Fistula: What It Is and Where It Can Occur on the Body

A fistula is a narrow channel that connects body cavities or hollow organs to each other or to the external environment. It may open onto the skin or onto a mucous membrane. Below are the definition, the mechanism of formation, typical locations on the body, and how doctors recognize a fistula.

What a fistula is

A fistula (from the Latin fistula — "tube") is a channel connecting body cavities, including pathological ones, or hollow organs to the external environment or to each other. It usually appears as a narrow channel lined with epithelium or granulation tissue. A distinction is made between fistulas that arise as a result of a pathological process and fistulas created surgically to drain the contents of a hollow organ. Fistulas can be congenital or acquired, external (opening onto the skin) or internal (opening onto the mucous membrane of hollow organs).

How a fistula forms

Pus formed during the breakdown of an inflammatory focus makes its way outward. The channel through which the pus drains usually heals after the inflammation is eliminated. If the inflammatory process is not resolved and an infected cavity remains deep in the tissues, sometimes with a sequestrum, the channel does not close and a purulent fistula forms. Such fistulas occur with suppuration of sutures around ligatures, around foreign bodies and bone sequestra left deep in the tissues. Other causes include postoperative complications, trauma, infection, and diseases such as Crohn's disease or ulcerative colitis.

Fistula on the skin and body

An external fistula opens onto the skin, and its opening is visible as a hole with discharge. A purulent fistula forms if an infected cavity remains deep in the tissues: as long as it persists, the channel does not close and discharge continues.

Fistula near the anus

An anorectal fistula is a pathological channel running from the anus or rectum to the skin; a pararectal fistula runs from the anal crypt outward to the skin. Most often an anal fistula develops after an anal abscess if it has not healed properly after the pus drains. Less common causes include Crohn's disease, diverticulitis, hidradenitis suppurativa (a long-term skin disease with abscesses and scars), tuberculosis or HIV, and complications of surgery near the anus. Symptoms: irritation of the skin around the anus, constant throbbing pain that worsens when sitting, moving, defecating or coughing, foul-smelling discharge, pus or blood during defecation, swelling and redness, and, with an abscess, high fever. Sometimes the end of the fistula is visible as a hole in the skin near the anus.

How a fistula is diagnosed

The doctor asks about symptoms and bowel diseases, examines the skin around the anus, and may offer a digital rectal examination. If a fistula is suspected, the patient is referred to a colorectal surgeon. Possible examinations:

• repeat physical and rectal examination;
• proctoscopy — examination inside the anus with an instrument with a light at the end;
• ultrasound examination;
• MRI or CT.

When to see a doctor

You should see a doctor for persistent symptoms of an anal fistula: constant pain, discharge, skin irritation. Anal fistulas usually do not heal on their own, and surgery is recommended in most cases; the options for intervention and their risks are discussed with the surgeon. Signs that require an immediate call for emergency services:

The presence of a fistula by itself is not a reason to call emergency services; 103 or 112 — for a sharp deterioration in condition that threatens life.

This material is for reference: it describes the phenomenon and does not replace consultation with a doctor, who will assess your specific situation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer