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an abnormal passage between hollow organs or between an organ, body cavity, or focus of disease and the body surface. Usually in the form of a narrow canal lined with epithelium or granulations, it continuously discharges pus, mucus, bile, urine, or feces.
Congenital fistulas, for example, umbilical fistulas, are developmental anomalies. Acquired fistulas result from such chronic inflammations as osteomyelitis, from tumors, or from injuries. Fistulas are usually treated by surgery.
It is sometimes necessary to create artificial fistulas surgically. They may connect hollow organs, in which case they are called internal fistulas, or anastomoses. An example is gastroenteroanastomosis in cicatricial stenosis of the outlet of the stomach.
Gastrostomy is the establishment of an external fistula, or stoma, for artificial feeding. External fistulas also permit the discharge of urine or feces. For example, cystostoma is a fistula of the urinary bladder formed when the urethra is compressed by a tumor. With external fistulas, care must be taken to avoid irritating or infecting the surrounding skin.