Page 178 - Medicine and Surgery

P1: KOA
BLUK007-04 BLUK007-Kendall May 25, 2005 7:57 Char Count= 0

174 Chapter 4: Gastrointestinal system

Complications Clinical features
Infections may form a perianal abscess. Patients often present with an abscess, the incision of
which completes the fistula. Patients with a completed
Management fistula present with a discharging sinus that causes lo-
Primaryanalfissuresmayhealspontaneously.Refractory calised pruritus and excoriation.
fissures may require surgical management. An incision is
made into the perianal skin on one side of the anal canal Investigations
and the internal sphincter is divided without entering Proctoscopy may reveal the internal opening with a flexi-
the lumen. ble probe used to demonstrate the track. Sigmoidoscopy
is required to exclude associated rectal diseases.

Fistula-in-ano
Management
Definition Primary fistulas are laid open to granulate and epithe-
A fistula is an abnormal communication between one lialise. In pelvirectal fistulas such an incision would di-
epithelial surface and another. A fistula-in-ano connects vide the anorectal ring causing incontinence. These and
the anal canal to the perianal skin. secondary fistulae are treated conservatively.

Aetiology Pilonidal sinus
Most anal fistulae have no obvious cause. Associations
include inflammatory bowel disease, tuberculosis and Definition
carcinoma of the rectum. A sinus of the natal cleft containing hair that often be-
1 Low anal fistula is the commonest form with a com- comes infected.
munication from the anal canal below the level of the
anal crypts to the perianal skin.
Aetiology/pathophysiology
2 High anal fistulas have a track which extends above
It is thought that sinuses arise from penetration of hairs
the pectinate line below the anorectal ring. The mus-
subcutaneously with secondary infection. A post anal
cle fibres of the internal and external anal sphincter
pilonidal sinus typically occurs around 2 cm posterior
surround the rectum. In both low and high fistulas
to the anus and extends superiorly and subcutaneously
the track of the fistula may pass through the fibres
for about 2–5 cm.
of both sphincters or descend in the intersphincteric
space.
3 Anorectal fistula Clinical features
Pelvirectal fistula is a direct communication be-
The sinus only becomes symptomatic when infection
causes an abscess with swelling, tenderness and dis-
tween the rectum and the skin bypassing the
charge.
anal canal and passing through the levator ani
muscle.
Ischiorectalfistulaissimilartoalowfistula,butwith Management

additional extension upwards towards the rectum Abscesses are drained, de-roofed and cleaned under gen-
without penetrating the levator ani muscle. eral anaesthetic. The cavity is left open to granulate. Pi-
lonidal sinuses tend to recur.
Pathophysiology
Goodsall’s rule states that if the fistula lies in the anterior Anorectal abscess
half of the anal area then it opens directly into the anal
canal, while if a fistula lies in the posterior half of the Definition
canal then it tracks around the anus laterally and opens Anorectal abscesses may occur as perianal, ischiorectal
into the midline posteriorly. or high muscular abscess.