Anal Fistulas and Abscesses

Anal fistulas and anal abscess
What are Anal Fistulas and Abscesses
By Dr. Tan Wah Siew
An anal abscess is a collection of pus that forms under the skin around the anus.

This is usually caused by an infection of a gland inside the anal canal. An anal fistula may develop as a result of a previous perianal abscess. A tunnel develops causing an abnormal connection between the perianal skin and the anal canal.

An anal abscess is best treated with surgical drainage. A cut is made in the skin over the anal abscess to drain the pus. This is usually performed under general or regional anaesthesia.

An anal fistula rarely closes spontaneously. As such, surgery is usually required. The majority of anal fistulas are cryptogenic in origin. Most of these fistulas are simple fistulas, although complex fistulas in which there are multiple tracts and/or involves a large amount of anal sphincter muscles can also be encountered. A minority of anal fistulas may be associated with Crohn’s Disease.

There are many surgical options available but the surgery best suited depends on the anatomy and complexity of the fistula and should be discussed with your colorectal surgeon.

The surgical options include:

  • Fistulotomy (cutting open the fistula tract)
  • Tight seton insertion (using a tight string to cut through the sphincters slowly to decrease the risk of damage to the anal sphincters)
  • Loose seton insertion (using a soft rubber string to prevent abscess formation)
  • Ligation of intersphincteric fistula tract (dividing the fistula tract with an incision made between the anal sphincters, to minimise damage to the sphincters)
  • Rectal advancement flap (pulling down the inner lining of the rectum to close the internal opening of the anal fistula)
  • Video assisted anal fistula treatment (VAAFT) This method uses a video fistuloscope to locate the internal opening of the fistula in the anal canal followed by destruction of the fistula from the inside, cleansing of the fistula tract and finally closure of the internal opening.
  • Defunctioning colostomy (diverting stools away from the anus to prevent infection in the fistula) This is usually not considered until most of the other methods have failed to treat the anal fistula.
Colon Cancer Surgeon - Dr Tan Wah Siew
Dr Tan Wah Siew

Senior Consultant Colorectal Surgeon

MBBS, MMed (Surgery), FAMS, FRCSEd

Dr Tan Wah Siew was senior consultant surgeon at the Department of Colorectal Surgery, Singapore General Hospital (SGH) prior to her move to private practice. She was the first female consultant colorectal surgeon in the history of SGH, and was one of the earliest female surgeons in Singapore to be trained in robotic colorectal surgery.

She graduated from the Faculty of Medicine, National University of Singapore in 2003 and completed her Advanced Surgical Training in General and Colorectal Surgery at SGH in 2011. In 2013, she completed a one year Ministry of Health sponsored Healthcare Manpower Development Plan Fellowship (HMDP) at St. James University Hospital in Leeds, United Kingdom. While there, she trained in minimally invasive and robotic colorectal surgery for colorectal cancer, surgery for inflammatory bowel disease as well as treatment of locally advanced rectal cancers and recurrent pelvic cancers requiring removal of multiple organs and/or pelvic exenterations.

Singapore Colon Surgeon
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