Author:
James A.Nelson
Scott A.Miller
Description
Localized infection and accumulation of purulent material adjacent to anus or rectum
Etiology
- Anal crypt gland infection, with spread to adjacent areas separated by muscle and fascia:
- Perianal:
- Most common
- Usually with red bulge near anus
- Ischiorectal:
- Large potential space
- May become very large before diagnosed
- Can communicate posteriorly with other side forming “horseshoe” abscess
- Intersphincteric:
- Contained at primary site of origin between internal and external sphincters
- Supralevator:
- Very deep above levator ani
- Needs operative debridement under general anesthesia
- Often systemic symptoms before diagnosis is made
- Bacterial cause is typically a mix of stool species
History
- Perianal pain:
- Aggravated by defecation, sitting, coughing
- Dull deep pelvic or rectal pain:
- Less pain if arises above dentate line (ischiorectal and supralevator)
- Rectal or perirectal drainage
- Fever/chills
Physical Exam
- Perianal swelling, erythema, induration, fluctuance, tenderness
- Inner cleft buttock abscess = red flag
- Rectal abscess can track out to buttock
- Rectal exam is the most important diagnostic intervention
- Rectal swelling or tenderness
- Fistula can be probed, or palpated as a cord
Essential Workup
- Careful history and physical exam with rectal exam are paramount in making diagnosis
- Have high index of suspicion for any constant perirectal pain
Diagnostic Tests & Interpretation
No labs or imaging routinely indicated
Lab
- CBC: Leukocytosis with left shift
- Wound or blood culture: Not typically indicated
Imaging
- CT (with IV contrast, +/- PO contrast)
- MRI (helpful with detecting fistulas)
- Endoanal US sometimes used by emergency physicians
Diagnostic Procedures/Surgery
Incision and drainage (I&D) is the definitive management
Differential Diagnosis
- Anal fissure
- Sentinel pile in the posterior midline or anterior midline
- Thrombosed or inflamed hemorrhoids
- Anal ulcer (i.e., HIV)
- Proctitis (i.e., gonococcal)
- Anorectal carcinoma
Initial Stabilization/Therapy
Pain medication
ED Treatment/Procedures
- Delayed drainage may worsen outcome
- Bedside drainage:
- Generally ED physicians drain perianal abscess but if the rectum is involved, the general surgeon does the drainage
- Probe to rule out deeper tract
- Radial incision close to anal verge
- Explore cavity, breaking any loculations
- Irrigate liberally
- Loose packing removed at 48 hr
- Operative debridement under general anesthesia:
- If local anesthesia is inadequate, or if rectal involvement
- Antibiotics rarely necessary unless:
- Postoperative care:
- Sitz baths t.i.d 24 hr after I&D
- High-fiber diet or bulking agent
- Analgesic
Medication
- Amoxicillin-clavulanate: 875 mg PO q12h or 500 mg PO q8h
- Cefoxitin: 1-2 g IV q6-8h
- Clindamycin: 600-900 mg IV div q8h
- Gentamicin: 3-6 mg/kg/d IV div q8h
- Metronidazole: 7.5 mg/kg IV q6h
Disposition
Admission Criteria
- Need for operative drainage
- Systemic toxicity/signs of sepsis
Discharge Criteria
Adequate I&D with complete drainage
Issues for Referral
All should be referred to surgeon in 24-48 hr
Follow-up Recommendations
Surgeon referral within 24-48 hr to evaluate for fistula:
- Lorenzo-RiveroS. Drainage of perirectal abscess. In: HoballahJ, Scott-ConnerC, ChongH (eds). Operative Dictations in General and Vascular Surgery. Springer; 2017.
- RizzoJA, NaigAL, JohnsonEK. Anorectal abscess and fistula-in-ano: Evidence-based management . Surg Clin North Am. 2010;90(1):45-68.
- SchubertMC, SridharS, SchadeRR, et al. What every gastroenterologist needs to know about common anorectal disorders . World J Gastroenterol. 2009;15:3201-3209.
- SteeleSR, KumarR, FeingoldDL, et al. Practice parameters for the treatment of perianal abscess and fistula-in-ano . Dis Colon Rectum. 2011;54:1465-1474.
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