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
  4. Anorectal cancer
  5. Tuberculosis
  6. Local Radiation Therapy
  7. Lymphogranuloma venereum
  8. Obstetric Trauma (e.g. fourth degree peroneal Laceration)

III. Types

  1. Simple Rectal Fistula
  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

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 (indicated in complicated Anal Fistulas)

VII. Associated Conditions

VIII. Management: Conservative Therapy

  1. Sitz baths
  2. High fiber diet
  3. Topical Analgesics

IX. Management: Surgery (Fistulotomy)

  1. Indications
    1. Non-healing 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. References

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

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