Courtesy of THIS Quarterly magazine  
 
 
Anal Fistula  
 
   
     
 

AN ANAL FISTULA IS AN ABNORMAL TUNNEL that develops between the anal canal and its surrounding skin. It is not a new disease, Hippocrates, the Father of Medicine was treating this condition 2500 years ago. It is not an uncommon ailment, affecting 0.01% to 0.03% of the population, usually between 20 to 40 years of age. It is twice as common in men, and in smokers.

The commonest cause is an infection of one of the tiny glands located around the mid-level of the anal canal. Pus from the infection tracts down to the skin creating a boil or abscess which bursts through the skin surface to form a fistula. When it takes a direct route to the skin, a simple fistula is formed, but when it takes a circuitous route with detours, a complex fistula with secondary tract(s) or internal abscess results. Leakage of faeces and bacteria from the anus through the internal opening prevents healing of the fistula. In healthy individuals, infection around the anus is uncomfortable and painful but not serious but in people with impaired immunity (HIV AIDS, leukaemia, diabetes, or on chemotherapy or steroids) such infection can be very dangerous. Rare causes of fistula include Crohn’s disease (Inflammatory Bowel Disease), tuberculosis and trauma.

The main symptom of a fistula is recurrent discharge of blood and pus from a tiny hole around the anal opening. It usually started as a boil or pimple that did not respond to antibiotics. Some patients present with recurrence after surgery. An anal fistula can only be cured when the opening inside the anus is closed and all the tracts and internal abscesses present are cleared and drained. This can be achieved by using a seton, a string that loops through the whole length of the fistula, as documentated by Hippocrates; a medicated thread (Kshar Sutra) which is widely used in India; a fistula plug or glue. These techniques aim to reduce leakage from the internal opening, to clear the tract of debris and pus and to stimulate rapid cell growth to heal the fistula. Unfortunately, they have low success rate but as they do not require cutting, the risk of incontinence is low.

The most common and effective method is to lay-open (or cut-open) the fistula tract and internal opening surgically.

 

This method has a high success rate but the disadvantage is that it creates an open wound which may be large, and there is a risk of incontinence if the internal opening is located too high up in the anal canal.

In the last few years, three new methods of closing the internal opening have been introduced. Mucosal Advancement Flap involves the suturing of the internal opening and covering of the suture line with surrounding mucosa to prevent infection and failure, LIFT operation (Ligation of Intersphincteric Fistula Tract), pioneered by Professor Arun Rojanasakul of Thailand, involves the disconnection of the fistula in between the anal sphincter muscles, and Surgical Stapling, first introduced in Spain. These three techniques do not cut the sphincter muscles, so there is no risk of incontinence but technically they are difficult to perform and wound infection is a problem.

In the past, surgeons only have metal probes to define the correct anatomy of a fistula tract and to detect the presence of secondary tracts or internal abscesses. The accuracy and ultimate success of treatment very much depend on the skill and experience of the surgeon. Today it is possible to visualise the anatomy of a fistula and form a “road map” by using MRI (magnetic resonance imaging), 3-D anorectal ultrasound and video assisted anal fistuloscope. The accuracy of visualisation is dependent on the local expertise available for each technique but is vital for good surgical outcome.

The nature and complexity of anal fistula is different for each patient, ranging from the very simple to the highly complicated with history of multiple failed operations. There is no single operation that can cure all. Colorectal surgeons are now well equipped with all the necessary diagnostic tools and surgical options to offer the most appropriate treatment for each patient, based on a mutually agreed balance of best success rate, lowest risk of incontinence, fastest recovery and cheapest financial cost.

 
 
 
DR GOH HAK SU | Colorectal Surgeon
MBBS, FRCS, FAMS

Address
 
Goh Hak-Su Colon & Rectal Centre
6 Napier Road #04-08
Gleneagles Medical Centre
Tel : (65) 6473 0408
Website : www.gohhaksu.sg