A colostomy is a surgical

Surgery

Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...

 procedure in which a stoma

Stoma (medicine)

A stoma is an opening , either natural or surgically created, which connects a portion of the body cavity to the outside environment...

 is formed by drawing the healthy end of the large intestine

Large intestine

The large intestine is the third-to-last part of the digestive system — — in vertebrate animals. Its function is to absorb water from the remaining indigestible food matter, and then to pass useless waste material from the body...

 or colon

Colon (anatomy)

The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...

 through an incision in the anterior abdominal wall and suturing it into place. This opening, in conjunction with the attached stoma appliance

Ostomy pouching system

An ostomy pouching system is a medical device prosthetic that provides a means for the collection of waste from a surgically diverted biological system and the creation of a stoma...

, provides an alternative channel for feces

Feces

Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...

 to leave the body. It may be reversible or irreversible depending on the circumstances.
There are many reasons for this procedure.