Anal Fistula - Symptoms, Diagnosis and Treatment

Anal Fistula - Symptoms, Diagnosis and Treatment


  • Symptoms of anal fistula are discharge and pain in the anal area and sometimes bleeding. These are similar to symptoms experienced with hemorrhoids so an examination should be carried out by a doctor to ensure proper diagnosis and treatment.
  • Anal fistulas do not heal on their own and are often chronic issues. In order to cure an anal fistula, minimize the chance of recurrence, and avoid fecal incontinence, surgery performed by a specialist is necessary.  
  • Surgical treatment of anal fistulas can be performed in a number of different ways, depending on the type of fistula and the symptoms experienced. The success rate, chance of recurrence, and advantages and disadvantages of each method differ accordingly; the doctor will consider all factors and select the surgical treatment most suitable for the patient.

Anal fistula is a name not very familiar to most people. In fact, it’s a disease that can occur in patients of all ages and genders and is found fairly frequently, no less so than other intestinal and rectal disorders. Because anal fistula occur on the buttocks and near to the anus, patients often feel embarrassed or put off seeing a doctor, even when they experience symptoms or are suffering as a result. However, failing to treat the problem simply causes even more chronic or serious symptoms, making it more difficult for doctors to treat and often causing further complications as well.

What is an Anal Fistula?

An anal fistula is caused by a chronic infection in the anal area. It can be described as a narrow tunnel that connects an external opening in the skin near the anus with an internal opening in the anal canal. It can occur around the anus and the buttocks and generally looks like a red, swollen bump, often filled with pus. Anal fistula can be divided into 2 main types:

  • A simple anal fistula is one that is relatively shallow and barely passes through the anal sphincter, making treatment fairly simple and uncomplicated.
  • Complex anal fistulas can take a variety of forms. For example, they may be quite deep, or they may follow a curved course from the inner opening to the outer one, or they may have one internal opening but branch into multiple tracks and external openings, etc. All of these factors make complex anal fistulas more difficult and complicated to treat.

Causes of an Anal Fistula

An anal fistula is caused by inflammation, blockage, and bacterial infection of the anal glands, sometimes originating in the intestines and entering through the internal opening in the anal canal. As the infection and blockage grows, the bacteria buildup causes the nearby formation of infected tissue and pus. As the pus accumulates, it gradually makes its way through layers of muscle until it forms a connecting cavity between the anal canal and the surface skin near the anus so that it can drain, resulting in an anal fistula. Sometimes a fistula is a result of a perianal abscess that was drained surgically.

Symptoms of an Anal Fistula

  • Swelling, redness, and itching around the anal area
  • Yellow discharge/pus or bleeding near the anal opening
  • Pain in the anal area
  • Holes or hardened tissue around the anus

How are Anal Fistulas Different from Hemorrhoids?

Both diseases have similar symptoms: blood mixed with stools and pain in the anal area. Hemorrhoids, however, involve swollen veins in the anus and rectal area, causing a soft lump to protrude from the anus. There may be some pain from time to time but there is usually no pus discharge. In the case of anal fistulas, on the other hand, they usually look like a hard lump and generally cause a lot of pain, along with discharge or pus, and sometimes bleeding from the anal area as well. Additionally, hemorrhoids can be cured with behavior adjustment, rubber band ligation and injection treatment, while anal fistulas require surgery performed by specialized doctors.

Can Anal Fistula Heal on Its Own? When Should I See a Doctor for Treatment?

Anal fistulas do not heal on their own and are often chronic. In order to be effectively treated and cured with a low chance of recurrence and without the possibility of incontinence, it is necessary to undergo surgery. If you experience pain or pus discharge in the anal area, you should seek medical attention as quickly as possible for the most appropriate diagnosis and treatment.

