The significant contribution group identified patients with secondary (blind) tracts, horseshoe fistulas, or abscesses undiagnosed at physical examination and examination under anesthesia; those with the location of the internal orifice different from that identified by physical examination; or those with the grade of the fistula assessed to be more advanced after preoperative MRI.
Detection of higher Parks grades, distance of external opening of the fistula from the anal canal, horseshoe fistulas, and complex fistulas are indicative of significant MRI contribution following clinical evaluation.
(23) Limitations of that study were the small number of suprasphincteric fistulas, and that the procedure was not applied in cases with horseshoe fistula.
(20) including 251 cases, the technique was found to have a high success rate in low transsphincteric and semi-horseshoe fistulas, but a low success rate in high transsphincteric and horseshoe fistulas. There were no cases of anal incontinence in that study.