Treatment of anorectal abscesses continues to revolve around early surgical drainage and control of perianal sepsis. Yet even with prompt drainage, abscess recurrence and postoperative fistula formation rates are as high as 40% within 12 months. These complications are thought to be associated with inadequate drainage, elevated bacterial load, or a noncryptoglandular etiology of disease. Postoperative antibiotics have been used to account for these limitations, but their use is controversial and only weakly supported by current guidelines due to low-quality evidences. The aim of the present study was to perform a systematic review and meta-analysis of the current literature to determine the role of antibiotics in prevention of anal fistula following incision and drainage of anorectal abscesses.
Literature search was conducted using Medline, EMBASE, Scopus, the Cochrane Library, and Web of Science databases from 1946 to April 2018. Search terms were "perianal OR anal OR fistula-in-ano OR ischiorectal OR anorectal AND abscess AND antibiotics" and was limited to human studies in the English language. Literature review and data extraction were completed using PRISMA guidelines. A total of six studies with 817 patients were included for systematic review. The weighted mean age was 37.8 years, 20.4% of patients were female, and the follow up ranged from one to 30 months. Antibiotic courses varied by study, and duration ranged from five to 10 days. Of included patients, 358 (43.8%) underwent management without antibiotics while 459 (56.2%) patients were treated with antibiotics. Fistula rate in subjects receiving antibiotics was 16% versus 24% in those not receiving postoperative antibiotics. Meta-analysis revealed a statistically significant protective effect for antibiotic treatment (3 studies, OR 0.64; CI 0.43-0.96; P = 0.03).
Antibiotic therapy following incision and drainage of anorectal abscesses is associated with a 36% lower odds of fistula formation. An empiric 5-10-day course of antibiotics following operative drainage may avoid the morbidity of fistula formation in otherwise healthy patients, although quality of evidence is low. Further randomized trials are needed to fully clarify the role, duration, and type of antibiotics best suited for postoperative prevention of fistula following drainage of anorectal abscesses.