A vaginal fistula is an abnormal passage that forms between the vagina and another organ located nearby in the pelvic area. This unwanted connection creates a tract where bodily fluids, such as urine or stool, can leak into the vagina, leading to chronic irritation and infection. The type of fistula is named for the organs it connects, such as a vesicovaginal fistula linking the bladder and vagina, or a rectovaginal fistula connecting the rectum and vagina.
Injuries Stemming from Childbirth
Childbirth remains the most significant cause of vaginal fistulas globally, particularly in areas with limited access to emergency obstetric care. This type of injury, known as an obstetric fistula, results from prolonged or obstructed labor, where the baby’s head cannot pass through the mother’s pelvis. The mechanical obstruction causes the fetal head to press intensely against the soft tissues of the vagina and adjacent organs, such as the bladder or rectum.
This prolonged pressure clamps the blood vessels supplying the tissue, leading to ischemia, or lack of blood flow. Without oxygen, the compressed tissue dies, a process known as necrosis. Days after delivery, the dead tissue sloughs off, leaving behind a hole between the vagina and the urinary or digestive tract.
The formation of the fistula is not immediate but occurs as the damaged tissue breaks down, often becoming noticeable three to ten days after the delivery. In many cases of unrelieved obstructed labor, the baby does not survive, and the mother is left with a debilitating injury.
Accidental Damage During Pelvic Surgery
In developed nations, the most common cause of a vaginal fistula is an iatrogenic injury, meaning it is an unintentional complication arising during a planned surgical procedure. This often occurs during complex pelvic operations where the bladder or rectum lies close to the surgical site. A hysterectomy is the procedure most frequently associated with the development of a vesicovaginal fistula.
Other common procedures that carry a risk include Cesarean sections, complex colorectal surgeries, and operations involving the lower urinary tract. The fistula can form immediately if the bladder or bowel is accidentally cut or improperly sutured. Alternatively, the injury may be caused by a ligature or suture that traps adjacent tissue, which loses blood supply and necroses over time.
A post-operative infection at the surgical site can also weaken the repaired tissue, leading to the formation of an abnormal tract. These surgically induced fistulas occur in otherwise healthy tissue due to focal trauma. Many iatrogenic fistulas become symptomatic within days or weeks of the operation.
Erosion Caused by Inflammatory Bowel Disease and Infections
Chronic diseases that cause deep inflammation can lead to tissue erosion and the spontaneous formation of a vaginal fistula. Crohn’s disease, a type of inflammatory bowel disease (IBD), is the primary non-traumatic cause of rectovaginal fistulas. The chronic inflammation characteristic of Crohn’s can penetrate all layers of the intestinal wall, causing deep ulcerations.
These ulcers can tunnel through the weakened tissue to connect the rectum or small intestine to the vagina. The inflammation actively forms a persistent, tunnel-like tract. Up to half of people with Crohn’s disease may develop a fistula, although only a fraction of these are rectovaginal.
Other infectious processes, such as severe diverticulitis or a pelvic abscess, can also cause a fistula if the infection breaks through the vaginal wall. The localized collection of pus or severe inflammation erodes the barrier between the organs. Once the abscess ruptures into the vagina, a persistent passageway may remain, allowing bowel contents to leak.
Tissue Breakdown Following Radiation Treatment
High-dose radiation therapy, commonly used to treat pelvic cancers such as cervical, uterine, or rectal cancer, can damage healthy tissues surrounding the tumor. This intervention is a known cause of vaginal fistulas, particularly the rectovaginal type. The mechanism involves radiation-induced injury, which progressively damages the small blood vessels in the radiated area.
This damage leads to radiation necrosis, where the blood supply to the vagina and adjacent organs is significantly reduced. The affected tissue becomes fragile, poorly oxygenated, and unable to heal naturally. Months or even years after cancer treatment, this compromised tissue can break down, forming a fistula.
The development of a radiation-induced fistula is a delayed complication, often presenting around 20 months after the initial treatment. In some instances, the cancer itself can erode into the vaginal wall, or the combination of tumor invasion and radiation damage accelerates tissue breakdown. These fistulas are often complex due to the poor quality of the surrounding radiated tissue.