What Is an Anal Fistula?


Anal Fistula, What Is an Anal Fistula, Anal Canal


An anal fistula is a small channel that makes an abnormal connection between the end of the bowel and the skin near the anus. More often than not, anal fistulas start from an infection near the anus that causes a collection of pus (abscess) in the nearby tissue. 


“The collection of pus grows and stretches the skin through the lining of the anus. Thus a connection is formed between the skin and anus. Surgery to drain away the pus may also leave a small channel behind. This is known as an anal fistula, and it may cause bleeding and discharge when passing motion, and can be painful.”

Dr Ganesh Ramalingam


What Causes Anal Fistulas?


When 30-year-old Gillian Kane developed an abscess and underwent emergency surgery, she thought her worries were over until she discovered that she had an anal fistula.


Most anal fistulas develop as a result of anal abscesses. Anal fistulas are formed as a reaction to an anal gland with a pus-filled infection (anal abscesses). They can occur if the abscess does not heal properly after the pus has drained away on its own.


A small number of fistulas may be caused by other conditions such as Crohn’s disease, sexually transmitted diseases, tuberculosis, diverticulitis, cancer, or surgery near the anus. These affect your lower digestive tract or anal area and increases your risk of anal fistula.


What Are the Risk Factors That Cause Anal Fistulas?


Anal Fistulas have an increased risk of development under certain conditions. They are:


  • A medical history of anal abscesses or fistulas
  • Crohn’s disease (a condition causing inflammation of the digestive tract)
  • Ulcerative colitis (a condition that causes irritation, inflammation, and ulcers in the lining of your large intestine)
  • Diverticulitis (a condition that causes inflamed pouches in the lining of the intestine)
  • HIV
  • Cancer
  • Tuberculosis
  • Trauma
  • Radiation therapy


What Are the Symptoms or Warning Signs if I Have Anal Fistulas?


The end of the fistula may be visible as a hole in the skin around the anus, though it may be difficult for you to see it yourself.


Common symptoms of anal fistula include:


  • A constant and throbbing pain that may worsen when you move about, sit down, cough, or have a bowel movement
  • Skin irritation around your anus
  • Swelling or redness around your anus
  • Discharge of blood or pus when you go to the toilet
  • Fever


How Can Anal Fistulas Be Prevented?


Anal fistulas can be prevented by practising good dietary, lifestyle and bowel habits. These habits include:


  • Getting sufficient dietary fibre
  • Drinking an adequate amount of water
  • Keeping active and exercising regularly
  • Not delaying your bowel movement 


Eating fibre-rich foods may help prevent constipation. This helps to prevent the formation of large, hard, or dry stools, which may lead to an anal fissure. Simultaneously, consuming sufficient fibre will help your stools soften while promoting more frequent bowel movements.


Staying hydrated and drinking sufficient water is another key that may help prevent constipation. By adding enough fluid to your system, it makes stools softer and easier to pass. 


A lack of physical activity is one of the most common causes of constipation. Keeping active may help ensure that your digestive system is kept in reasonable condition while promoting bowel movement. 


Holding your bowels in when it is time to pass may lead to harder stools. As stools get dryer and harder with time, they get tougher to pass if held in the body for too long.


How Are Anal Fistulas Diagnosed?


Our doctor will perform a physical and rectal examination for you to check for signs of an anal fistula. This is done by examining the skin around your anus and looking for an external opening in your skin. If it is possible, the depth and direction of your fistula tract will be determined.


Anoscope, Anal Fistula, Anal Disease


Otherwise, our doctor may use an anoscope, a special instrument that helps him see inside your anal canal. Further imaging tests such as an ultrasound, CT scan, or MRI scan may be used to provide images of the affected area for diagnosis.


What Are the Potential Complications of Anal Fistulas?


Complications of an anal fistula may result in a recurring fistula after treatment. Anal fistulas, when untreated, may also lead to faecal incontinence (an inability to control bowel movements). This condition occurs when some of the muscles around the anal sphincter are removed.


How Are Anal Fistulas Treated?


A physical examination of the affected area is typically used to diagnose an anal fistula. Your doctor may check for pain, redness and swelling in the anal region while observing if further investigations are required. If a patient is experiencing severe pain and drainage near the area of the fistula, it could be a sign of infection.


For anal-rectal fistulas, your doctor may deploy a sigmoidoscope to conduct an internal examination of the fistula. This investigation not only helps our doctor determine the location and cause of the fistula. It also helps identify signs caused by Crohn’s disease. Depending on the situation, surgery may be recommended. This procedure is known as fistulectomy.


In some instances of deeper perianal abscesses, where the signs are not immediately visible, an endoscope may be used to look inside the anal canal and lower rectum. 


Our doctor may also arrange for an imaging test such as a CT scan, ultrasound, or MRI for a more accurate diagnosis.


Treating anal fistulas can be challenging if they get too large. Such was the case of a 36-year-old patient suffering from a 25-cm fistula. While the average size of an anal fistula is about 3 to 5cm, the patient, Siraj Ahmed, was suffering from a rare kind of fistula, which had reached into his scrotum, up to the root of his penis. 


Thankfully, despite his procedure’s complexity, doctors were able to deploy a technique called Video Assisted Anal Fistula Treatment (VAAFT) to treat his condition. 


What Happens During a Fistulectomy?


A fistulectomy is performed to completely remove an anal fistula. This procedure removes the entire fistulous tract but may pose a risk of damage to the anal sphincter. 


This procedure may be recommended for patients experiencing a high likelihood of recurrence or who have large amounts of tissue that is blocking the sphincter’s normal function.  


The procedure does not require an inpatient stay, so patients are usually discharged within the day.


For conditions where the fistula is assessed to be small or shallow, the procedure may be done at the doctor’s clinic with the administration of local anaesthesia.


Recounting his experience with what he calls an enormously painful perianal abscess, Brandon shares his story with Crohn’s & Colitis Foundation.


He was directed to a colorectal surgeon who attempted to cut and drain the abscess.


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