What Is the Sigmoid Colon?

An endoscope is used to look inside the colon during a sigmoidoscopy.
The sigmoid colon is the end portion of the large intestine nearest the rectum.
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  • Written By: Dorothy Distefano
  • Edited By: Michelle Arevalo
  • Last Modified Date: 25 June 2014
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The sigmoid colon is the end portion of the large intestine, nearest the rectum. This portion of the intestine is in the form of an s-shaped loop, and is usually approximately 16 inches (40.64 cm) in length. It is able to expand and contract dependent upon the amount of fecal material being stored until it is ready to be evacuated from the body.

The colon is also known as the large intestine or bowel. The colon is comprised of the ascending, transverse, descending, and sigmoid colons, as well as the rectum and anus. The purposes of the colon are to eliminate toxins and wastes from the body, to absorb and transfer nutrients into the bloodstream, and to absorb fluids.

The colon is one long tube that begins at the end of the small intestine. The entire colon measures approximately 5 feet (1.5 m) long, much shorter than the typical 16 feet (4.8 m) of small intestine. It is composed of lymphatic and connective tissues, blood vessels, and muscles. The muscle tissue is responsible for the movement, or peristalsis, necessary to propel waste through the colon.

Most of the water is absorbed from feces as it moves through the ascending colon. The waste then moves on to the transverse colon, beginning at the hepatic flexure. This is the portion of the colon in which the waste is formed into stool. At the splenic flexure, the transverse colon becomes the descending colon, where stools become more solid.

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The s-shaped sigmoid colon begins at the end of the descending colon. Stools continue through the sigmoid colon, and may be stored in this area until they are moved into the rectum. The rectum is a short section of bowel that leads to the anus, where stool is expelled.

Since one of the most common causes of cancer death in the United States is colon cancer, many health professionals recommend a sigmoidoscopy for men and women over the age of 50. This procedure evaluates the sigmoid colon for polyps or other lesions. During the procedure, the doctor can visualize the inner lining of the sigmoid colon, remove polyps, and take tissue samples for biopsy.

As the sigmoid colon must increase pressure to move stool into the rectum, occasional bulging sacs called diverticuli may form. These small sacs, if infected, cause a condition known as diverticulitis, which may be accompanied by abdominal pain and fever. Diagnosis is generally made with a sigmoidoscopy. Treatment will likely include anti-spasmodic drugs and antibiotics.

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Discuss this Article

anon124757
Post 4

i have one 10mm polyp in the sigmoid colon, resected and retrieved. I am still in pain.

pleats
Post 3

My ex had a sigmoid colon ulcer -- talk about gross!

That is one condition that you really don't want to be around when it flares, let me tell you!

Definitely a disease to avoid if you have any means to do so.

LittleMan
Post 2

@CopperPipe -- I've read that most sigmoid colon blockages are actually caused by colon cancer.

I would assume your doctor would have told you if you were at risk for sigmoid colon cancer though.

Another common cause could be diverticulitis of the sigmoid colon.

This happens when the diverticula (basically small hernias) push out through the natural openings in your sigmoid colon. If this happens often then the colon can get narrower, which could lead to a blockage.

However, as far as I know diverticular disease in the sigmoid colon is pretty rare -- you should ask your doctor to elaborate so you can have a better idea of what you should do.

Hope this helps.

CopperPipe
Post 1

What can cause a sigmoid colon blockage? My doctor told me that I was at risk for them, and I'm just trying to get some more information to wrap my head around this.

Any information would be greatly appreciated!

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