A Simple Protocol to Effectively Manage Anal Fistulas with No Obvious Internal Opening

Abstract

Purpose: In some anal fistulas, the internal/primary opening cannot be located even after examination and assessment on MRI or transrectal ultrasound. The efficacy of a simple new protocol to manage such therapeutically challenging fistulas was tested.

Patients and methods: All anal fistula patients operated consecutively over 7 years were included in the study. A simple two-step protocol was followed for fistulas in which the internal opening was not locatable after clinical examination and MRI assessment. First, the MRI was reassessed. The site where the fistula was closest to the internal sphincter was noted. It was assumed that the internal-opening was located at that position and the fistula was treated accordingly. Second, in horseshoe anal fistulas with no apparent internal opening, it was assumed that the internal opening was located in the midline. Low fistulas were treated by fistulotomy and high fistulas by a sphincter-sparing procedure. Incontinence was evaluated by objective incontinence scores (Vaizey scores).

Results: A total of 757 patients were operated (median follow-up-33 months). Of these, 57 patients were excluded due to short or inadequate follow-up. In 154/700 (22%) patients, the internal opening could not be located while in 546/700 (78%), the internal opening was found. Both the groups were similar in all parameters. In the "internal-opening found" group, the fistula healed completely in 486/546 (89%) and in the 'internal-opening not found group', the fistula healed in 140/156 (90.9%) (p=1.01). The objective continence scores did not change significantly after surgery in both the groups.

Conclusion: This new protocol seems effective as a high cure rate could be achieved in 'internal-opening not found' fistulas which was comparable to fistula healing in the 'internal-opening found' group.

Keywords: MRI; anal fistula; fistula-in-ano; horseshoe; internal opening; recurrence.

Figure 1

The protocol to manage anal fistulas in which the internal opening was not found by conventional methods and MRI.

Figure 2

MRI-axial sections in a 56-year-old male with transsphincteric fistula at 3 o’clock position and the internal opening in the anal canal at the posterior midline. Upper panel – T2, lower panel – Short tau inversion recovery (STIR) (Yellow arrows are showing fistula tract).

Figure 3

MRI-axial sections in a 30-year-old male with low transsphincteric anal fistula at 5 o’clock position. The tract traverses through both external and internal anal sphincters and opens in the anal canal at the posterior midline position. Upper panel – T2, lower panel – STIR (Yellow arrows are showing fistula tract, blue arrow are showing the internal sphincter, red arrow are showing the external sphincter).

Figure 4

MRI-axial-STIR sections in a 26-year-old male with high intersphincteric fistula from 11o’clock to posterior midline piercing the internal sphincter and opening in the anal canal at the posterior midline. Upper panel – T2, lower panel – STIR (Yellow arrows are showing fistula tract).

Figure 5

MRI-axial-STIR sections in a 51-year-old male with low transsphincteric fistula at posterior midline position. The tract is penetrating the external but not the internal sphincter and is not seen opening in anal canal. (Yellow arrows are showing fistula tract).

Figure 6

MRI-axial sections in a 52 year-old-male with high transsphincteric fistula in the right ischiorectal fossa with fistula tract reaching the external sphincter at 9 o’clock but not piercing external and internal sphincters and not opening in anal canal. Upper panel – T2, lower panel – STIR (Yellow arrows are showing fistula tract).

Figure 7

MRI- axial sections in a 28-year-old female with posterior intersphincteric horseshoe fistula and high transsphincteric abscess in the left ischiorectal fossa with NO clear internal opening. Upper panel – T2, lower panel – STIR (Yellow arrows are showing fistula tract, blue arrows are showing high transsphincteric abscess).

Figure 8

Intraoperative wound after TROPIS (transanal opening of intersphincteric space). (A) Schematic diagram of anal fistula and anal canal, (B) Schematic diagram showing the intersphincteric portion of the fistula tract (green colour) and an artery forceps inside the internal opening about to be laid open with electrocautery, (C) Schematic diagram showing the intersphincteric portion of the fistula tract laid open with electrocautery, (D) Intersphincteric space distal (inferior) to the internal opening laid open by a vertical incision, (E) Intraoperative photograph of a patient after a complete TROPIS procedure showing the TROPIS wound in the anal canal and a tube inserted in the tract in left ischiorectal fossa. The tube sutured to the skin with monofilament non-absorbable suture (2–0 nylon). (F) Intraoperative photograph showing the TROPIS wound in the anal canal.

Figure 9

A 55-year-old male patient with a recurrent high transsphincteric anal fistula with multiple tracts. (A) Axial section (Schematic diagram), (B) Coronal section (Schematic diagram), (C) Pre-operative photograph (D) MRI-axial section-low level (T2), (E) MRI-coronal section-low level (T2), (F) Post-operative photograph showing TROPIS wound (laid open intersphincteric portion of the fistula tract) in the anal canal. (G) MRI-axial section-high level (T2), (H) MRI-coronal section-high level (T2), (I) Post-operative photograph showing the final picture (TROPIS wound in the anal canal) and a tube inserted in the tract in left ischiorectal fossa. The tube sutured to the skin with monofilament non-absorbable suture (2-0 nylon) (Yellow arrows are showing fistula tracts).

Figure 10

A 34-year-old male patient with a high horseshoe transsphincteric anal fistula and abscess. (A): Axial section (Schematic diagram), (B) Coronal section (Schematic diagram), (C) Post-operative photograph showing TROPIS wound (laid open intersphincteric portion of the fistula tract) in the anal canal. (D) MRI-axial section (STIR), (E) MRI-coronal section (STIR), (F) Post-operative photograph showing the final picture (TROPIS wound in the anal canal) and a tube inserted in the tract in left ischiorectal fossa. The tube sutured to the skin with monofilament non-absorbable suture (2–0 nylon) (Yellow arrows are showing fistula tracts).