Surgical assessment of acute anorectal sepsis is a better predictor of fistula than microbiological analysis.

Twenty-two patients with acute anorectal sepsis were examined prospectively to compare surgical assessment with microbiological analysis as predictors of the aetiology of the sepsis. Culture of gut organisms was a sensitive method of detecting an underlying fistula but was not particularly specific (80 per cent). Demonstration of sepsis in the intersphincteric space in association with an anorectal abscess was 100 per cent sensitive and 100 per cent specific for detection of an underlying fistula. The demonstration was facilitated by a radially placed incision.