Fistulas

A fistula is an unnatural, narrow channel, leading from some natural cavity in the body to the surface, such as an opening of the interior of the bowels to the surface, or from the thyroid gland to the surface; or it may be a communication between two body cavities where none should exist, as for example a direct communication between the bladder and the bowel, as can happen to women from injury during protracted childbirth. Sometimes the defect is congenital, but usually the cause is either disease or injury. Often, the blockage of the duct of a gland leads to a fistula, as in the case of a salivary fistula which may form on the face so that the saliva then runs out on the cheek instead of in the mouth.