A colostomy is an opening in the large intestine, or the surgical procedure that creates one. The opening is formed by drawing the healthy end of the colon through an incision in the anterior abdominal wall and suturing it into place. This opening, often in conjunction with an attached ostomy system, provides an alternative channel for feces to leave the body. Thus if the natural anus is not available for that job (for example, in cases where it has been removed in the fight against colorectal cancer or ulcerative colitis), an artificial anus takes over. It may be reversible or irreversible, depending on the circumstances.