Surgical treatment and risk of recurrence of horseshoe anorectal abscess

Gaertner WB, et al. The American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Management of Anorectal Abscess, Fistula-in-Ano, and Rectovaginal Fistula. Dis Colon Rectum. 2022 Aug 1;65(8):964-985. Full-text for Emory users.

Patients with acute anorectal abscess should be treated promptly with incision and drainage. Grade of recommendation: strong recommendation based on low-quality evidence, 1C.

“Abscesses that cross the midline (ie, horseshoe) can be challenging to manage. These abscesses most often involve the deep postanal space and extend laterally into the ischiorectal spaces. [40,71] Under these circumstances, primary lay-open fistulotomy should typically be avoided because these fistulas tend to be transsphincteric. The Hanley procedure, a technique that drains the deep postanal space and uses counter incisions to address the ischiorectal spaces, is effective in the setting of a horseshoe abscess, [71] although it may negatively impact anal sphincter function. [40,71] A modified Hanley technique using a posterior midline partial sphincterotomy to unroof the postanal space plus seton placement has a high rate of abscess resolution and has been reported to better preserve anorectal function compared to other operative interventions. [40,72,73]” (p. 969)

“After drainage, abscesses may recur in up to 44% of patients, most often within 1 year of initial treatment. [2,10,70] Inadequate drainage, the presence of loculations or a horseshoe-type abscess, and not performing a primary fistulotomy are risk factors for recurrent abscess (primary fistulotomy is further addressed in recommendation no. 4). [10,71,72]” (p. 969)

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Types of perirectal abscesses

One discussion this week involved perirectal abscesses.

Reference: Calandrella C, La Gamma N. Abscess, Perirectal. In StatPearls [NCBI Bookshelf]. Last updated: 2018 Oct 27.

Summary: Although often thought of as the same, perianal abscess and perirectal abscesses differ in both complexity and care options. Except for perianal abscess which can be simply incised and drained as definitive care, all others usually require intravenous antibiotics, surgical evaluation, and drainage. A majority of abscesses are diagnosed clinically based on skin findings and palpitation of the affected area alone, but some require advanced imaging to determine the extent of infiltration.

A perirectal abscess can be further divided into a category based on anatomical location: ischiorectal abscess, intersphincteric abscess, and supralevator abscess. Given the variability in location and severity of the abscess, it is important to consider the presence of fistulas or tracts which may contribute to the spread of the infection. Perianal abscesses are the most common type, followed by ischiorectal, and intersphincteric abscesses.

Alternatively, the Park’s classification system which groups the fistulas into 4 types based on the course of the fistula and the relationship to the anal sphincters.

  • Intersphincteric (70%): Between the internal and external sphincters
  • Trans-sphincteric (25%): Extends thru the external sphincter into the ischiorectal fossa
  • Suprasphincteric (5%): Lasses from the rectum to the skin through the levator ani
  • Extrasphincteric (1%): Extends from the intersphincteric plane through the puborectalis

EPIDEMIOLOGY: The incidence of anorectal abscesses is 1:10,000, resulting in approximately 68,000 to 96,000 cases in the United States per year with a male prevalence of 3:1 during the third and fourth decades of life. The condition is seen more in the summer and spring months. Although often a concern of the patient, data does not support that there is an increased risk from hygiene, anal-receptive intercourse, diabetes, obesity, race, or altered bowel habits.