Anorectal Abscess & Fistula

• • Result from occlusion of anal glands and crypts at the dentate line

  • Occlusion may follow impaction of vegetable matter or edema from trauma

  • Abscesses are classified according to space they invade

  • -Supralevator

    -Ischiorectal

    -Superficial

    -Intersphincteric

    -Transphincteric

  • May also develop as a result of inflammatory bowel disease (Crohn)

  • Fistula-in-ano from the anus to the perianal skin develops when abscess cavity maintains persistent communication with the crypt

  • Goodsall rule: Used to identify direction of fistula tract

  • -Anterior external opening: Tract extends in a radial direction to the dentate line

    -Posterior external opening: Fistula tract curves to the posterior midline

Epidemiology

• • 10% of patients with Crohn disease have anorectal abscess fistulous disease with no prior history of inflammatory bowel disease

Symptoms and Signs

• • Severe anal/perianal pain, usually continuous and throbbing

  • Pain may worsen with movement and straining

  • Swelling and discharge may be noted

  • Patients may have fever, urinary retention

  • Severe, life-threatening perineal sepsis may develop

  • Patients with fistula-in-ano may have pain and bloody discharge

  • Exam findings may include tender perianal or rectal mass

  • Fistula: Internal and external openings with mucopurulent drainage

  • Fistulous tract is often palpable and firm

Laboratory Findings

• • May have elevated WBC count, especially with perineal sepsis

  • Drainage may have white blood cells, bacteria

Imaging Findings

• • Imaging studies are unnecessary in uncomplicated cases

  • Sinogram may reveal fistulous tract and branches

  • Transrectal US may reveal extent of sphincter involvement

  • CT scan may be helpful in identifying supralevator abscesses

• • Inflammatory bowel disease (Crohn disease)

  • Pilonidal disease

  • Hidradenitis suppurativa

  • Anal tuberculosis

  • Actinomycosis

  • Trauma

  • Anal fissure

  • Anal malignancy

  • Radiation injury

  • Chlamydiosis

  • Diverticulitis

  • Retrorectal tumors

Rule Out

• • Crohn disease

  • Anorectal malignancy

• • History and physical exam

  • -Is there history of diabetes or immunocompromised conditions, including medications (steroids, chemotherapy)?

  • Imaging studies are not indicated for uncomplicated cases

When to Admit

• • Abscesses should be drained; admission will depend on extent of abscess drainage required

  • Signs of perineal sepsis or complicated abscess

  • Fistula-in-ano by itself is not a surgical emergency

• • Treatment for abscess is surgical drainage

  • Intersphincteric abscesses are treated with internal sphincterotomy

  • Perianal and ischiorectal abscesses are drained through the perianal skin

  • Fistula-in-ano: Fistulotomy, currette tract and granulation tissue, heal by secondary intention

  • Fistula-in-ano: Involving external sphincter may be treated with seton placement or drainage with delayed repair with an endorectal advancement flap

Surgery

Indications

• • Anorectal abscesses require surgical drainage

  • Patients with diabetes or immunocompromised require urgent ...