Fistula in Ano is a fistulous opening into the gut, which is extremely difficult to heal, on account of the action of the muscle which keeps the extremity of the gut closed, and also from the passage into it of fecal matter from the bowel. The knife of the surgeon is here necessary; as no other means are of any avail.

Fistula in Perineo signifies an opening from the perineum into the urethra, through which the urine dribbles when the patient makes water. Sometimes there is a blind fistula in perineo; that is, a small narrow fistula, opening into the urethra, but not externally. Sometimes a fistulous communication forms between the urinary passage and the bowel, which may be known by air passing through the urethra.

All of these disorders require the active interference of the surgeon.