Basics
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 pathogens:
- Associated diseases:
- Diabetes
- Inflammatory bowel disease
- Malignancy
- Immunocompromised host
Diagnosis
Signs and Symptoms
- Pain: Perianal, rectal, or pelvic
- Swelling, fluctuance, drainage, fever
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
- Constipation
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.
Diagnosis Tests & Interpretation
No labs or imaging routinely indicated
Lab
- CBC: Leukocytosis with left shift
- Wound culture: Not typically indicated
- Blood cultures: Mainly for sepsis
Imaging
- CT (with IV contrast, +/ " PO contrast)
- MRI (helpful with detecting fistulas)
- Endoanal US sometimes used
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
Treatment
Initial Stabilization/Therapy
Pain medication
Ed Treatment/Procedures
- Delayed drainage may worsen outcome
- Bedside drainage:
- Only if localized perianal abscess
- 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 deeper abscess
- Antibiotics rarely necessary:
- Extensive cellulitis
- Immunosuppression
- Valvular heart disease
- Systemic infection
- Prosthetic device
- PO:
- Amoxicillin clavulanate or fluoroquinolone
- Consider MRSA coverage
- IV:
- Cefoxitin
- Ampicillin sulbactam
- Combination therapy with ampicillin, gentamicin, and clindamycin or metronidazole
- Postoperative care:
- Sitz baths TID 24 hr after I&D
- High-fiber diet or bulking agent
- Analgesic
Medication
- Amoxicillin clavulanate: 875 mg PO q12h or 500 mg PO q8h
- Ampicillin sulbactam: 1.5 " 3 g IV q6h
- 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
Follow-Up
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
Followup Recommendations
Surgeon referral within 24 " 48 hr to evaluate for fistula:
- Fistulas develop in 25 " 50% of anorectal abscesses.
Pearls and Pitfalls
- Be certain of extent of abscess:
- Thorough rectal exam and probing is mandatory.
- Imaging adds insight into deeper areas not accessible to exam
- Deeper abscesses above dentate line have less pain and can present with isolated fever
Additional Reading
- Marcus RH, Stine RJ, Cohen, MA. Perirectal abscess. Ann Emerg Med. 1995;25(5):597 " 603.
- Rizzo JA, Naig AL, Johnson EK. Anorectal abscess and fistula-in-ano: Evidence-based management. Surg Clin North Am. 2010;90(1):45 " 68.
- Schubert MC, Sridhar S, Schade RR, et al. What every gastroenterologist needs to know about common anorectal disorders. World J Gastroenterol. 2009;15:3201 " 3209.
- Steele SR, Kumar R, Feingold DL, et al. Practice parameters for the treatment of perianal abscess and fistula-in-ano. Dis Colon Rectum. 2011;54:1465 " 1474.
See Also (Topic, Algorithm, Electronic Media Element)
- Abscess
- Anal Fissure
- Hemorrhoid
Codes
ICD9
- 565.1 Anal fistula
- 566 Abscess of anal and rectal regions
ICD10
- K61.0 Anal abscess
- K61.1 Rectal abscess
- K61.3 Ischiorectal abscess
- K60.4 Rectal fistula
SNOMED
- 91669008 Perirectal abscess (disorder)
- 36046008 Ischiorectal abscess (disorder)
- 82127005 perianal abscess (disorder)
- 235795007 Intersphincteric abscess (disorder)
- 197163002 Supralevator abscess (disorder)
- 286977005 Ischiorectal abscess/fistula (disorder)