Under pressure: Anorectal abscesses… to drain or not to drain? | Department of Emergency Medicine

Resident Clinical Pearl

Victoria Landry

iFMEM R3

Reviewed by Dr. J Mekwan

Copy Edited by Dr. J Vonkeman

PDF Download: EMSJ Anorectal Abscess by VLandry

Case

A 57yo male presents to the emergency department with complaints of a lump near his rectum and pain with sitting which developed over the past week. He is afebrile with normal vital signs. He tells you that about 6 months ago this same thing occurred and drainage was attempted in the ED but was unsuccessful. A colorectal surgeon subsequently drained it successfully under local anesthetic in clinic later the same day. He has had no recurrence of symptoms until the past week. He smokes and has hypertension controlled with medication but is otherwise healthy.

He denies pain with defecation and has not had any rectal bleeding nor changes in bowel habits. He feels otherwise well and denies fevers or chills.

On exam you find a tender firm mass in the subcutaneous tissue lateral to his rectum on the left side. There is minimal overlying erythema and no fluctuance.

Key Point #1: Always do a Digital Rectal Exam

Palpate in all directions to localize area of tenderness¹
Should be unremarkable after you get past the anal verge² – if tenderness, mass, induration past anal verge, do a CT scan to assess for deeper abscess

You think back to your perirectal anatomy and recall the spaces where abscesses can develop.

Figure 1: Transverse anorectal anatomy³

Figure 2: Longitudinal anorectal anatomy³

	Perianal	Ischiorectal	Intersphincteric	Supralevator	Postanal
Incidence	40-45%	20-25%	20-25%	<5%	5-10%
Location	Outside anal verge, red, swollen, fluctuant, easily palpable at anal verge	Between rectum and ischial tuberosity, outside sphincters, palpable through rectal wall or lateral to anal verge on buttocks	Lower rectum, between sphincters, inferior to levator ani (tender indurated mass in rectum)	Above levator ani (tender indurated mass in rectum)	Posterior to rectum, Deep to external sphincter, inferior to levator ani
Symptoms	Painful perianal mass	Buttock pain	Rectal fullness, throbbing, worse with defecation	Perianal and buttock pain	Rectal fullness and pain near coccyx
Fever, ↑WBC	No	Possibly	Possibly	Yes	Yes
Fistula formation	++	+	+++	+++	–
ED I&D	Yes	Possibly: I&D/needle aspiration only if abscess is superficial and fluctuant	No	No: Consult surgery for urgent drainage	No

Table 1: Types of abscesses³

** caution as mass may be bigger/deeper than anticipated – prudent to defer to surgery for their expertise

Figure 3: Anorectal abscess locations⁴

Key Point #2: Get a CT scan to define the abscess for any of the following²

Unable to see the abscess superficially
Patient is unable to tolerate the DRE due to significant pain
Induration, bogginess or tenderness in the supralevator space (above the sphincter muscle)
If the extent of the abscess is uncertain⁴

Note: can use POCUS to evaluate location of abscess, but caution against false reassurance as to extent/depth, and safer to rely on palpable fluctuant mass to determine if I&D is safe

Figure 4: Perianal abscess on CT¹

Management⁵

Simple, isolated, fluctuant perianal abscess⁴
- Bedside I&D
- Goal is to relieve the pus under pressure²
Ischiorectal abscess²
- Can consider I&D only if superficial, but prudent to get a CT first
- Consult surgery for their expertise
Intersphincteric, Supralevator, Postanal
- CT to define the abscess
- Consult surgery

Key Point #3: Err on the side of caution

Only do I&D in the ED if the following criteria are met³ [3]

Perianal abscess (+/- ischiorectal) is small and superficial
Patient
- Is Well-appearing
- Is Cooperative
- Has no complicating factors (DM, immune compromise etc.)