Diagnosis of Anal Fistula

  • Review of the patient’s medical history: The specialist will begin the diagnosis by asking about your symptoms and your medical history.
  • Physical examination: The doctor will examine the skin around the anal area to look for redness, pus, bleeding, etc.
  • MRI: If a complex fistula is suspected or the fistula is more difficult to find, your doctor may consider an MRI scan to get a better, clearer view of the fistula tract between the inner and outer openings. This allows the doctor to provide the most accurate and effective treatment.

Is There Any Non-surgical Treatment for Anal Fistula?

At present there is not. Anal fistula can only be treated surgically.

Treatment Methods for Anal Fistula Surgery

There are several surgical methods which can be used, depending on the fistula's location and complexity. In principle, however, the goals of the surgery are to remove the anal fistula completely, to prevent recurrence and to protect the sphincter muscles, as damage to these muscles can lead to fecal incontinence.

Simple Anal Fistula

Simple anal fistulas can be treated with open surgery (Fistulotomy or Fistulectomy). In a fistulotomy, the surgeon makes a small cut in the fistula's internal opening to scrape and drain out all the pus and infected tissue. A fistulectomy involves the removal of the whole fistula tract. The wound will be left to heal naturally, with new tissue growing and filling the gap. It takes about one month for this tissue to heal. Fistulectomy provides about a 90% cure rate with only about a 10% chance of recurrence. However, this method can result in side effects—patients may experience fecal incontinence if the doctor is not skilled enough and the sphincter muscles are excessively cut. For this reason, it is vital that the surgery be performed by a highly skilled and experienced doctor.

Complex Anal Fistula

In the case of deep or multi-tract fistulas, the fistula tract cannot be removed entirely, as this would require too much of the sphincter muscle to be excised resulting in fecal incontinence. For this reason, other surgical methods are necessary:

  • LIFT (Ligation of Intersphincteric Fistula Tract) is an operation to close off the internal opening of the fistula in order to prevent bacteria inside the anus from entering the cavity. This type of surgery does not damage the anal sphincter and patients can rest assured they will not experience problems with incontinence post-surgery.
  • Seton Placement involves the placement of a silk or latex string (seton) into the fistula to help drain the infection. The seton is progressively tightened, making the fistula smaller and smaller behind it and allowing the body to gradually heal the wound and repair itself.  With this method, although setons do slowly cut through the anal sphincter, it is done in such a way that the body has the time to repair the tissue gradually and continually throughout the procedure, thereby avoiding fecal incontinence.
  • Advancement Rectal Flap involves taking mucosal tissue from the lining of the rectal wall before removing the fistula's internal opening. The flap is then used to cover the repair. The principle of this treatment is to close up the internal opening and thus prevent the entry of bacteria from the inside, allowing the external portion to heal gradually. 
  • Laser treatment involves the insertion of a laser probe into the external opening of the fistula in order to close up the entire tract(s). Energy from the laser gradually destroys the abscessed tissue, shrinking it into scar tissue. As the laser is slowly drawn back through the fistula from the inner opening to the outer opening, it seals and closes up the channel behind it.

Of the 4 surgical methods outlined above, there is no method considered to be 100% effective. Rather, each of these has about 60-70% effectiveness; that is, there is still some chance of recurrence. That said, in all of these cases, a great advantage is that these treatment methods can all be repeated if they are not successful on the first try, as the anal sphincter will not have been removed or excessively cut during the procedure. 

Preparation Before Surgery

  • Laboratory examinations, such as a blood test, urinalysis, EKG, X-rays, and other tests are carried out at the discretion of the doctor. In the case of any abnormal results from the physical examination, doctors specializing in other medical fields may be consulted.
  • If the patient has an underlying or chronic disease and takes certain medications regularly, particularly any medications that affect blood clotting such as aspirin, warfarin, etc., such drugs should be discontinued for 5-7 days prior to surgery.
  • If there is a large amount of blood or pus discharge from the fistula, a gauze pad or sanitary pad can be placed over the abscess for protection.
  • If the patient is experiencing a lot of pain, pain medications can be helpful, as can drinking large amounts of water.
  • The patient should refrain from activities that could cause impact or force to the buttocks or anal area to avoid unnecessary pain.

