Rectal Fistula

Aka: Rectal Fistula, Fistula-in-ano, Anorectal Fistula, Anal Fistula, Perianal fistula

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II. Causes

  1. Perirectal Abscess
    1. Fistula forms in 50% of cases
    2. Sequelae of rupture or surgery
  2. Anal Fissure
  3. Crohn's Disease
    1. Perianal fistula is most common fistula site
  4. Anal Cancer
  5. Tuberculosis
  6. Local Radiation Therapy
  7. Lymphogranuloma venereum
  8. Obstetric Trauma (e.g. fourth degree peroneal Laceration)

III. Types

  1. Simple Perianal fistula
    1. Single fistula tract distal to dentite line
  2. Complex Rectal Fistula criteria
    1. Anterior tract or
    2. Multiple tracts or
    3. Cross more than 50% of external anal sphincter or
    4. Recurrent
  3. Other colonic fistulas (more proximal, often related to Diverticular Disease)
    1. Colovesical fistula
    2. Colovaginal fistula

IV. Symptoms

  1. Chronic yellow, pustular (seropurulent) or mucus drainage from fistula
  2. Pain may be present at fistula tract

V. Signs

  1. Communicating tract between perianal skin and anus
  2. One or several external openings tracking toward anus
  3. Drainage may be spontaneous or with applying pressure with a finger from inside the anus

VI. Imaging

  1. MRI Pelvis with contrast enhancement
    1. Indicated in complicated Anal Fistulas
  2. CT Abdomen Pelvis with IV Contrast
    1. Indicated in more proximal fistulas (esp. colovesical or colovaginal fistulas)
  3. Endoscopic anorectal Ultrasound
    1. Consider in complicated Anal Fistulas

VII. Associated Conditions

  1. Perirectal Abscess

VIII. Management: Conservative Therapy

  1. Sitz baths
  2. High fiber diet
  3. Topical Analgesics
  4. Antibiotics
    1. Indicated when signs of infection
    2. Incision and Drainage of associated peri-anal abscess

IX. Management: Surgery (Fistulotomy)

  1. Indications
    1. Non-healing simple fistula
    2. Complex Anal Fistulas
    3. Increased risk factors for complications (e.g. Horseshoe Ischiorectal Abscess)
  2. Adverse effects
    1. Fecal Incontinence risk with complex Anal Fistula surgical repair
  3. Protocol
    1. Fistulotomy is typically delayed until after Perirectal Abscess heals
    2. Surgical repair requires precise mapping of the fistula tract
    3. Fistula tracts are mapped with exam under Anesthesia, as well as MRI and Ultrasound

X. Management: Refractory Complex Perianal fistulas In Crohn's Disease

  1. Consider initial Antibiotics
  2. Infliximab with or without Ciprofloxacin
  3. Surgical closure may be possible after initial treatment
    1. Refractory cases may improve with temporary fecal diversion
    2. Proctectomy with or without colectomy may be considered

XI. References

  1. Goroll (2000) Primary Care Medicine, Lippincott, p. 426
  2. Fargo (2012) Am Fam Physician 85(6): 624-30 [PubMed]
  3. Veauthier (2026) Am Fam Physician 114(2): 139-47 [PubMed]

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