Anal fistula(s) develop as a result of infected anal glands that can lead to the formation of abscesses. Less common causes of anal fistulas include:

• Crohn’s disease (a condition where the digestive tract becomes inflamed leading to severe pain and diarrhea).
• Hidradenitis suppurativa (a skin condition that results in the formation of small painful lumps under the skin that can break open or form tunnels under the skin. It is believed to be an inherited condition).
• Diverticulitis (a condition where small bulging pouches or diverticula develop in the digestive tract. When these pouches become infected, it's called diverticulitis).
• Tuberculosis (bacterial infection of the lung).
• Sexually transmitted diseases (infections that can be transmitted through sexual intercourse) such as HIV (human immunodeficiency virus).
• Trauma and in some cases, even cancer.

An anal fistula can appear as a boil-like opening near your anus and it may discharge pus or blood which will be visible while passing stools. In some cases, there will be an opening in the skin around the anus, whereas in other cases, it can be a blind-ending tunnel that ends below the skin. Often the skin around the anus is red and inflamed. 

Other symptoms of anal fistulas include:

• Painful bowel movements (the process of passing stools)
• Irritation of the skin around the anus
• Foul-smelling drainage from the opening around the anus
• Fever with/without chills
• Malaise [general feeling of fatigue (tiredness)]

Top diagnose an Anal Fistula, the doctor will go over the patient’s medical history and perform a physical exam. The doctor will examine the area around the anus to see if there is any opening (a fistula tract) on the skin.

The doctor may recommend additional tests such as:

• Anoscopy: This method uses a thin flexible tube that is inserted into the anus to visualize the anal canal and rectum. 
• MRI (magnetic resonance imaging) is done to identiy the fistula tract, sphincter muscles and other structures.
• Endoscopic ultrasound: This uses high frequency sound waves to identify the fistula tract, sphincter muscles and other structures. 
• Fistulography: In this test a contrast dye is injected and the x-ray is done to identify the fistula tract.
• Fistula probe: The doctor will insert an instrument (fistula probe) to check the length of the fistula.
• Flexible sigmoidoscopy: This is a procedure in which the doctor uses a long, flexible tube called a sigmoidoscope that has an attached light and camera at the end to look inside the sigmoid colon and rectum. If there is an underlying condition such as Crohn's disease, blood tests, X-rays, and colonoscopy will be advised.

Once the surgery is completed, the patient will be taken to the recovery room where they will be kept under observation until the anaesthesia wears off. Vitals (heart rate, blood pressure, respiratory rate, pulse rate) will be monitored regularly followed by the need for a catheter (a tube that drains urine from the bladder) at first for passing urine. 

Once the patient feels better, they can get up and walk around as it improves their circulation and helps prevent complications.

The patient may be allowed to go home the same day after your procedure. However, they will be given instructions on how to take care of the wound and other precautions that need to be followed at home. Laxatives recommended by the doctor will help soften the stools and reduce the discomfort. One can aslo use a sitz bath to reduce the irritation and discomfort in the anal region. However, the patient will be advised to sit in a tub of warm shallow water (can be in a bathtub) for 10-20 minutes several times a day. This relaxes the sphincter muscles and promotes healing. One can get back to all the normal activities within 4-5 weeks after the surgery.