Recovery Period and Post-Surgical Self-Care

For simple fistula surgery, just a one-day hospital stay is necessary. For complex fistula surgery, patients should expect to stay in the hospital for 1-2 days. Patients can then adhere to the following post-surgical self-care methods:

  • Clean the wound carefully at home with mild soapy water, and then rinse it with clean tap water regularly—in the morning, in the evening, and after bowel movements—and then gently pat the area dry with a clean cloth. This should be done until the wound heals, which generally takes about 4-6 weeks.
  • Put a gauze pad or a sanitary pad or napkin over the wound to absorb any bleeding or discharge and prevent it from getting on clothing.
  • Eat normally. For example, there is no need to limit the diet to soft foods.
  • After surgery, the doctor may prescribe laxatives or stool softener medications to help with bowel movements.
  • The doctor may also prescribe other medications based on the patient’s condition, such as painkillers or antibiotics.
  • Recuperate an additional 2-3 days at home before driving again.
  • Avoid exercising or other physical activities at the discretion of the physician.

Risks, Side Effects, and Chance of Recurrence

A key priority for doctors will be to avoid fecal incontinence caused by the removal of too much of the sphincter muscles or cutting into them. As such, the doctor will select a surgery method that is most suitable for the patient after assessing the type of anal fistula—simple or complex, deep or shallow, etc. In addition, the expertise of the surgeon is an important consideration for this type of procedure. After the surgery is carried out, the chance of recurrence differs greatly depending on the fistula type.

How to Prevent Recurrence

Patient practices and self-care of postoperative wounds are important aspects in minimizing the chance of recurrence. Methods used for the prevention of recurrence are:

  • In the case of simple fistula surgery, doctors recommend postoperative care of the wound in order to prevent recurrence. The patient can do this by gently patting the scar area with their fingers each day to prevent the skin from joining together incorrectly and possibly creating a new cavity. This advice is important as, if followed correctly, the chance of recurrence is less than 10%.
  • In the case of complex fistula surgery, regardless of the surgical method employed, patients will have a 20-30 percent chance of recurrence. The advantage, however, is that even if the patient does experience recurrence, the original treatment method can be repeated as many as 2-3 times, as there will not have been too much cutting into, or loss of, the sphincter muscles and thus the patient does not have to worry about fecal incontinence issues.

In the past, when an abscess occurred on the buttocks, it would likely be treated using perforation to drain the pus from the abscess. However, there was no additional physical examination involved, which meant that if it was punctured, the inner and outer openings still remained and could turn into a fistula. Nowadays, however, a skilled doctor will perform a physical examination beforehand and, if an abscess is found that has no external opening, the surgeon will examine it once again during surgery to see if there is any internal opening. If any such opening is found, it can be cut off immediately to prevent any cavity being left that could develop into a more chronic condition and, eventually, an anal fistula.

Bangkok’s Most Trusted Surgical Team

Catering to the international and local Thai communities, the Surgery Clinic at Samitivej, Bangkok adheres to the highest standards of quality. Led by a team of certified surgeons with years of combined experience, our clinic is proud to perform safe, effective operations for all who require them. We understand that finding the right surgeon is critical and ensure that we choose only the very best to work on our team. It is in acknowledgement of this commitment to excellence that our hospital has received the prestigious JCI accreditation, the highest recognition that an international hospital can obtain.

Samitivej has a team ready to help and provide services for: 

  • Treatment Plan Consultation with a doctor via online video-call (second opinion)
  • Treatment Planning if you have medical records or a price estimate from another hospital 
  • Cost Planning by our Appraisals Team with price guarantee (only for procedure packages without complications)
  • Check Initial Coverage Eligibility with Thai and international insurance companies (only for insurance companies in contract with the Hospital)

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