Postoperative antibiotics for prevention of fistula-in-ano after drainage of a first anorectal or perianal abscess: a systematic review and meta-analysis

Abstract Background Anorectal or perianal abscess is usually treated by incision and drainage. However, some patients later develop fistula-in-ano, which may require further treatment and follow-up. Antibiotics are sometimes prescribed after drainage, but routine use remains controversial. We evaluated whether systemic antibiotics given around incision and drainage reduce later fistula-in-ano after a first cryptoglandular anorectal or perianal abscess. Methods PubMed, Embase, Scopus, Web of Science, and the Cochrane Library were searched through June 2026. Randomized and comparative observational studies comparing systemic antibiotics with no antibiotics, placebo, or standard care and reporting fistula events were eligible. Risk ratios (RRs) were pooled using random-effects models with Paule-Mandel and Knapp-Hartung, with subgroup analyses by follow-up duration, study design, and antibiotic regimen. Results The review included 11 comparative studies involving 2,191 patients. Antibiotics were not associated with a statistically significant reduction in later fistula formation (RR, 0.83; 95% confidence interval (CI), 0.58–1.19). Studies classified as having follow-up ≤ 3 months favored antibiotics (RR, 0.47; 95% CI, 0.34–0.64), whereas studies classified as ≥ 12 months showed no clear association (RR, 0.97; 95% CI, 0.48–1.98). Ciprofloxacin-based regimens showed a lower risk estimate (RR, 0.46; 95% CI, 0.33–0.63). Conclusions Current comparative evidence does not support routine systemic antibiotics solely to prevent fistula-in-ano after drainage of a first presumed cryptoglandular anorectal abscess. The apparent benefit in short-term follow-up and ciprofloxacin-based studies should be interpreted cautiously because of heterogeneity and potential confounding by design and outcome timing. Selective antibiotics for standard indications remain appropriate. Trial registration PROSPERO CRD420261358758; registered 08 April 2026.