Fistulas are more common than most people realize. Anal fistulas alone affect roughly 1 in 10,000 people each year, and other types of fistulas, from obstetric to surgical, add significantly to that number. How common a fistula is depends heavily on which type you’re talking about, where in the world you live, and whether you have certain underlying conditions.
Anal Fistulas: The Most Common Type
Anal fistulas are abnormal tunnels that form between the inside of the anal canal and the skin near the anus. They’re the type most people encounter, and they affect men roughly twice as often as women. The prevalence is about 12.3 per 100,000 in men compared to 5.6 per 100,000 in women. Most develop after an anal abscess drains or fails to heal properly, though they can also form without an obvious trigger.
These fistulas are treatable but stubborn. Surgery is the standard approach, and most people return to work within one to two weeks afterward. Full healing, however, takes several weeks to several months depending on the size and complexity of the fistula. Recurrence is a real concern: studies put the rate somewhere between 5% and 50%, depending on the surgical technique used. Simpler procedures like fistulotomy (where the tunnel is laid open to heal from the inside out) tend to have lower recurrence rates, while more tissue-sparing techniques like LIFT procedures or biologic plugs carry recurrence rates of 50% or higher. The tradeoff is that gentler procedures are less likely to affect bowel control.
Fistulas in Crohn’s Disease
If you have Crohn’s disease, fistulas become dramatically more common. Up to 50% of Crohn’s patients develop a fistula within 20 years of their initial diagnosis. These are typically perianal fistulas, meaning they form around the anus, though Crohn’s-related fistulas can also develop between loops of intestine, between the intestine and bladder, or between the intestine and skin.
Crohn’s-related fistulas are harder to treat than standard anal fistulas because the underlying inflammatory bowel disease keeps driving tissue damage. Treatment usually involves a combination of medications to control inflammation and surgical procedures to manage the fistula itself. For many Crohn’s patients, fistulas become a recurring challenge rather than a one-time problem.
Obstetric Fistulas
Obstetric fistulas are a different story entirely, both in cause and in who they affect. These form when prolonged, obstructed labor damages the tissue between the vagina and bladder or rectum, creating a permanent opening that causes continuous leaking of urine or stool. Between 50,000 and 100,000 women develop an obstetric fistula each year worldwide, according to the World Health Organization. More than 2 million women in Asia and sub-Saharan Africa are currently living with an untreated obstetric fistula.
Obstetric fistulas are almost entirely preventable with access to timely cesarean delivery during obstructed labor. They’re extremely rare in high-income countries. In regions with limited access to emergency obstetric care, though, they remain a devastating and common complication, often affecting young women during their first pregnancy. Beyond the physical symptoms, untreated obstetric fistulas frequently lead to social isolation, as the constant leaking carries stigma in many communities.
Surgically Created Fistulas for Dialysis
Not all fistulas are unwanted. An arteriovenous (AV) fistula is a surgically created connection between an artery and a vein, typically in the arm, that provides reliable access for hemodialysis. For people with kidney failure who need regular dialysis, an AV fistula is considered the gold standard because it lasts longer and causes fewer infections than other access methods.
In the United States, AV fistula use among long-term dialysis patients rose from 32% in 2003 to 65% in 2014, reflecting a major push in nephrology to move patients away from catheters. Despite that progress, about 80% of people starting dialysis for the first time still begin with a catheter, often because an AV fistula needs weeks to months to mature before it can be used. Only about a quarter of new dialysis patients already have a fistula or graft maturing when they start treatment.
Congenital Fistulas
Some fistulas are present at birth. The most well-known congenital type is a tracheoesophageal fistula, an abnormal connection between the windpipe and the esophagus that occurs in about 1 out of every 3,000 to 5,000 live births. This condition almost always occurs alongside esophageal atresia, where the esophagus doesn’t fully form, and requires surgical repair shortly after birth. While rare in absolute numbers, it’s one of the more common congenital abnormalities that requires immediate neonatal surgery.
Who Is Most at Risk
Your risk of developing a fistula depends on several factors. For anal fistulas, men between 20 and 40 are the most commonly affected group. Having Crohn’s disease is the single biggest risk factor for any type of intestinal or perianal fistula. A history of anal abscess, radiation therapy to the pelvis, or previous surgery in the area also raises the likelihood.
For obstetric fistulas, the primary risk factors are giving birth very young (before the pelvis is fully developed), prolonged labor without medical intervention, and lack of access to skilled birth attendants. Geography matters enormously: a woman giving birth in rural sub-Saharan Africa faces a risk that is effectively zero for women delivering in well-equipped hospitals.
Overall, fistulas as a category are not rare. Between the millions of women living with obstetric fistulas, the tens of thousands of new anal fistula cases diagnosed annually in any given country, and the high rates among Crohn’s patients, fistulas represent a significant and often underrecognized health burden across very different populations.