is the surgical opening or removal of a fistulous
tract. They can be performed by excision of the tract and surrounding tissue, simple division of the tract, or gradual division and assisted drainage of the tract by means of a seton
; a cord passed through the tract in a loop which is slowly tightened over a period of days or weeks.
Fistulas can occur in various areas of the human body, and the location of the fistula influences the necessity of the procedure. Some, such as ano-vaginal and perianal fistulas are chronic conditions, and will never heal without surgical intervention.