Understanding Fistulas: What They Are, Why They Form, and How They're Treated

The word "fistula" might be unfamiliar, but the condition it describes is far more common than most people realize. A fistula is an abnormal passage or tunnel that forms between two organs, cavities, or surfaces that don't normally connect — allowing fluids, waste, or other substances to travel where they shouldn't.

Fistulas can occur almost anywhere in the body. They range from mild and manageable to serious and life-altering, depending on their location and underlying cause. What they share in common is this: they are almost always abnormal, almost always require medical attention, and in the vast majority of cases, they can be treated.

"A fistula is essentially a tunnel the body creates in response to trauma, infection, or disease — and understanding where that tunnel forms tells you a great deal about what caused it." — Cleveland Clinic

WHAT EXACTLY IS A FISTULA?

Under normal circumstances, the organs and cavities in your body are neatly separated. A fistula disrupts that arrangement — forming a channel between two structures that creates an unintended pathway. That pathway may allow stool, urine, pus, blood, or other fluids to travel to places that can cause infection, inflammation, and significant discomfort.

Some fistulas are congenital, meaning they are present at birth due to abnormal fetal development. Others are acquired — developing later in life as a result of injury, infection, surgery, or disease. Notably, not all fistulas are unwanted: physicians deliberately create arteriovenous (AV) fistulas in patients who need dialysis, connecting an artery and vein to produce reliable vascular access for treatment.

Not all fistulas are the same. The term covers a wide range of conditions across the body. An anal fistula, an obstetric fistula, and a dialysis fistula are all very different in cause, location, and management. What they share is the same basic definition: an abnormal connection between two structures.

WHERE FISTULAS OCCUR

• Anal fistula — An infected tunnel between the skin near the anus and the anal canal. Usually develops after an anal abscess. The most common type in developed countries. • Vesicovaginal fistula — An opening between the bladder and vagina, causing urine to leak into the vaginal canal. Often results from pelvic surgery or prolonged obstructed labor. • Obstetric fistula — A devastating childbirth injury caused by prolonged, obstructed labor without access to emergency obstetric care. A major global health concern. • Arteriovenous (AV) fistula — An abnormal or surgically created connection between an artery and a vein. Deliberately created for hemodialysis patients; may also form as a complication of injury or surgery. • Gastrointestinal fistula — A connection involving the GI tract — such as between the intestine and skin, or between loops of bowel. Often linked to Crohn's disease, radiation therapy, or surgical complications. • Tracheoesophageal fistula — A connection between the trachea and esophagus. Most commonly a congenital defect diagnosed in newborns; can also develop in adults as a complication of cancer treatment.

CAUSES OF FISTULAS

The underlying cause of a fistula depends heavily on its location and type. In general, fistulas form when tissue is damaged — by infection, inflammation, injury, or surgery — and the body's healing process creates an unintended channel rather than simply closing the wound. Common causes include:

• Infection or abscess — When an abscess isn't fully treated or drains on its own, it can carve a pathway through surrounding tissue. This is the most common cause of anal fistulas. • Inflammatory bowel disease (IBD) — Crohn's disease in particular is strongly associated with fistula formation due to chronic, deep inflammation of the bowel wall. • Surgical complications — Fistulas can develop when surgical wounds don't heal properly, when tissues are sutured under tension, or when post-operative infection occurs. • Radiation therapy — Radiation to the abdomen or pelvis can damage surrounding tissue and trigger fistula formation, sometimes months or years after treatment. • Obstructed or prolonged labor — Extended pressure from the baby's head against the birth canal can cut off blood flow and cause tissue death, resulting in obstetric fistula. • Congenital defects — Some fistulas are present from birth, resulting from incomplete or abnormal development of organs or tissue structures during fetal growth. • Cancer or tumors — Tumors can erode through tissue and create abnormal connections, and cancer treatment can also be a contributing cause.

COMMON SYMPTOMS

Symptoms vary depending on where the fistula is located, but several warning signs appear across many types: persistent pain or pressure, unusual discharge, leaking urine or stool, recurrent infections, fever or chills, skin irritation or redness, nausea or vomiting, unexplained weight loss, diarrhea or constipation, foul-smelling discharge, pain during intercourse, visible opening near the skin.

Don't dismiss unusual discharge or recurring infections. These are among the most common — and most overlooked — early signs of a fistula. If you're experiencing unexplained, recurrent infections in the same area of your body, speak with your doctor about whether imaging or further testing is warranted.

HOW FISTULAS ARE TREATED

Treatment depends on the type, location, and severity of the fistula, as well as the underlying condition that caused it. Most fistulas do not resolve on their own and require medical or surgical intervention.

1. Medications & antibiotics — For fistulas tied to infection or inflammation (especially Crohn's-related), antibiotics, immunosuppressants, or biologic agents may be used to reduce inflammation and control the underlying condition.

2. Drainage & wound care — When an abscess is contributing to the fistula, draining it is often the first step. Proper wound care after drainage can support healing and prevent recurrence.

3. Endoscopic procedures — Minimally invasive endoscopic techniques can be used to close small fistulas — particularly gastrointestinal ones — without requiring open surgery.

4. Surgery — Surgery is the most common and often most definitive treatment. Procedures vary by location — from fistulotomy (for anal fistulas) to complex reconstructive surgery (for obstetric or pelvic fistulas). Complex fistulas may require more than one operation.

Specialist care matters. Fistulas — especially recurring or complex ones — are best managed by specialists such as colorectal surgeons, urologists, urogynecologists, or gastroenterologists, depending on their location.

WHAT TO KNOW IF YOU OR SOMEONE YOU LOVE IS AFFECTED

Fistulas can be physically painful, emotionally difficult, and — especially when they involve the bowel or bladder — deeply disruptive to daily life and self-confidence. Stigma around the symptoms often delays people from seeking care. But fistulas are medical conditions, not personal failings, and treatment outcomes are generally very good when care is sought early.

If you're experiencing any persistent, unexplained symptoms — especially recurring infections, unusual discharge, or pain in the pelvic or abdominal region — speak with a healthcare provider. Early diagnosis leads to simpler treatment, faster healing, and a significantly better quality of life.

This article is for informational purposes only and does not constitute medical advice. Consult a licensed healthcare provider for diagnosis and treatment recommendations. Sources: Cleveland Clinic, CDC, NIH, 1mg Health, Johns Hopkins Bloomberg School of Public Health, NCBI/PubMed.