An anal abscess is an infected cavity filled with pus near the anus or rectum.
An anal fistula (also called fistula-in-ano) is a small tunnel that tracks from an opening inside the anal canal to an outside opening in the skin near the anus. An anal fistula often results from a previous or current anal abscess. It is observed that 30-50% of people with perianal abscess get fistula subsequently. However, a fistula can also occur without an abscess.

Causes for Fistula

Small glands just inside the anus are part of normal anatomy. If the glands in the anus become clogged, this may result in an infection. When the infection is serious, this often leads to an abscess. Bacteria, faeces or foreign matter can also clog the anal glands and cause an abscess to form. Crohn’s disease, trauma and radiation can increase the risk of infections and fistulas.


Anal abscesses are classified by their location in relation to the structures comprising and surrounding the anus and rectum: perianal, ischioanal, intersphincteric and supralevator. The perianal area is the most frequent and the supralevator the least. If any of these particular types of abscess spreads partially circumferentially around the anus or the rectum, it is termed a horseshoe abscess.
Fistulas are classified by their relationship to parts of the anal sphincter complex (the muscles that allow us to control our stool). They are classified as intersphincteric, transsphincteric, suprasphincteric and extrasphincteric. The intersphincteric is the most common and the extrasphincteric is the least common. These classifications are important in helping the surgeon make treatment decisions.


A patient with an abscess may have pain, redness or swelling in the area around the anal area or canal. Patients with fistulas have similar symptoms, as well as drainage from an opening near the anus. A fistula is suspected if these symptoms tend to keep coming back in the same area every few weeks.


Most anal abscesses or fistulas are diagnosed and managed based on clinical findings. Imaging studies like Endo Anal Ultrasonography or MRI can help in the diagnosis and management of deeper abscesses and may be used to visualize the fistula tunnel.


The treatment of an abscess is surgical drainage under most circumstances. Colorectal surgeons at Treat Piles Clinic are experts in this area. For most patients, an abscess can be drained surgically through a simple procedure. An incision is made in the skin near the anus to drain the infection.

Surgery is nearly always needed to treat an anal fistula. Antibiotics alone are not effective in treating abscesses or fistula. Antibiotics may be needed, in addition to surgery. We have a large series of patients diagnosed as fistula in ano and have been successfully treated by using Laser ablation of the tract on a daycare basis. We also have Fixcison device by which the complete tract is cored out and can be sent for histopathological evaluation to rule out inflammatory bowel disease or extra pulmonary tuberculosis.


Unfortunately, despite proper treatment and complete healing, an abscess or a fistula are known to recur [can come back]. If an abscess comes back, it suggests that perhaps there is a fistula that needs to be treated. If a fistula comes back, additional surgery will likely be required to treat the problem.

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