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What Is a Colostomy?

A colostomy is an opening in the belly (abdominal wall) that’s made during surgery. It's usually needed because a problem is causing the colon to not work properly, or a disease is affecting a part of the colon and it needs to be removed. The end of the colon (large intestine) is brought through this opening in the skin to form a stoma. A colostomy might only be needed for a short time (temporary), maybe for 3 to 6 months. A temporary colostomy may be used when a part of the colon needs time to rest and heal from a problem or disease. But sometimes a disease, such as cancer, is more serious and a colostomy may be needed for the rest of a person's life (permanent).

Where the colostomy stoma will be on the abdomen depends on which part of the colon is affected. Some colostomies are large, some small; some are on the left side of the abdomen, some are on the right, others may be in the middle. A Wound Ostomy Continence nurse (WOCN or WOC nurse) or the surgeon will figure out the best location for your stoma. (A WOC nurse is a specially-trained registered nurse who takes care of and teaches ostomy patients. This nurse may also be called an ostomy nurse.)

When you look at a stoma, you are actually looking at the lining (the mucosa) of the intestine, which looks a lot like the inside lining of your cheek. The stoma will look pink to red. It’s warm and moist and secretes small amounts of mucus.

The way the stoma looks depends on the type of colostomy the surgeon makes and on individual body differences. It may look quite large at first, but will shrink to its final size about 6 to 8 weeks after surgery. The shape will be round to oval. Some stomas may stick out a little, while others are flat against the skin.

Unlike the anus, the stoma has no valve or shut-off muscle. This means you won’t be able to control stool passing from the stoma, but sometimes bowel movements can be managed in other ways. There are no nerve endings in the stoma, so the stoma itself is not a source of pain or discomfort.

What does a colostomy do?

A colostomy changes the way your body works to allow stool to pass. After a colostomy has been created, the intestines will work just like they did before except:

  • The colon and rectum beyond the colostomy are disconnected or removed.
  • The anus is no longer the exit for stool, but it will still pass mucus from time to time. This is normal.

Since nutrients are absorbed in the small intestine, a colostomy does not change how the body uses food. The main functions of the colon are to absorb water, move the stool toward the anus, and then store stool in the rectum until it’s passed out of the body. When a colostomy changes the stool’s route, the storage area is no longer available.

The higher up in the colon the colostomy is made, the shorter the colon is. A shorter colon means it has less time to absorb water, making the stool softer or more liquid. A colostomy further down in the colon, near the rectum, will put out stool that has been in the intestine a longer time. Depending on the effects of illness, medicines, or other forms of treatment, the longer colon can put out a more solid or formed stool. Some people with colostomies find that they are able to pass this stool at certain times of the day with or without the help of irrigation. (See Caring for a Colostomy.)

After surgery, some people still may feel urges and even have some discharge from the anus. This discharge is mucus, blood, and at times stool, left from the operation. If the rectum remains after surgery, it will keep putting out mucus that can be passed harmlessly whenever you have the urge.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.

In its original form this document was written by the United Ostomy Association of America (1962-2019). It has since been modified and updated by the American Cancer Society using the following sources.

Berti-Hearn L, Elliott B. Colostomy care: A guide for home care clinicians. Home Healthcare Now. 2019; 37(2):68-78. Accessed at on October 2, 2019.

Hollister. Types of ostomies. Accessed at on October 2, 2019.

Hollister. Understanding your colostomy. Accessed at on October 2, 2019.

United Ostomy Association of America (UOAA). Colostomy guide. Accessed at on October 2, 2019.

United Ostomy Association of America (UOAA). New ostomy patient guide: Colostomy, ileostomy, urostomy, continent diversion. Accessed at on October 2, 2019.

Last Revised: October 2, 2019

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