A fistulotomy is the surgical opening 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 in a seton; a cord passed through the tract in a loop that is slowly tightened over a period of days or weeks. A fistulotomy is the surgical opening 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 in a seton; a cord passed through the tract in a loop that is slowly tightened over a period of days or weeks.