Improving the assessment and management of fistula-in-ano

Classical anal fistula surgery is both exploratory, to determine the extent of sepsis, and therapeutic. Imaging and novel surgical techniques have been employed to attempt to improve outcome, through sphincter conservation and by minimising relapse by detecting sepsis that might otherwise be missed at surgery. The impact of MRI in recurrent fistula-in-ano was studied in 71 patients. MRI-guided surgery reduced further recurrence by 75%, and surgeons always acting on MRI had fewer further recurrences than those ignoring imaging (p=0.008). Even in primary fistula, MRI had a therapeutic impact of 10%, precipitating surgery likely to reduce recurrence in a small, though important, proportion of patients. As surgery alone may be inaccurate, an outcome-derived reference standard was developed, allowing unbiased prospective comparison of preoperative fistula assessment. In 104 patients, anal endosonography (AES) was superior to digital examination. Whilst MRI was superior to both, AES provided accurate (91%) internal opening identification compared to MRI (97%), although MRI most accurately identified secondary extensions. A further study using three-dimensional AES found no benefit in extension localisation after hydrogen peroxide enhancement