Fistulas are abnormal connections between different tissues or organs in the body. Fistulas usually occur as a result of surgery or injury, according to MedlinePlus, an online medical encyclopedia sponsored by the U.S. National Library of Medicine. They can also occur at birth as a birth defect. The various types of fistulas are categorized based upon the organs or tissues involved in the abnormal connection.
Arteriovenous Fistula
This type of fistula involves an abnormal connection between an artery and a vein. The separation between arteries and veins proves important because arteries carry oxygen- and nutrient-rich blood to the tissues, and veins carry blood that needs to become oxygenated back to the lungs. However, the Mayo Clinic website, MayoClinic.com reports that an arteriovenous fistula results in a short-circuiting of this process: blood flows directly from an artery into a vein, without the necessary stop to replenish tissues with nutrients and oxygen. Thus, the tissues down-stream of the fistula receives less blood then they optimally need, which can result in tissue damage. The most common place for arteriovenous fistulas, states MayoClinic.com, remains the legs; however, they can occur in arms, lungs, or brain as well. Some babies are born with arteriovenous fistulas, and some develop in people after injury or surgery.
Anorectal Fistula
An anorectal fistula is an abnormal connection between the anus or rectum and another nearby tissue. The second tissue involved in the connection is often the skin, but is sometimes the vagina in women, according to the online medical library Merck Manuals. Merck Manuals also states that this type of fistula commonly occurs in people with Crohn's disease, who have high levels of chronic inflammation in the digestive tract. The constant injury to and healing of the anorectal tissue can result in the formation of an anorectal fistula. They can also develop in people who have anorectal abscesses. This type of fistula can cause pain and produce pus.
Tracheoesophageal Fistula
In a tracheoesophageal fistula, the abnormal connection forms between the esophagus, the tube that connects the mouth and the stomach, and the trachea or "windpipe," which connects the mouth and sinuses to the lungs. These tubes are both located in the throat, residing parallel to one another. Because of the abnormal connection during a tracheoesophageal fistula, swallowing can cause liquids or foods to become diverted into the lungs instead of the stomach. A tracheoesophageal fistula is a birth defect that develops while the baby remains in the mother's uterus. It occurs in about one in 3000 to 5000 live births, according to the Weil Medical College of Cornell University, and has associations with other types of birth defects. Physicians usually perform surgery to repair the fistula.
