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

Differential Diagnosis

Anorectal Disorders

• Anal fissure
• Anal fistula
• Anal malignancy
• Anal tags
• Anorectal abscess
• Coccydynia
• Colorectal malignancy
• Condyloma acuminata
• Constipation
• Crohn's disease
• Cryptitis
• GC/Chlamydia
• Fecal impaction
• Hemorrhoids
  • Internal hemorrhoid
  • External hemorrhoid
• Levator ani syndrome
• Pedunculated polyp
• Pilonidal cyst
• Proctalgia fugax
• Proctitis
• Pruritus ani
  • Enterobius (pinworms)
• Rectal foreign body
• Rectal prolapse
• Syphilitic fissure

Non-GI Look-a-Likes

• Prostatitis

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
   3. Spasm treatment
      1. Nitroglycerin, Lidocaine
      2. Sitz baths

See Also

Anorectal Disorders

Source

Tintinalli