UC causes: an inside look.

What causes ulcerative colitis (UC)? The exact answer is still unknown, but there are different potential causes. Let’s take a look at some of those below:

On this page, you’ll find info about:

It’s not you. It’s your immune system.

The immune system is complex—it’s made up of many different cells, tissues, and organs throughout the body. When working normally, the immune system fights off foreign substances it sees as harmful to protect the body from infections.

However, for people with ulcerative colitis, the immune system can activate even when there is no real threat. This reaction in the immune system can cause inflammation, which can become chronic and lead to:

  • Loose stool and diarrhea 
  • Mucus in the stool 
  • Ulceration, which may lead to bleeding in the stool 

It all starts with inflammation

The inflammation of ulcerative colitis impacts the colon lining but does not extend through the entire thickness of the bowel wall. It usually begins in the rectum and lower colon but may also spread continuously to involve the entire colon. 

UC locations

Click/tap on the interactive tool below to learn more about some possible areas where ulcerative colitis can be active.

Extensive Colitis (pancolitis)

This is when the entire colon is affected. Continuous inflammation begins at the rectum and extends beyond the splenic flexure.

Left-Sided Colitis

With left-sided colitis, continuous inflammation begins at the rectum and extends far into the colon.

Sigmoid Colon

Left-sided colitis can affect the lower segment of the colon located right above the rectum which is known as the sigmoid colon.

Ulcerative Proctitis

Here, bowel inflammation is limited to the rectum. This condition typically affects less than six inches of the rectum.

What are some UC complications?

UC patients can present with complications like ulcers. When this happens, inflammation often occurs in the rectum and may extend to involve additional parts of the colon. This can lead to ulcers that can be found in the inner lining of the large intestine. They vary in size and depth depending on disease severity.

There isn’t just one reason for UC

Not one factor alone is known to cause ulcerative colitis. However, there are thought to be a few factors that interact with one another and likely contribute to it:

Immune System Response

In people with inflammatory bowel disease, like ulcerative colitis, inflammation is the result of the immune system mistakenly attacking healthy tissue in the intestinal lining.

Genetics and Heredity

While genetics and heredity are not absolute predictors that the disease will occur, researchers have identified several genes that seem to make people more likely to develop the disease.

Environmental Factors

Things such as air pollution, medication, and dietary issues may trigger a harmful immune response in the intestines.

Next page:

On to UC Severity & Progression


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