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,  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)
Onaca N, Hirshberg A, Adar R. Early reoperation for perirectal abscess: a preventable complication. Dis Colon Rectum. 2001 Oct;44(10):1469-73. Full-text for Emory users.
Results: Forty-eight patients (7.6 percent of all drainage procedures) required reoperation within ten days of the original procedure. The main factors leading to reoperation were incomplete drainage (23 patients), missed loculations within a drained abscess (15 patients), missed abscesses (4 patients), and postoperative bleeding (3 patients). Incomplete drainage was more common with simple perirectal abscesses, whereas most overlooked collections were located posteriorly. Horseshoe abscesses were associated with a particularly high rate (50 percent) of operative failures. Neither preexisting perianal pathology nor systemic immunosuppressive disease contributed to early failures.
Conclusion: Surgical errors are the leading cause of early failures in the surgical treatment of perianal abscesses. These errors occur in a limited number of typical patterns and can therefore be identified and taught with an aim to decrease their occurrence.
Yano T, et al. Prognostic factors for recurrence following the initial drainage of an anorectal abscess. Int J Colorectal Dis. 2010 Dec;25(12):1495-8. Full text for Emory users.
Results: Of the total of 205 subjects, 74 experienced recurrence and 131 were cured (without recurrence). An investigation on the prognostic factors for recurrence revealed that the time from disease onset to incision was the only significant prognostic factor (p = 0.001). Sex, age, body mass index, method of anesthesia, abscess location, anatomic classification, use of a drain, and comorbid diabetes mellitus had no influence on recurrence. The cumulative cure rates were 68.7% for 1 year, 64.2% for 2 years, and 63.5% for 3 years.