Anorectal sepsis: microbiology in relation to fistula-in-ano.

One hundred and sixty-five patients presented in a 4-year period: 68 (41.2 per cent) had had previous anorectal sepsis and in 56 of these patients (82.3 per cent) the presenting sepsis was at the site of the previous abscess. The abscesses were drained and pus was sent for culture; any fistula, if found, was laid open. A second examination under anaesthesia was performed within 7--10 days if no fistula had been found. The pus from 114 patients grew bowel-derived organisms; 62 (54.4 per cent) fistulas were found. The pus from 34 patients grew skin-derived organisms but no fistula was demonstrated in this group. It is suggested that a second examination need only be performed if culture of the pus grows bowel-derived organisms: anorectal abscesses which grow skin-derived organisms are not associated with a fistula.