Anal Fistula : Aspects of Aetiology, Diagnosis and Prognosis After Surgical Treatment

Abstract: Patients with idiopathic anal fistula (n=85) were compared with 215 control subjects, matched for age and sex, through a 180-item questionnaire. Obesity, smoking, constipation and bowel symptoms associated with IBS were more common in the patients.Endoanal ultrasound (EUS) and magnetic resonance imaging (MRI) were compared in the preoperative evaluation of anal fistula in 23 patients. For classifying the primary tract, EUS and surgical findings agreed in 14 cases, and MRI and surgery for 11: for identifying an internal opening, the corresponding figures were 17 and 10.Healing and sphincter function were studied in 42 patients operated with fistula excision and closure of the internal opening. Twenty-three patients healed primarily and another 10 after one re-operation, whereas nine required further surgery until healed. Anal resting pressure was reduced after three and 12 months, and squeeze pressure after 12 months.Eighty-three patients were randomised to surgery with or without application of gentamicin-collagen underneath the flap: 26/42 of patients randomised to gentamicin-collagen healed primarily compared with 21/41 of patients randomised to surgery only (n.s).Micro perfusion in the flap was studied by laser Doppler flowmetry during surgery in 16 patients. No correlation was seen between change in blood flow during surgery and non-healing/recurrence of the fistula.In conclusion, obesity, functional bowel symptoms and possibly smoking are more common in patients with idiopathic anal fistula than in the general population. Endoanal ultrasound is a useful tool in the preoperative evaluation of anal fistula. Advancement flap repair has a reasonably high primary recurrence rate and healing is not significantly improved by local application of gentamicin-collagen: impaired intraoperative blood perfusion of the flap is an unlikely reason for non-healing. A decrease in continence occurs also after this kind of surgery, probably due to an impaired internal anal sphincter function.