Anal fistula and peri-anal abscesses

Peri-anal abscess is the term given to an abscess, of any cause, that occurs around the anus. In general, all abscesses require surgical drainage to allow the infection to be treated properly.

An anal fistula is a tract, or tunnel, between the bowel (anal canal) and the skin. A fistula usually causes one or more of the following symptoms

  • Discharge
  • Pain
  • Recurrent abscesses
An anal fistula (fistula in ano) usually follows a peri-anal abscess, but may also ariseĀ de novo.

The majority of fistulae are either deliberately created by a doctor to allow drainage of infections (for the treatment of a peri-anal abscess) or crypto glandular (arising from infected anal glands). Other rarer causes for fistula need to be excluded at the time of surgery either clinically or with biopsies (histologically).

At the time of surgery the fistula is examined for critical features which will determine management, such as

  • Internal opening of the fistula
  • Length of the tract
  • Whether there are multiple tracts or a single tract
  • Relationship of the internal anal sphincter (IAS) and external anal sphincter (EAS) to the tract

The relationship of the fistula to the IAS and the EAS is the most important factor for clinical management as it decides what operation can be safely offered to you.

All fistula operations have a balance between cure, recurrence and incontinence. It is important that you understand the relative risks of each of these factors for any operation you are offered.

 

Fistulotomy

This is referred to as ‘laying open’ the fistula, and is the simplest operation to perform. It is essentially converting the ‘tunnel’ of a fistula into a ‘gutter’, to allow the fistula to heal and to obliterate the previous tract. Wherever possible, it is the operation of choice because it gives the best chance of curing the fistula.

However, this operation is not suitable for all fistula, as in some cases, the surgeon may need to cut into the IAS resulting in too high a risk of incontinence. A fistulotomy is not suitable for complex fistula.

A fistula may be deemed complex for many reason, but it essentially means that if a fistulotomy was performed on the fistula, an unacceptably high rate of incontinence would ensue.

 

Seton

A seton is the term given to a loose rubber-band type drain that surgeons use to treat fistulae. It is placed along the fistula tract and allows the fistula to drain freely. It is the treatment of choice for an acute fistula as it allows the infection to settle down and permits the tract to become more mature, or fibrous.

A seton is also the treatment of choice for fistulae that cross either the IAS or the EAS as placing a seton does not cause any damage to the sphincter muscle.

Setons generally need to be inserted and removed while under anaesthesia, so that a complete assessment of the fistula tract can be completed without undue discomfort.

In around 40% of patients, the seton itself will cure the fistula. In most situations however, the seton acts as a bridge to a second stage procedure; either a mucosal advancement flap or a LIFT procedure.

 

Mucosal advancement flap

This is a significantly more complex operation than the two previous ones. In this operation, a flap or wedge of tissue from inside the anus is pulled down and sutured in place to cover the internal opening of the fistula (ie inside the anus). The old fistula tract that leads away from the bowel is then cleaned out, so as to try and prevent the infection from recurring.

The true utility of mucosal advancement flaps is that they can be used for complex fistulae.

The recurrence rate is relatively high (around 30 to 40%) but there is little effect on continence (<15%), even with repeat operations.

 

LIFT procedure

The LIFT (ligation of inter-sphincteric fistula tract) procedure is a relatively new procedure for the treatment of fistulae. It consists of ligating or tying off the fistula tract between the IAS and the EAS to remove the source of ongoing infection. It offers a better balance of cure/recurrence/incontinence than older procedures for complex fistulae.

It has become my treatment of choice for complex fistulae for of a number of reasons:

  • Low incontince rates
  • Low recurrence rates
  • More robust operation than mucosal advancement flap

The LIFT procedure can be used for recurrent fistulae. It is performed as a day procedure and does not require require any bowel preparation prior to the operation.