Anorectal Fistula

ANORECTAL FISTULA (FISTULA IN ANO) Definition:  Fistula is an abnormal passage from one epithelial surface 

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to another epithelial surface It is a tube like tract with one opening in the anal canal and the other usually in the perianal skin. It is an inflammatory track with one opening in the anal canal and another in perianal skin Fistulas occur spontaneously or secondary to perirectal abscess. Most fistulas originate in the anal crypts at the anorectal juncture

Goodsall's rule  If external opening is anterior to an imaginary line drawn

horizontally through anal canal, fistula usually runs directly into anal canal  If external opening is posterior to line, the fistula usually curves to posterior midline of anal canal  In children, track is usually straight Classification 1. 2. 3. 4.

Intersphincteric Transsphincteric Suprasphincteric Extrasphincteric

Etiology:  Erosion of anal canal  Extension from infection from a tear in lining in anal canal  Infecting organism is commonly Escherichia coli  Fistulas usually arise spontaneously or occur secondary to drainage of a perirectal abscess.  Predisposing causes include Crohn's disease and TB.

 Most fistulas originate in the anorectal crypts; others may result from diverticulitis, tumors, or trauma.  Fistulas in infants are congenital and are more common in boys.  Rectovaginal fistulas may be secondary to Crohn's disease, obstetric injuries, radiotherapy, or malignancy. Risk factors:  Injection of internal hemorrhoids, puncture wound from eggshells or fish bones, foreign objects, enema tip injuries  Ruptured anal hematoma  Prolapsed internal hemorrhoid  Acute appendicitis, salpingitis, diverticulitis  Inflammatory bowel disease (chronic ulcerative colitis, Crohn disease)  Previous perirectal abscess  Radiation treatment to perineum/pelvis Signs and symptoms:      

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Constant or intermittent drainage or discharge Firm tender perianal lump External anal sphincter pain during and after defecation Spasm of external anal sphincter during and after defecation Anal bleeding Discoloration of skin surrounding the fistula Fistulous opening frequently granulose or scarred Possible fever A fistula is suggested by the presence of a small external opening outside the anal verge draining mucus, pus, or fecal matter. A fistula is confirmed by the demonstration of an internal opening within the anal canal. A history of recurrent abscess followed by intermittent or constant discharge is usual.

 On inspection, one or more secondary openings can be

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seen, and a cordlike tract can often be palpated A probe inserted into the tract can determine the depth and direction, and anoscopy with probing may reveal the primary opening. Sigmoidoscopy should follow. Hidradenitis suppurativa, pilonidal sinus, dermal suppurative sinuses, and urethroperineal fistulas must be differentiated from cryptogenic fistulas Fistulas are associated with purulent discharge that may lead to itching, tenderness, and pain.

Diagnostic procedures:  Proctoscopy  Sigmoidoscopy  Probe inserted into tract to determine its course  Injection of dilute methylene blue into abscess cavity may be helpful in demonstrating fistula Differential diagnosis  Pilonidal sinus  Perianal abscess  Urethroperineal fistulas  Ischiorectal abscess  Submucous or high muscular abscess  Pelvirectal abscess (rare)  Rule out: Crohn disease; carcinoma; retrorectal tumors Treatment  Fistulotomy - surgical incision of entire length of fistula

(unroofing). Mucosal tract may be cauterized or curetted. Sphincterotomy.  Fistulectomy - complete excision of tract (rarely indicated due to extensive tissue loss). Sphincterotomy.

 General anesthesia or regional anesthesia usually required  Postoperative - hot sitz baths  Avoid constipation  Treatment is by surgical incision or excision under anesthesia.  Care must be taken to preserve the anal sphincters.  The only effective treatment is surgery.  The primary opening and the entire tract are unroofed and converted into a "ditch."  Partial division of the sphincters may be necessary.  Some degree of incontinence may occur if a considerable portion of the sphincteric ring is divided.  Because of delayed wound healing, fistulotomy is inadvisable in the presence of diarrhea, active ulcerative colitis, or Crohn's disease.  Metronidazole or other appropriate antibiotics can be given to Crohn's disease patients with symptomatic anorectal fistulas