Close-up of a 22 month old baby boy with a colostomy. A colostomy is a surgical procedure in which a stoma is formed by drawing the healthy end of the large intestine or colon through an incision in the anterior abdominal wall and suturing it into place. This opening, in conjunction with the attached stoma appliance, provides an alternative channel for faeces to leave the body. It may be reversible or irreversible depending on the circumstances.