The relevance of microbiology in the management of anorectal sepsis.

Eighty patients with anorectal sepsis were studied over three years. All abscesses were drained and pus was submitted for culture. If a fistula was found when the abscess was drained it was laid open otherwise a second examination under anaesthetic was performed within 7-10 days. In no case was sterile pus obtained. Gut aerobes, predominantly Escherichia coli, were isolated from 49 of 53 (92.5%) of patients with a fistula and 8 of 27 (29.6%) of those without. 'Gut-specific bacteroides' predominantly Bacteroides fragilis were isolated from 47 of 53 (88.7%) patients with a fistula and 5 of 27 (18.5%) of those without. Anaerobes not specific to the gut, predominantly B. asaccharolyticus, B. ureolyticus, peptococci and peptostreptococci, in the absence of those specific to the gut, were isolated from 2 of 53 patients with a fistula (3.8%) and 17 of 27 (63%) of those without. Staphylococcus aureus was isolated from only 1 of 53 (1.9%) patients with a fistula but from 8 of 27 (29.6%) of those without. It is concluded that only patients with gut-specific organisms should be submitted to a second examination under anaesthetic and that culture of pus in anorectal sepsis is an essential part of its management.