Respiratory Tract Fistula: An abnormal passage communicating between any component of the respiratory tract or between any part of the respiratory system and surrounding organs.Fistula: Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body.Respiratory Tract Infections: Invasion of the host RESPIRATORY SYSTEM by microorganisms, usually leading to pathological processes or diseases.Arteriovenous Fistula: An abnormal direct communication between an artery and a vein without passing through the CAPILLARIES. An A-V fistula usually leads to the formation of a dilated sac-like connection, arteriovenous aneurysm. The locations and size of the shunts determine the degree of effects on the cardiovascular functions such as BLOOD PRESSURE and HEART RATE.Intestinal Fistula: An abnormal anatomical passage between the INTESTINE, and another segment of the intestine or other organs. External intestinal fistula is connected to the SKIN (enterocutaneous fistula). Internal intestinal fistula can be connected to a number of organs, such as STOMACH (gastrocolic fistula), the BILIARY TRACT (cholecystoduodenal fistula), or the URINARY BLADDER of the URINARY TRACT (colovesical fistula). Risk factors include inflammatory processes, cancer, radiation treatment, and surgical misadventures (MEDICAL ERRORS).Cutaneous Fistula: An abnormal passage or communication leading from an internal organ to the surface of the body.Bronchial Fistula: An abnormal passage or communication between a bronchus and another part of the body.Vascular Fistula: An abnormal passage between two or more BLOOD VESSELS, between ARTERIES; VEINS; or between an artery and a vein.Rectal Fistula: An abnormal anatomical passage connecting the RECTUM to the outside, with an orifice at the site of drainage.Gastric Fistula: Abnormal passage communicating with the STOMACH.Urinary Fistula: An abnormal passage in any part of the URINARY TRACT between itself or with other organs.Esophageal Fistula: Abnormal passage communicating with the ESOPHAGUS. The most common type is TRACHEOESOPHAGEAL FISTULA between the esophagus and the TRACHEA.Biliary Fistula: Abnormal passage in any organ of the biliary tract or between biliary organs and other organs.Respiratory System: The tubular and cavernous organs and structures, by means of which pulmonary ventilation and gas exchange between ambient air and the blood are brought about.Pancreatic Fistula: Abnormal passage communicating with the PANCREAS.Rectovaginal Fistula: An abnormal anatomical passage between the RECTUM and the VAGINA.Vesicovaginal Fistula: An abnormal anatomical passage between the URINARY BLADDER and the VAGINA.Vaginal Fistula: An abnormal anatomical passage that connects the VAGINA to other organs, such as the bladder (VESICOVAGINAL FISTULA) or the rectum (RECTOVAGINAL FISTULA).Tracheoesophageal Fistula: Abnormal passage between the ESOPHAGUS and the TRACHEA, acquired or congenital, often associated with ESOPHAGEAL ATRESIA.Urinary Bladder Fistula: An abnormal passage in the URINARY BLADDER or between the bladder and any surrounding organ.Arterio-Arterial Fistula: Abnormal communication between two ARTERIES that may result from injury or occur as a congenital abnormality.Arteriovenous Shunt, Surgical: Surgical shunt allowing direct passage of blood from an artery to a vein. (From Dorland, 28th ed)