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How is Crohn’s disease different from ulcerative colitis?

Kathleen Blanchard's picture
Specialized cells found with Crohn's disease

Crohn’s disease is a type of inflammatory bowel disorder that can affect any part of the gastrointestinal tract; even the mouth. But how does your doctor diagnose Crohn’s disease that can also mimic ulcerative colitis and GI infections? Crohn's disease and ulcerative colitis symptoms have some similar characteristics.


The first step your doctor will take is to speak with you and find out your symptoms. What types of food cause pain? How long has the pain been present? What kind of diet and lifestyle factors might be involved? For instance, do you smoke, drink a lot of coffee, eat spicy foods or take any regular medications, even over-the-counter or herbs and supplements? Your doctor will also want to know if you have been on any recent antibiotics and discuss your bowel movement patterns.

Physical exam

There is no one single test for Crohn’s disease, so your doctor will also want to feel your stomach and do some basic blood work to find out if you’re deficient in any nutrients, electrolytes like potassium, magnesium or calcium. A complete blood count can detect anemia, elevated white blood cell count and more. But it’s important to understand most blood tests that are being done are non-specific and only act as a basis for ordering more studies, which can be frustrating.

It is also important to submit a stool specimen so your doctor can send it for testing that might detect parasites, infection or hidden blood in the bowels.


Your doctor should check you from head to toe, looking for rashes, ulcers in the mouth or any signs of fissures or fistulas in the anal area that can be signs of Crohn’s disease.

Crohn’s disease versus ulcerative colitis

Crohn’s disease and ulcerative colitis look different in the intestines. A colonoscopy and/or endoscopy might be ordered by your doctor to allow a direct look at the inflammation that is present.

Ulcerative colitis, like Crohn’s disease, causes ulcers in the intestines. Unlike Crohn’s disease, ulcerative colitis inflammation does not extend to the inner lining of the intestine.

Colitis often causes pain in the left lower quadrant. Crohn’s disease discomfort and pain is more often on the right side.

Both diseases are linked to gene variances, but more gene mutations are found with Crohn’s disease than colitis.

Visual exam of the colon shows a patchy thick appearance of the mucous lining with Crohn’s disease. With ulcerative colitis the lining is thinner and inflammation is more continuous.

Crohn’s disease and ulcerative colitis are both considered autoimmune disorders that may stem from the same genetic factors, though researchers are still unclear about what causes either of the diseases.

Both of the diseases appear to be triggered by overly aggressive immune fighting T-cells that attack gut bacteria. There a a variety of genes implicated that cause ulcerative colitis and Crohn’s disease. Both conditions cause chronic inflammation, can relapse and are triggered by various environmental factors that destroy the protective mucous layer of the gastrointestinal tract.

Ulcerative colitis and Crohn’s disease are both referred to as inflammatory bowel disease (IBD).

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How genes influence inflammatory bowel disease

The first gene abnormality associated with Crohn’s disease was CARD15. There are three separate variances of the gene that appear to make people susceptible to the condition.

One mutation, at least, is found in 25 to 35 percent of people with Crohn’s disease that affects the way the body recognizes bacteria.

The CARD15 gene abnormality affects people of European ancestry and is linked mostly to distal ileal Crohn's disease (the lower part of the intestine). The mutation also causes several other genes to act inappropriately. The end result, through a cascade of events, is that proteins in the epithelial cells lose integrity.

Another gene linked to both Crohn’s disease and ulcerative colitis that has been confirmed is DLG5 that is important for maintaining integrity of the epithelial cells in the colon.

To date, four gene variants are linked to Crohn’s disease in studies that have been replicated, and one gene is linked to ulcerative colitis.

In summary, the gene variations affect how the mucosal layer of the intestine functions, the immune response and killing of bacteria, which is why Crohn’s disease responds to probiotics and antibiotics.

A study published October, 2013 found specialized cells may be responsible for the inflammation caused by Crohn’s disease.

The finding came from researchers at University of Cambridge that suggested some, but not all cases of Crohn’s disease might come from a specialized type of intestinal cell called Paneth cells that had been found in the past, also associated with Crohn’s disease inflammation.

The destruction of intestinal cells associated with Crohn’s disease just might be a protective mechanisms, the study suggested, in an effort to keep misfolded proteins (that misbehave from genes) from doing damage.

The scientists suggest it is an interaction of genes, combined with ER stress - the response of the unfolded protein - that causes Crohn’s inflammation.

As a result of the finding, the researchers suggested the drug rapamycin that causes proteins to degrade might be a promising treatment for Crohn’s disease for treating the type that affects the small intestine.

The disease usually happens early in life, is incurable and believed to occur in those who are genetically susceptible when they are faced with unidentified environmental factors that continue to be explored - everyone’s condition is different and each individual experiences flare-ups from different lifestyle factors that even they may not be able to pinpoint.

Crohn's disease and ulcerative colitis both seem to share the same pathways that lead to pain, inflammation and other symptoms of IBD.

Diet, smoking, perhaps stress and infection can all trigger inflammation related to Crohn’s disease and ulcerative colitis. Researchers believe both conditions are brought about by a variety of complex factors that may begin with genetic predisposition and triggered by other external factors that they are continuing to explore. Interestingly, and another difference between the two, is that smoking (from the nicotine) seems to have a protective effect for people with ulcerative colitis but is harmful for Crohn's disease.

Columbia, St. Mary's
Medscape: Pathogenesis of Crohn's Disease
University of Cambridge

Image: "Micrograph of intestinal crypts with Paneth cells at the crypt bottom"
Credit: Professor Arthur Kaser
University of Cambridge

Related: How to cope with Crohn's disease