Impact of Bedside Versus Operating Room Drainage on Outcomes of Perianal Abscess: A Two-Center Retrospective Cohort Study With Propensity Score Matching

Objective To compare 1-year outcomes of bedside and operating-room drainage of perianal abscesses using propensity score methods to address confounding by indication. Methods This two-center retrospective cohort included 303 adults undergoing drainage of perianal or anorectal abscesses. Because all bedside procedures involved perianal abscesses, comparative analyses were restricted to 271 patients with perianal abscesses who were potentially eligible for either drainage approach (183 bedside and 88 operating room). We performed 1:1 propensity score matching, inverse probability of treatment weighting (IPTW), and doubly robust analysis using nine baseline covariates. Results Propensity score matching yielded 76 pairs. Recurrent abscess occurred in 6.6% of operating-room and 13.2% of bedside patients (OR, 0.38; 95% CI, 0.10-1.41; P = 0.147), newly diagnosed anal fistula in 10.5% and 18.4% (OR, 0.50; 95% CI, 0.19-1.33; P = 0.166), and reoperation in 11.8% and 28.9%, respectively (OR, 0.28; 95% CI, 0.10-0.75; P = 0.011). The association with lower reoperation remained significant in the IPTW (OR, 0.33; 95% CI, 0.15-0.60; P < 0.001) and doubly robust analyses (OR, 0.20; 95% CI, 0.05-0.45; P < 0.001). Recurrent abscess and anal fistula consistently favored operating-room drainage, but their doubly robust findings were exploratory and hypothesis-generating because of low events-per-variable values (2.4 and 3.5, respectively). Conclusion A reduction in the co-primary outcomes was not established in the matched or IPTW analyses; their doubly robust findings are exploratory and hypothesis-generating. Reoperation, a prespecified secondary outcome, was consistently less frequent after operating-room drainage. Further prospective studies are warranted.