Incision and Drainage of simple perianal abscess²

Local anesthetic – lidocaine with epinephrine
- Infiltrate superficial skin where you will poke with needle
- occasionally procedural sedation is needed³
Needle poke +/- aspiration (18guage) or pinpoint incision over painful region to localize purulent pocket⁴
Inject more local anesthetic²
Enlarge the incision
- Make incision as close to anal verge as possible to minimize the length of any potential fistula^2,5,6
- Cruciate (with trimming of the flaps) or elliptical incision over fluctuant part of abscess is preferred over a linear incision to keep incision open and draining without painful packing²
- If linear only, will need packing to prevent premature closure
- Note: loop drainage technique not recommended for I&D in the ED⁷
Break up loculations with finger (increased tactile feedback and better control) or hemostat +/- irrigation with saline⁷
Cover with bulky dressing⁴
Ideally, close follow up until complete healing (up to 8wks) to monitor for recurrence and for fistula formation⁵
Uncomplicated perianal abscesses do not require antibiotics after successful drainage².

Figure 5: Cruciate incision⁴

Instruct the patient to WASH⁸

W – warm water sitz baths 5-10min BID-QID PRN, with Epsom salts (start the day after I&D)
- Water >40°C helps decrease anal canal pressure
A – analgesics (NSAIDs, topical 1-2% lidocaine gel)
S – stool softeners (PEG, senna)
H – high fiber diet +/- fiber supplement
Uncomplicated perianal abscesses do not require antibiotics after successful drainage².

Indications for antibiotics (+/- tetanus +/- admission to hospital with surgical consult)⁴

Surrounding cellulitis
Immune compromise
Valvular heart disease
Diabetes
Systemic symptoms (Fever, ill appearing, leukocytosis)
Elderly

Note: Send off a wound culture before giving antibiotics

Antibiotic choice⁵:

Systemic: piperacillin-tazobactam
Oral: Amoxicillin-clavulanate or Metronidazole + ciprofloxacin

A word on fistulas

Fistulas are a connection between two epithelium-lined surfaces, characterized by persistent or recurrent anal drainage. They are seen in Crohn’s, TB, cancer, FB reactions, and as a complication of anorectal abscesses. Treatment is surgical³
~50% of anorectal abscesses form a fistula overtime²
Suggest surgical consultation after drainage of perianal abscess as fistula formation is common⁴
Fistulas may be missed on CT scan; MRI is more sensitive for diagnosis²

Take home points:

Always do a rectal exam as part of the initial evaluation
Have a low threshold to get a CT scan to define the abscess
Reserve I&D in the ED for perianal abscesses that are visible, superficial and fluctuant

References

Farah, Jennifer, Mason, Jessica, and Werner, Jessie, “Perirectal Abscess & Pilonidal Cyst.” [Online]. Available: https://www.emrap.org/episode/gastro/perirectal
Jhun, Paul and Cologne, Kyle, “Anorectal Infections,” HIPPO EMRAP, vol. 15, no. 9, pp. 17–18, Sep. 2015.
Parrillo, “Anorectal Emergencies,” presented at the EMRAP, Temple University Hospital EM Residency, Feb. 2004. [Online]. Available: https://www.emrap.org/episode/september2004/anorectal
Berberian J.G., & Burgess B.E. Tintinalli J.E., & Ma O, & Yealy D.M., & Meckler G.D., & Stapczynski J, & Cline D.M., & Thomas S.H.(Eds.), “Anorectal disorders,” in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9e, McGraw Hill, 2020. [Online]. Available: https://accessmedicine-mhmedical-com.ezproxy.library.dal.ca/content.aspx?bookid=2353&sectionid=219642697
Streitz Matthew, Long Brit, “Anorectal Disease,” in CorePendium, Burbank, CA: CorePendium, LLC, 2022. [Online]. Available: https://www.emrap.org/corependium/chapter/reclLjrt5HvPGSIDv/Anorectal-Disease#h.d78nqbylr3x
Bleday, Ronald, Perianal and perirectal abscess. uptodate.com, 2022. [Online]. Available: https://www.uptodate.com/contents/perianal-and-perirectal-abscess
Cavanaugh, Megan and Ormon, Rob, “Anorectal Disorders.” [Online]. Available: https://www.emrap.org/episode/april2011/anorectal
Lipp, Chris, “Anorectal Disorders.” [Online]. Available: https://canadiem.org/crackcast-e096-anorectal-disorders/