Antibiotic prescribing trends and outcomes in outpatient low-risk diverticulitis: a retrospective analysis in Veterans Health Administration between 2016 and 2023

Abstract

Abstract Background: Outpatient antibiotic prescribing remains common despite evidence that selective non-antibiotic management is safe for low-risk uncomplicated diverticulitis. Although recent guidelines recommend withholding antibiotics in selected patients, real-world prescribing patterns and associated outcomes remain unclear. Methods: We conducted a retrospective cohort study using nationwide Veterans Health Administration data (2016–2023) to identify emergency department visits for a first case of uncomplicated diverticulitis among patients discharged without admission. Low-risk diverticulitis was defined as age <65 years, Charlson Comorbidity Index <2, and white blood cell count <15 × 103/µL. Outcomes included antibiotic prescribing trends, assessed using linear regression, and one-year hospitalization for diverticulitis. Analyses for one-year hospitalization were stratified by age and comorbidity burden to assess effect modification. Subdistribution hazard (Fine-Gray) models estimated adjusted hazard ratios, accounting for the competing risk of death. Results: Among 4,249 patients with low-risk diverticulitis (median age, 51 yr; 84.6% male), 4,068 (95.7%) received antibiotics. From 2016 to 2023, the proportion managed without antibiotics remained unchanged (approximately 4%), while β-lactam use increased and fluoroquinolone use declined. Antibiotic use was not significantly associated with a reduced risk of one-year hospitalization (adjusted hazard ratio, 0.99; 95% confidence interval, 0.54–1.84; P = .99). No significant differences were observed across age-comorbidity strata or antibiotic classes, although subgroup analyses may have been underpowered. Conclusions: Despite guideline recommendations, antibiotics were prescribed for most low-risk patients with uncomplicated diverticulitis, with no change over eight years. Clinical outcomes did not differ by antibiotic exposure, highlighting an opportunity to reduce unnecessary antibiotic use through outpatient stewardship interventions.