Anal fistula

What is an anal fistula?

An anal fistula is an anomalous, inflammatory connection that forms between the anal canal and the skin. In most cases, this develops as a result of an untreated anal abscess. The abscess is caused by an infection, often resulting from a blockage of the anal canal glands. The formation of a fistula allows secretions such as pus, blood, and inflammatory tissue to escape from the internal fistula tract to the outside. This can lead to persistent inflammation and pain.

There are various types of anal fistulas, which differ in their location and course:

• Inter-sphincteric fistulaThis fistula runs between the internal and external sphincter muscle and is the most common form.
• Trans-sphincteric fistulaThis fistula crosses both the internal and external sphincter and usually requires more complex treatment.
• Extra-sphincteric fistula: This runs above the sphincter muscles and often has a prolonged and complex course. It can arise from a more severe infection, such as in patients with Crohn’s disease.

The development of an anal fistula can extend over months or even years. It often remains unnoticed for a long time, especially if it begins with a small, superficial abscess. Without adequate treatment, however, a complex system of fistula tracts can develop, complicating treatment.

Anatomical basics

Understanding the anatomical structures around the anal canal is crucial for comprehending anal fistulas. The anal canal is permeated by glands responsible for regulating moisture and protecting the anal canal. If one of these glands becomes infected or blocked, an abscess can develop, which in the

worst case leads to a fistula. Since the anal canal is surrounded by several layers of muscles, particularly the internal and external sphincter muscles, the fistula’s course can run through or around these muscles.

Causes and risk factors

The development of anal fistulas can be promoted by various factors and pre-existing conditions. In most cases, the cause is a bacterial infection leading to an anal abscess. If such an abscess is not treated promptly, a fistula develops from the accumulation of pus and inflamed tissue. However, there are also a variety of other causes and risk factors:

Primary causes

1. Anal abscesses: The most common cause of anal fistula formation. These occur when the anal glands become infected by bacteria. If the abscess spreads into the deeper tissue layers of the anal canal, fistula formation can occur.
2. Chronic inflammatory bowel disease (IBD): Conditions such as Crohn’s disease and ulcerative colitis are often associated with the formation of anal fistulas. In patients with Crohn’s disease, up to 30% develop perianal fistulas, as deep tissue inflammation damages the mucous membrane of the intestine and anal canal.
3. Anal infectionsInfections caused by sexually transmitted diseases, such as chlamydia or syphilis, can also lead to damage to the anal canal and promote the development of a fistula.

Secondary causes and risk factors

• Traumatic injuries: Surgical procedures or injuries to the anal area can lead to the formation of fistulas. For example, a postoperative abscess can transform into an anal fistula.
• Immunosuppressive conditionsPatients with a weakened immune system, such as those with HIV or after an organ transplant, have an increased risk of developing an infection that can lead to fistula formation.
• Genetic predispositionThere is evidence that genetic factors may play a role in the development of anal fistulas, particularly in patients with chronic inflammatory bowel disease.

Symptoms and complaints

The symptoms of an anal fistula vary depending on the severity and course of the condition. While some patients experience only mild discomfort, others suffer from chronic pain and recurrent infections. Common symptoms include:

1. Pain in the anal area: These typically occur when sitting, walking, or during bowel movements. The pain can be acute or dull and often intensifies during bowel movements.
2. Secretion of pus or blood: A characteristic sign of an anal fistula is the discharge of pus or blood from an opening in the skin near the anus. This discharge can be intermittent and lead to unpleasant odors.
3. Swelling and rednessInflammatory swelling or redness in the anal area indicates an active infection or abscess.
4. Itching and irritationThe constant secretion of pus and fluid can cause skin irritation and severe itching.
5. Occasional fever and general feeling of illnessIn the case of severe or chronic inflammation, fever, chills and a general feeling of illness may occur.

Many patients report a constant, uncomfortable pressure sensation in the anal area, caused by inflammation and swelling. These symptoms can become chronic if the fistula is not treated.

Diagnosis of an anal fistula

The diagnosis of an anal fistula begins with a thorough medical history and physical examination by a specialist in proctology. The doctor will examine the anal area and look for signs of an external opening of the fistula or inflammatory processes. As anal fistulas often run deep in the tissue, additional diagnostic measures are required to determine the exact course of the fistula.

1. clinical examination

During the physical examination, the doctor will look for visible signs of a fistula. This may be a small opening near the anus from which pus or fluid is draining. Often, the doctor will palpate the fistula tract to determine if there is a connection to the anal canal.

2. imaging procedures

As many fistulas have complex courses, imaging procedures are essential to determine the exact location and course of the fistula.

• Endoanal ultrasound: Ultrasound provides detailed information about the course of the fistula in relation to the sphincter muscles. This method is particularly useful for determining whether the fistula traverses the sphincter muscle and which surgical method should be considered.
• Magnetic resonance imaging (MRI): MRI is the most precise imaging method for mapping the course of the fistula, especially in complex or extra-sphincteric fistulas. It allows the doctor to visualize the entire fistula tract and any secondary fistulas.
• Contrast fistulography: In rare cases, a contrast agent is injected into the fistula to make its course visible on an X-ray. This is primarily used for very deep fistulas.

3. fistula probing

In some cases, during a short operation, the doctor may insert a probe into the fistula tract to check its course. This method is mostly used in conjunction with surgical treatment to fully open and treat the fistula.

Treatment options

The treatment of anal fistulas depends on the type and severity of the fistula. While smaller and simple fistulas can often be treated conservatively, more complicated or deeper fistulas require surgical intervention. There are various approaches that can be applied, both conservative and surgical.

