Fistula

n. narrow passage, opening (Medicine)

In medicine, a fistula (pl. fistulas or fistulae) is an abnormal connection or passageway between two epithelium-lined organs or vessels that normally do not connect. It is a very serious and painful disorder.
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A Fistula is a permanent abnormal passageway between two organs in the body or between an organ and the exterior of the body. [more]Fistula - Community and Resources

Noun
1. a chronic inflammation of the withers of a horse
(synonym) fistulous withers
(hypernym) animal disease
2. an abnormal passage leading from a suppurating cavity to the body surface
(synonym) sinus
(hypernym) passage, passageway

n. fistula, narrow passage, opening (Medicine)