Anal fistula

Background

• Inflammatory tract originating from infected anal gland connecting anal canal w/ skin
  • May be intersphincteric, suprasphincteric, transsphincteric, or extrasphincteric
• Goodsall's Rule
  • Draw imaginary line horizontally through the anal canal
    • If external opening is anterior to this line fistula runs directly into the canal
    • If external opening is posterior to this line fistula curves to post midline of canal
• Causes:
  • Perianal/ischiorectal abscess, Crohn, UC, malignancies, STI, fissures, FBs, TB

Clinical Features

• Fistulous tract open: Persistent, painless, blood-stained, mucous, malodorous discharge
• Fistulous tract blocked: Bouts of inflammation that are relieved by spontaneous rupture
• Abscess
  • Throbbing pain that is constant and worse w/ sitting, moving, defecation
  • May be only sign of fistula
• Fistulous opening
  • Adjacent to anal margin suggests superficial connection (e.g. intersphincteric region)
  • Distant from anal margin suggests deeper, more superior abscess

Diagnosis

• Endocavitary US w/ 3% hydrogen peroxide for definitive diagnosis

Management

1. Ill-appearing
   1. Analgesia
   2. IVF
   3. Anbx
   4. Urgent surgical consultation
2. Well-appearing
   1. Abx
      1. Ciprofloxacin 750mg PO BID AND metronidazole 500mg QID x7d
   2. Outpt sx referral
      1. Improperly excised fistulas may result in permanent fecal incontinence

Source

Tintinalli