Brief overview
- What is an anal fistula? Connecting passage between the last section of the intestine (anal canal) and the outer skin in the area of the anus.
- Causes: An anal fistula often develops in connection with an accumulation of pus in the anal area (anal abscess), but it can also occur on its own. Certain diseases such as chronic inflammatory bowel disease, diabetes mellitus, immunodeficiency (e.g. HIV), blood disorders and lifestyle habits (e.g. smoking, prolonged sitting) can increase the risk of anal fistula.
- Treatment: An anal fistula does not heal by itself or by taking medication alone. Treatment consists of surgery and subsequent wound care.
- Symptoms: Oozing, purulent or stool-containing secretions, pain (during bowel movements, when sitting), swelling and/or itching in the anal area, possibly non-specific symptoms such as fever, tiredness, fatigue
- Diagnostics: Examination of the external anal region (visible mouth of the anal fistula on the bottom), palpation, probing of the fistula tract, possibly endoscopy of the rectum (proctoscopy) or colonoscopy to exclude concomitant diseases (e.g. polyps, diverticula, tumors), possibly ultrasound examination of the rectum
What is an anal fistula?
In an anal fistula, a connecting duct forms between the (inner) mucous membrane of the anal canal and the surrounding (outer) skin of the anus. Anal fistulas are often caused by inflammatory changes in the area of the rectum, for example due to accumulations of pus (anal abscesses).
Some anal fistulas are open, others end blindly. The fistula opening is either located on the outer skin and ends blindly on the inside or the opening lies in the intestinal mucosa without the fistula channel reaching the outer skin.
Anal fistulas are located differently:
- Within the skin and under the sphincter muscles (subanodermal)
- Between the internal and external sphincter (intrasphincteric)
- Course through both sphincters (transsphincteric)
- Beginning directly above the sphincter and opening in the anal region (suprasphincteric)
- Beginning further inside the anal canal without close proximity to the sphincter (extrasphincteric)
Most common are intrasphincteric anal fistulas, which run between the two sphincters, and transsphincteric anal fistulas, which run through both the internal and external sphincter.
Frequency
Where does an anal fistula come from?
An anal fistula on the buttocks most frequently occurs in connection with an accumulation of pus in the anal area (anal abscess). An anal abscess, in turn, is often caused by inflammation of the so-called proctodeal glands. These small, rudimentary glands are located in the anus between the external and internal sphincter muscles. Their excretory duct opens into the anal canal. Men usually have more proctodeal glands than women.
There are various diseases and factors that increase the risk of an anal abscess and associated anal fistula, for example:
- Chronic inflammatory bowel disease, e.g. Crohn’s disease, ulcerative colitis
- Diabetes mellitus
- Diseases of the hematopoietic system (e.g. leukemia)
- Diseases associated with immunodeficiency (HIV infection)
- smoking
- Obesity (adiposity)
- Predominantly sedentary work
- Prolonged sitting (pushing) during bowel movements
Anal fistula – what to do?
If there is an anal abscess, the doctor opens the accumulation of pus in a surgical procedure. This drains the pus. What remains is a wound cavity, which is carefully rinsed with a disinfectant solution. The wound remains open after the operation (i.e. it is not stitched up) and is filled with gauze tamponade. Good wound care is required afterwards.
There are various surgical techniques for treating anal fistulas. The type of operation depends on the course of the fistula in the tissue.
In very rare and severe cases of anal fistula, it is necessary to temporarily create an artificial anus. This involves the surgeon connecting the end of the bowel to the outer skin on the abdomen. In most cases, the bowel is moved back to its natural outlet at the anus as soon as the healing process allows.
There are also newer treatment approaches for anal fistulas, such as laser therapy, certain tissue adhesives (fibrin glue) or the use of stem cells. However, little is known about the success of these procedures, so they are not among the established standard procedures.
Follow-up treatment
After surgical treatment of the anal fistula, careful wound care is very important for follow-up treatment. This includes, for example, sitz baths with skin-soothing additives (such as camomile) and rinsing with disinfectant solutions (such as H2O2 or ethacridine).
To prevent pain during bowel movements and to protect the wound area, it is also important that the stool remains as soft as possible. This can be achieved by using agents that loosen the stool (e.g. lactulose). Also make sure you eat a diet rich in fiber and drink plenty of fluids – preferably mineral water or unsweetened herbal teas.
An anal fistula does not heal on its own and always requires medical treatment. If left untreated, an anal fistula can be dangerous, especially if a bacterial infection is present. If the organism is unable to fight the pathogens itself, there is a risk of blood poisoning (sepsis) in the worst case.
In addition, an untreated fistula in the anus will continue to grow and make subsequent treatment more difficult. Under certain circumstances, the sphincter muscle at the anus may be affected to such an extent that control over the stool is lost. This leads to fecal incontinence.
Symptoms
An anal fistula causes various symptoms. Pain often occurs during bowel movements and when sitting. If the fistula tract is open, those affected usually also notice secretions in the anal region. These are watery, bloody or purulent and may also contain stool.
If an anal fistula is caused by an anal abscess, those affected sometimes feel a painful swelling in the anal region. The infection also causes general symptoms such as fever, malaise and fatigue.
Diagnosis
During the examination, the doctor examines the affected region and palpates it carefully. In some cases, he will feel the fistula tract as a hard cord.
If a fistula opening is visible on the outer skin of the anal region, the fistula tract is usually probed. This allows the doctor to determine how the fistula tract runs and whether it is passable. In some cases – for example, if the fistula tract cannot be completely probed – the doctor will use a dye solution to check its patency.
Using an ultrasound probe inserted into the rectum (transrectal sonography), the course of the fistula and any anal abscess can be detected.
If there is a suspicion of certain concomitant diseases (such as tumors) or if the previous examinations do not provide clear findings, magnetic resonance imaging (MRI) is performed in rare cases.
Prognosis
The course of an anal fistula also depends on its anatomical location and whether it is occurring for the first time or has already been treated several times. Frequent operations in the anal area carry the risk of damaging the sphincter muscle and causing fecal incontinence. The risk of faecal incontinence is higher in older women who have had children than in other groups of people.
Prevention
There are no specific measures that can be taken to prevent anal fistulas. However, the risk of certain diseases and factors that promote anal fistulas can be reduced to a certain extent.
The following measures are useful to counteract favorable factors:
- Avoid being overweight. Obesity is a risk factor for diabetes mellitus, among other things.
- To ensure proper digestion, eat a healthy, balanced diet with plenty of fiber, fresh fruit and vegetables every day and drink plenty of fluids (mineral water, herbal teas).
- Make sure you get enough daily exercise. Predominantly sedentary activities increase the risk of anal fistula. Standing desks and height-adjustable desks offer the opportunity to change position while working.
