Generally, a fistula is an abnormal connection or passageway between organs or vessels that normally do not connect. Fistulae can develop in various parts of the body. For example, types of fistulae, named for the areas of the body in which they occur, include anorectal fistula or fistula-in-ano or fecal fistula (between the rectum or other anorectal area and the skin surface), arteriovenous fistula or A-V fistula (between an artery and vein), biliary fistula (between the bile ducts to the skin surface, often caused by gallbladder surgery), cervical fistula (abnormal opening in the cervix), craniosinus fistula (between the intracranial space and a paranasal sinus), enteroenteral fistula (between two parts of the intestine), enterocutaneous fistula (between the intestine and the skin surface, namely from the duodenum or the jejunum or the ileum), enterovaginal fistula (between the intestine and the vagina), gastric fistula (between the stomach to the skin surface), metroperitoneal fistula (between the uterus and peritoneal cavity), perilymph fistula (a tear between the membranes between the middle and inner ears), pulmonary arteriovenous fistula (between an artery and vein of the lungs, resulting in shunting of blood), rectovaginal fistula (between the rectum and the vagina), umbilical fistula (between the umbilicus and gut), tracheoesophageal fistula (between the breathing and the feeding tubes) and vesicovaginal fistula (between the bladder and the vagina). Causes of fistulae include trauma, complications from medical treatment and disease.
Treatment for fistulae varies depending on the cause and extent of the fistula, but generally involves surgical intervention. Various surgical procedures are commonly used, most commonly fistulotomy, placement of a seton (a cord that is passed through the path of the fistula to keep it open for draining), or an endorectal flap procedure (where healthy tissue is pulled over the internal side of the fistula to keep feces or other material from reinfecting the channel). Surgery for anorectal fistulae is not without side effects, including recurrence, reinfection, and incontinence.
Inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis, are the leading causes of anorectal, enteroenteral, and enterocutaneous fistulae. The reported incidence of fistula in Crohn's disease ranges from 17% to 50%. Management of fistulae in patients with Crohn's disease continues to present an extremely challenging problem since many such fistulae do not respond to available treatments. Such fistulae and their recurrence are a very distressing complication that significantly reduces the quality of life of affected patients. Recent improvements in medical treatment (e.g., treatment with Infliximab) and expert surgical management have decreased the need for complicated surgery. However, many patients are not cured. Failure of fistulae to heal is probably due to the suboptimal quality of tissues that have been affected by Crohn's disease. Indeed, Crohn's fistulae provide a model system for wound healing under some of the worst possible conditions.
Another leading cause of fistulae is trauma, e.g. by rape, or by injuries sustained during childbirth, to the tissues of the vagina and the bladder and/or rectum leading to rectovaginal fistula and vesicovaginal fistula. Every year approximately 100,000 women across the developing world sustain such fistulae (also known as obstetric fistulae) during obstructed labor. During obstructed labor, the pressure of the baby's head against the mother's pelvis cuts off blood supply to delicate tissues in the region. The dead tissue falls away and the woman is left with a vesicovaginal fistula and sometimes a rectovaginal fistula. This hole results in permanent incontinence of urine and/or feces. The United Nations Population Fund (UNFPA) estimates the world's population of obstetric fistula sufferers at more than two million. This calculation could be a significant underestimate. Success rates for primary surgical repair range from 88 to 93 percent but decrease with successive attempts. Thus, a significant percentage of women have obstetrical fistulae that cannot be repaired surgically.
New therapies for fistulae are needed.