An anal fistula, also called fistula-in-Ano, is a tunnel that develops between the internal part of anus and the skin surrounding it. The anus is the muscular opening at the end of the digestive system through which the waste is expelled from the body.
Anal fistulas are usually caused by infections that start in the anal glands. The infection could cause an abscess that either drains on its own or requires surgery in order to be drained from the skin around the anus. When this does drain, a permanent tunnel is created that connects the inflamed gland or anal canal with overlying skin.
Treatment for an anal fistula usually requires surgery, but there are rare occasions where it may be treated non-surgically.
Symptoms of an anal fistula –
Signs of an anal fistula may include:
- A visible opening on the skin around the anus
- An inflamed reddened area around the opening of the canal
- • Pus, blood, or stool draining from the channel
- Pain/discomfort in the anal and rectal area, especially when sitting or having a bowel movement
- Occasional fever
Causes
Most anal fistulas develop as a result of an infection that occurs in one of the anal glands. This infection forms an abscess that can either drain on its own or be surgically drained through the skin near the anus. This creates a fistula, a channel that forms under the skin, along the course of this drainage. It forms a passage from the infected anal gland or canal to a point on the outer skin around the anus.
The anal verge has notable layers of sphincter muscles which allow you to control bowel movement. They are also classified in relation to the sphincter muscles, and this is very important for surgeons when they assess them to plan appropriate treatment strategies.
Risk Factors for Anal Fistula
There are several factors that can make a person more likely to develop an anal fistula, such as:
- History of previous drainage of anal abscess
- Conditions such as Crohn’s disease, or related inflammatory bowel conditions
- Injury to the anal region
- Anal area infections
- Treatments for anal cancer that involve surgery or radiation
Anal fistulas occur more commonly in adults, especially in patients near their 40s but can also affect younger patients with a history of Crohn’s disease. If I notice, they are more common in males than females.
Complications
Even after appropriate treatment of an anal fistula, there is always the risk of recurrence of an abscess or new anal fistulas. Surgical operations can also cause side effects including faecal incontinence (the inability to retain stool).
Diagnosis
To diagnose an anal fistula, your health care provider will ask about your symptoms and examine you. This may include a visual inspection of the area around and inside the anus.
Though the external opening of an anal fistula is normally apparent on the skin around the anus, the internal opening in the anal canal is more difficult to find. To effectively treat an anal fistula, you need to understand the entire anatomy.
To visualize the fistula tunnel, one or more of the following imaging modalities may be used:
Pelvic MRI: This imaging technique provides detailed images of the fistula tract and the adjacent tissues, such as the sphincter muscle and the pelvic floor.
Endoscopic Ultrasound (Endoanal Ultrasound): This test uses high frequency ultrasound waves to look at the fistula, sphincter muscles and surrounding tissues.
Fistulography — an x-ray procedure in which a contrast agent is injected into the anal fistula tunnel.
EUA (Examination Under Anaesthesia): A colon and rectal surgeon may recommend an EUA to obtain a full view of the fistula tunnel and to check for other complications, if any.
Another way to find the internal opening of the fistula is:
Fistula Probe: has a narrow, circular, flexible structure that can range from 10 cm to 50 cm long, is inserted through the fistula tunnel to help identify the structure.
Anoscope: A small endoscope that can be used to inspect the anal canal.
Colonoscopy or Flexible Sigmoidoscopy: These are the procedures where an endoscope is utilized to assess some or all of the large intestine. Sigmoidoscopy looks at the lower segment (sigmoid colon), and colonoscopy examines the whole length, which is especially important if you suspect conditions like ulcerative colitis or Crohn’s disease.
Direct Dye Solution Injection: This might help to identify the fistula orifice.
Treatment-
Management of anal fistula depends on the fistula site, complexity, and aetiology. The main goals are to obliterate the fistula so it doesn’t return, and to preserve the sphincter muscles (which, when damaged, lead to faecal incontinence). Surgical intervention will often be required, but there can be cases when the non-surgical approach may be possible too.
Options for surgical treatment: –
1.Fistulotomy: The surgeon makes an incision at the fistula’s internal opening, removes any infected tissue, and flattens the fistula tunnel and stitches it in the open position. In more complex cases of fistulas, the remaining parts of the tunnel may also have to be surgically removed. In the case where a large portion of the sphincter muscle is involved, or if the whole tunnel is not identifiable, the fistulotomy can be done in two procedures.
2.Endorectal advancement flap: In this type of surgery, the doctor will form a flap with the rectal wall and remove the internal opening of the fistula. The flap is then used to overlay the closure, allowing for less of the sphincter to be cut.
3.Ligation of the intersphincteric fistula tract (LIFT): This two-step process has been devised for more complex or extensive fistulas. LIFT gives the surgeon access to the fistula between the sphincter muscles without having to cut them. The first step is placement of a silk or latex string (seton) into the tunnel, allowing for gradual widening over time. Weeks later, the surgeon cuts out the inflamed tissue and seals the inner opening of the fistula.
Non-Surgical Treatments-
1.Placement of a seton: A surgeon puts a seton (a piece of string or material) through the fistula so that it helps to drain any infection and help heal the tunnel. If required, this technique may be supplemented with surgical intervention.
2. Fibrin glue and collagen plug, the surgeon prepares the fistula by clearing the tunnel and suturing the internal opening. A specialized glue, made from fibrin—the protein responsible for blood clotting—is injected through the external opening, or a collagen plug can seal the anal fistula’s tunnel before closing.
3.Medications: If the anal fistula is related to Crohn’s disease, medications are critical to successfully treating it.
In patients with complex anal fistulas, more invasive surgical alternatives may be necessary and/or preferable, including:
4.Stoma (Colostomy/Ileostomy): This type redirects the intestines into a temporary opening created in the abdominal wall to divert waste away from the anal canal. This gives the damaged area some time to heal.
5.Muscle flap: For more complicated cases, the surgeon may fill the fistula tunnel with healthy muscle tissue taken from the thigh, labia, or buttock in order to facilitate healing.
