospital discharge (HR = 0.97; 95% CI 0.71–1.33) or with a higher risk of 30-day rehospitalization due to urinary tract infection (OR = 1.42; 95% CI 0.65–3.06). In patients hospitalized with community-acquired acute pyelonephritis, inappropriate empirical antimicrobial therapy was not associated with prolonged hospital stay or an increased risk of 30-day rehospitalization for urinary tract infection.