Anal fistula does not appear suddenly — it is the end result of a step-by-step disease process that usually begins with a simple gland infection. Understanding this progression explains why the condition becomes chronic and why it tends to flare up and settle down in repeated cycles.

Step 1: Infection of the Anal Glands

Deep within the anal canal lie small glands called anal crypt glands, which normally secrete mucus to ease bowel movements. When these glands get blocked — often due to trapped stool debris, chronic constipation, or minor trauma — bacteria multiply inside them, leading to a localized infection.

Step 2: Formation of an Abscess

Once infection sets in, the body’s inflammatory response causes pus to accumulate at the site, forming an anorectal abscess. This is typically the acute, painful stage of the disease, and often the first sign a patient notices, with symptoms such as:

• Throbbing pain near the anus
• Swelling and redness
• Fever and general discomfort
• A tender lump that may feel warm to touch

Step 3: Rupture or Drainage of the Abscess

An abscess under pressure eventually needs an outlet. This happens in one of two ways:

• Spontaneous rupture – the abscess bursts on its own through the skin, releasing pus and providing temporary relief from pain
• Surgical drainage – a doctor incises and drains the abscess to relieve pressure and infection

While this brings quick relief from acute pain, it does not address the deeper problem — the infected gland at the source often remains connected to the drained opening.

Step 4: Formation of the Fistula Tract

Once the abscess drains, the pathway it created between the infected internal gland and the external skin opening can persist as a permanent tunnel, known as the fistula tract. Instead of healing shut, this tract becomes lined with unhealthy tissue that keeps the connection open, allowing the two ends to communicate indefinitely.

Step 5: The Active–Inactive Cycle

This is what makes anal fistula particularly frustrating for patients — it rarely stays in one state. It typically cycles between two phases:

• Active phase: The tract becomes infected again, causing pain, swelling, and pus or blood-stained discharge, sometimes with an associated abscess flare-up
• Inactive (quiescent) phase: The discharge reduces or stops, pain settles, and the external opening may even close temporarily, giving a false impression of healing

However, because the internal opening and diseased tract remain intact beneath the surface, the cycle repeats — often triggered by minor blockage of the tract, lowered immunity, or simply the passage of time. Each cycle can worsen the tract’s complexity, sometimes causing new branches or additional openings to form.

Why This Cycle Matters for Treatment

This on-and-off pattern often misleads patients into thinking the problem has resolved during a quiet phase, delaying proper treatment. Since the underlying tract does not heal on its own, medicines can only calm an active flare-up temporarily — the fistula tract itself needs to be surgically or para-surgically addressed to break this cycle permanently.

This article is for informational purposes only. Anyone experiencing symptoms of anal fistula should consult a qualified physician for proper diagnosis and treatment.