1. conservative therapy approaches

In some cases, anal fistulas can be treated conservatively, especially if the fistula is small and does not cause severe discomfort:

• Change of dietA high-fiber diet can soften the stool and reduce the strain on the anal canal, leading to symptom relief.
• Topical applications and sitz bathsSitz baths with antiseptic or anti-inflammatory additives can help to relieve symptoms and reduce inflammation.
• Antibiotics and painkillersIn the case of acute inflammation or infection, antibiotics can be administered to bring the infection under control.

2. surgical procedures

However, most anal fistulas require surgical treatment to completely remove the fistula and promote the healing process. The most common procedures include:

• Fistulotomy: This is the most commonly performed operation for simple fistulas. The fistula tract is incised and left open to heal from the inside out. This method is particularly effective for simple, intersphincteric fistulas.
• Seton method: For complex or transsphincteric fistulas, a seton (an elastic thread) is passed through the fistula tract to allow continuous drainage and promote healing. The seton can either remain loose or be slowly tightened to gradually close the fistula tract.
• Advancement flap process: In this technique, the fistula is removed, and the opening is closed with a healthy tissue flap. This method is particularly suitable for complex fistulas or those that traverse the sphincter muscle, as it protects the integrity of the sphincter muscles.
• VAAFT (Video-Assisted Anal Fistula Treatment)This is a minimally invasive method in which a camera is inserted into the fistula tract to visualize the fistula tract.

to view from the inside and treat with a special instrument. This method has the advantage of being very precise and tissue-sparing.

3. modern technologies

In addition to the classic surgical procedures, there are also innovative, minimally invasive techniques that are used in the treatment of anal fistulas:

• Laser therapy: In this method, a laser is used to close the fistula tract from the inside. The advantage of this method lies in its minimal invasiveness and faster healing.
• Stem cell therapy: In modern fistula treatment, stem cells are increasingly used to promote tissue healing and reduce the risk of recurrence. This method is mainly used in patients with chronic inflammatory bowel diseases.

Risks and complications

Although surgical treatment of anal fistulas is successful in most cases, some risks and complications can occur. The most common include:

• Postoperative incontinenceIn some patients, especially if the fistula traverses the external sphincter, damage to the sphincter may occur, which in rare cases can lead to fecal incontinence.
• Recurrences: One of the biggest challenges in treating anal fistulas is the risk of recurrence. Even after successful surgery, a new fistula can form in some cases, especially if the fistula is complex or was not completely removed.
• Wound healing disordersIn rare cases, delayed or impaired wound healing may occur, especially in patients with a weakened immune system or chronic inflammatory diseases.

Prognosis and prospects of recovery

The prognosis after anal fistula treatment is generally good, especially if the fistula is diagnosed and treated early. For simple fistulas treated surgically, the cure rate is over 90%. Most patients can resume their normal activities within a few weeks. However, the chances of healing depend heavily on the chosen treatment method and the complexity of the fistula.

In patients with chronic inflammatory bowel diseases or complex fistulas, the prognosis may be less favorable, and there is a higher risk of recurrence. Regular follow-up and monitoring by the treating physician are essential in these cases to prevent recurrence.

 

Prevention of anal fistulas

The prevention of anal fistulas begins with avoiding anal abscesses and other inflammatory processes in the anal area. Here are some measures that can reduce the risk of fistula formation:

1. High fiber dietA diet rich in fiber promotes healthy digestion and reduces the risk of constipation, which can lead to increased pressure in the anal canal.
2. Adequate fluid intakeAdequate fluid intake keeps the stool soft and facilitates bowel movements, which reduces pressure on the anal canal.
3. Regular exercisePhysical activity promotes blood circulation throughout the body, including the anal area, and can therefore support the health of the anal glands.
4. Good hygieneRegular and gentle cleaning of the anal area can reduce the risk of infection and resulting fistula formation.

Patients with chronic inflammatory bowel disease should pay particular attention to the care of their anal area and visit their doctor regularly in order to recognize and treat inflammation at an early stage.

Anal fistula and related diseases

Anal fistulas often occur in conjunction with other proctological conditions. It is important to know the differences between these conditions to ensure correct diagnosis and treatment:

• Hemorrhoids: Although hemorrhoids and anal fistulas can cause similar symptoms such as pain and bleeding, they are two different conditions. Hemorrhoids are swollen blood vessels in the anal area, while anal fistulas are inflammatory connections. However, both conditions can occur simultaneously and require targeted treatment.
• Anal abscesses: An anal abscess is the most common cause of an anal fistula. While an abscess represents an accumulation of pus in the tissue, the fistula is the permanent channel that forms as a result of the abscess. It is important to treat an abscess promptly to prevent the formation of a fistula.
• Crohn’s disease: Patients with Crohn’s disease have an increased risk of developing anal fistulas due to the deep tissue inflammation associated with this chronic bowel disease. Treatment of fistulas in Crohn’s disease often requires special anti-inflammatory therapies to control the underlying condition.

Conclusion

Anal fistulas are a painful and distressing condition that requires careful diagnosis and targeted treatment. Thanks to modern medical

technologies and surgical procedures, however, the healing prospects for most patients are good. Early diagnosis and treatment are key to successful healing and preventing complications. Patients should consult a proctology specialist at the first signs of an anal fistula to ensure timely therapy. With a healthy lifestyle and regular medical check-ups, most patients can minimize the risk of developing an anal fistula.