Lumen and the Intestines

The lumen is inside the intestine and it's important to keep it clear

Small Intestinal Wall
The wall of the small intestine is composed of several parts, with the interior being called the lumen. PIXOLOGICSTUDIO/Science Photo Library/Getty Images

The lumen is the opening inside a tubular body structure that is surrounded by body tissue known as an epithelial membrane. Examples of body structures that have a lumen include the large intestine, small intestine, veins, and arteries. The name comes from the Latin "lūmen," one meaning of which is "light." This is probably because the lumen is an opening inside a tube, and light will pass through a tube.

The size of the lumen in the intestine might be measured in order to determine if the intestinal walls are thickening. When the walls of the intestine thicken and cause the lumen to become narrower, it can lead to problems such as strictures (narrowed parts of the intestine).

Intestinal Lumen

In the intestines, the lumen is the opening inside the bowels and is surrounded by the other parts of the intestinal wall: the mucosa, the submucosa, the muscularis, and the serosa.  

In order for food to pass through the intestines, the lumen must be clear, open, and free from any structural problems that can cause an obstruction. In people with inflammatory bowel disease (IBD), the lumen might be affected. IBD goes through periods of active disease and remission. In times of active disease, there is inflammation that affects the mucosal layer of the intestine, which can cause ulcers. As the disease is managed and the ulcers on the inner intestinal wall heal over in places, scar tissue may form. The repeated cycle of inflammation and healing can build up the scar tissue to the point where it actually results in a thickening of the wall of the bowel.

When the Lumen Becomes Narrowed

Scar tissue is not as flexible as regular tissue and therefore it behaves differently. When there is scar tissue in the intestine, the lumen becomes affected, and it may become narrowed or obstructed (blocked). The narrowed part of the lumen is called a stricture. The waste material can't pass through the lumen easily, which can lead to pain, bowel obstructions, or other complications.

Strictures tend to be more commonly associated with Crohn's disease than with ulcerative colitis, however, they can occur in both forms of IBD. The reason for this is that Crohn's disease can occur anywhere in the digestive tract from the mouth to the anus, and can affect several layers of the bowel wall. Ulcerative colitis usually affects only the large intestine and the rectum, and the inflammation it causes is generally confined to the inner mucosal layer. In Crohn's disease, strictures tend to be in the small intestine, and in ulcerative colitis, strictures tend to be in the rectum.

Strictures can be very troublesome for people with IBD because they block food from moving through the bowels. With strictures that are very narrow, food begins to back up in the bowel. This could lead to a bowel obstruction, and there could be symptoms of pain, vomiting, diarrhea, or constipation. In some cases, obstructions can be treated in the hospital with a nasogastric (NG) tube and other methods, but some strictures are advanced enough that they require surgery. Without surgery, the obstructions might just keep occurring.

Pronunciation: lū′men

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