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Anorectal Sepsis – Part 2

Clinical Features

Perianal abscess (Fig. 27 A) causes pain, erythema and swelling in the anorectal region, or buttock (ischiorectal abscess – Fig. 27 B).

Fig. 27 A-B: Anal margin abscess (left) and ischiorectal abscess (right).

Deep-seated anal pain may occur in the presence of intersphincteric abscess. When the diagnosis is unclear , an EUA may be necessary (Fig. 28)

Fig. 28 : Rectal extension of intersphincteric abscess.

Management of Abscess

The mainstay of treatment is the prompt drainage of the pus for any abscess(Fig. 29)


Fig. 29: Drainage of the pus in a ischiorectal abscess.

Abscesses secondary to anorectal Crohn’s disease are often chronic and may require prolonged drainage and antibiotic therapy.

The horseshoe abscess (Fig. 30) is usually due to posterior anal space abscess with bilateral ischiorectal extensions or to ischiorectal abscess extending to the controlateral space across the post-anal space.

Fig. 30: Endosonography (A)  of posterior horseshoe abscess (B).

Management of Fistula

Several surgical options exist for the treatment of anal fistula, and management must be individualized evaluating the sex of the patient, the amount of external sphincter that track encompasses, the location (anterior or posterior). The most common treatment is fistulotomy, consisting of unroofing the fistula tract from the internal to external opening and then allowing the wound to heal by secondary intent (Fig. 31 A-B).

Fig. 31 A-B: One-stage fistulectomy.

An intermediate approach to this problem is a two step fistulotomy, wich involves cutting all the non-sphincteric soft tissue with internal anal sphincter, and then placing a latex vessel loop around the remaining skeletal component of the external sphincter (Fig. 32 A-B)

Fig 32 A-B.: Two stages fistulotomy: latex vessel placed around the external sphincter.

The loop is left in place until the wound heals around it, creating a shortened fistula tract involving only external sphincter muscle (Fig. 33). 

Fig. 33: Site of fistula track is replaced by fibrosis and wound healing.

As the muscle is transected , local fibrosis ensures that separation of the muscles ends is not as wide as the separation after one-stage fistulotomy. This theoretical advantage has not been confirmed by endosonographic studies.

The risk of incontinence increase when fistulotomy is performed for high level transphincteric fistula (> 1/3 to 1/2   of the external sphincter). This is especially so when fistulas are in an anterior position or in females.


The management of the majority of abscess and fistulas involving the anal region is relatively straightforward. Acute abscesses should be immediately drained and there is no need of antibiotics in uncomplicated cases. A safe option for complicated anal fistulas is draining with a latex loop ,evaluating a two steps traitment. Patients with Crohn’s disease, diverticulitis, history of known or suspected malignancy may warrant further imaging before operation.

1) Parks AG, Gordon PH, Hardcastle JD 

A classification of fistula in ano

Br J Surg 1976 ; 63 : 1-12

2) Marti M.C., Givel I.C.

Surgery of Anorectal Diseases


3) Stelzner F.

Die Anorectalen Fisteln


4) Gizzi G.

Argomenti di Proctologia

Minerva Medica