The role of routine flexible sigmoidoscopy in patients presenting with fistula-in-ano: an observational study

Flexible sigmoidoscopy is useful to look for an underlying aetiology in fistula-in-ano. This study was aimed to assess the yield of routine flexible sigmoidoscopy in patients presenting with fistula-in-ano. A retrospective analysis of 159 consecutive patients with fistula-in-ano who underwent routine flexible sigmoidoscopy was performed. Sigmoidoscopy findings were recorded on a standard uniform format using a computer database. Those with a known aetiology were excluded.

The median age was 39 (range: 14-74) years and the majority were males (n = 128, 80.5%). Forty-nine patients (30.8%) presented with a recurrent fistula-in-ano. On flexible sigmoidoscopy, internal opening was seen in only 23 patients (14.4%). Furthermore, incidental findings of haemorrhoids (n = 5, 3.1%) and polyps (n = 7, 4.4%) were found. One patient (0.6%) had a healed anal fissure, 5 patients (3.1%) had inflamed mucosa and 2 patients (1.3%) had ulcers. Only two patients with inflamed mucosa were diagnosed to have Crohn's disease on histology. Therefore, flexible sigmoidoscopy was not helpful in the majority to locate the internal opening. Only two patients had evidence of an underlying aetiology, which was Crohn's disease. However, they had recurrent complex fistulae and other associated symptoms. Therefore, flexible sigmoidoscopy may be reserved for selected group of patients with symptoms of an underlying aetiology.