An anal fistula is a small tunnel that forms between the inside of the anus and the skin around it. This tunnel usually develops because of an infection in an anal gland that causes a pocket of pus called an abscess. When the abscess drains, it leaves a passageway (fistula) connecting the infected area to the skin. If untreated, an anal fistula can cause pain, swelling, and discharge. It often requires medical treatment because the fistula does not heal on its own and can lead to recurrent infections.
Anal fistulas form when infection or injury leads to the creation of an abnormal tunnel between the anal canal and the skin. The main causes of anal fistula include:
When an anal gland becomes blocked, it creates an abscess (a pocket of infection). The pressure from the infection eventually forces the pus to drain through a new opening on the skin, forming a fistula.
Conditions like Crohn’s disease cause chronic inflammation of the bowel, weakening the tissues around the anus. This inflammation damages the tissue, which then heals abnormally, forming a fistula.
Injury to the anal area can cause tissue damage. If the area becomes infected, the body may form a tunnel between the anal canal and the skin, which results in a fistula.
If surgery in the anal or rectal area leads to infection, the healing process may result in fistula formation. The infection creates a path that connects the internal tissue with the skin.
Anal fistulas lead to several symptoms due to the abnormal tunnel connecting infected areas inside the body to the skin.
The ongoing infection and inflammation in the fistula irritate surrounding tissues, causing pain, especially during bowel movements or when pressure is applied.
The fistula acts as a passage for pus or blood from the internal infection to drain out through the skin, resulting in visible discharge.
The infection within the fistula triggers the body’s inflammatory response, causing swelling, redness, and tenderness around the area.
Because the fistula often does not heal on its own, it can trap bacteria, leading to repeated infections, which cause the abscess to refill, leading to more pain and discharge.
To diagnose an anal fistula, a colorectal surgeon will perform several evaluations to confirm the presence and extent of the fistula:
A colorectal surgeon visually inspects the area for any external openings, swelling, or signs of infection. This helps to identify if the fistula is close to the surface of the skin and the extent of the visible damage.
Gathering information about the patient’s symptoms, such as pain, discharge, or recurring infections, helps the surgeon determine whether the symptoms match the typical presentation of a fistula. A history of abscesses or past surgeries may also point to a fistula.
Imaging techniques such as MRI or endo-anal ultrasound aid in detecting deeper fistulas or those with complex branching that may not be visible externally. These scans provide a clearer map of the fistula’s path, helping the surgeon plan the best treatment approach, especially in more complicated cases.
For patients with anal fistulas, non-surgical treatments may be considered, particularly for simpler fistulas. Non-surgical treatments for anal fistulas focus on controlling infection and managing symptoms:
Antibiotics help control bacterial infections associated with fistulas, reducing inflammation, and pain, and preventing further complications. However, they do not close the fistula itself.
Surgical treatments are often necessary for more complex or persistent anal fistulas.
In this procedure, the surgeon opens the fistula from end to end, allowing it to heal as an open wound. It effectively eliminates the fistula and prevents recurrent infections. In some cases, there’s a risk of incontinence if the sphincter muscle is involved.
A seton, a surgical thread, is placed to allow the fistula to drain hence reducing infection. Seton placement reduces the risk of abscess formation and protects nearby muscles from damage. The healing process can take longer, and it may require multiple procedures.
For fistulas that involve the sphincter muscles, the surgeon may use tissue from a nearby area to cover the internal opening of the fistula. This procedure lowers the risk of incontinence and promotes healing without damaging the surrounding muscles.
This method is often used for treating complex or recurrent fistulas that pass through the anal sphincter muscles. The procedure involves creating an incision in the space between the inner and outer anal sphincter muscles, known as the intersphincteric space, to close off and sever the fistula tract.
Typically used for severe cases where other treatments have been unsuccessful or when the entire fistula tract needs to be removed. While this procedure removes the fistula, this procedure has a higher chance of affecting the anal sphincter muscles, which can lead to complications like incontinence. Due to these risks, fistulectomy is generally considered only when other options are not feasible.
A fistula plug is made from a biocompatible material that is inserted into the fistula tract to block it and allow surrounding tissues to heal around the plug. While it reduces the need for extensive surgery and supports recovery, there’s a chance the fistula may not fully close, requiring additional treatment.
It involves the use of a laser probe in the fistula tract and, through a combination of coagulation and shrinkage of the tract, results in progressive sealing of fistulas.
This is another sphincter preserving procedure that involves the use a video camera that can be inserted into the fistula tract that can be used to map out complex fistulas and treat them at the same time. Heated probes or brushes can be used to remove unhealthy tissue to promote healing.
Consult our MOH-accredited specialist for an accurate diagnosis & personalised treatment plan today.
Preventing the recurrence of anal fistulas involves maintaining good bowel habits and reducing the risk of infection. Adopting a high-fibre diet and staying hydrated can help prevent constipation, making bowel movements smoother and less straining. Regular physical activity promotes healthy digestion and reduces the likelihood of abscess formation. Keeping the anal area clean is also important to prevent infections that can lead to fistulas. In some cases, stool softeners may be recommended to ensure the healing process continues without complications.
MBBS (S’pore)|
M.Med (Surgery)|
MRCS (Ireland)|
FRCS (Edin)|
王健名医生
Dr. Calvin Ong is a Senior Consultant with more than 15 years of surgical experience. He specializes in colorectal and general surgery, performing minimally invasive as well as advanced robotic surgeries for benign and malignant colorectal conditions, including inflammatory bowel disease, pelvic floor disorders, colorectal cancer, and hernia repair. He is dedicated to providing high-quality, personalised care for his patients.
Dr. Ong graduated with a Bachelor’s degree in medicine and surgery from the National University of Singapore in 2008 and completed his Masters of Medicine (Surgery) at the same institute. He finished his advanced specialist training in 2016 and became a fellow of the Royal College of Surgeons of Edinburgh.
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Recovery time varies based on the complexity of the surgery. Most patients can return to normal activities within a few weeks, but full healing may take longer, especially for complex fistulas.
No, anal fistulas typically do not heal without medical intervention. If left untreated, they can lead to recurrent infections and abscesses.
Anal fistulas are very common and are more likely to occur in people with conditions such as Crohn’s disease or those with a history of anal infections.
Some discomfort is expected after surgery, but it is usually managed with prescribed pain relief. Minimally invasive techniques often result in less pain and may result in faster recovery.
Learn how surgical techniques for anal fistulas can alleviate persistent symptoms and provide long-term relief.
