Where actually is... m.crohn?

My dear patients !

Today I will write on presumed “basics” (with emphasis to “presumed” since I do not believe in „basics“ when it comes to IBD. In Crohn`s disease even less than in ulcerative colitis).

You might start to recognize that I do not write articles in a certain order based on eachother. I write what comes to my mind spontaneously on Monday morning on the train, because that’s where I write most of the time.

The question “where does Crohn`s disease occur ?” will be answered in 2 parts. First : “where” ? And second: “where else” ? (This “where else” …there is so much to say about. I often recognize that even patients with a long lasting course of disease do not know that Crohn`s disease can affect other  organs.)

Even though Crohn`s disease is known as an inflammatory bowel disease, it can occur in all parts of the digestive tract. Which means:

From the oral mucosa (very rare, not always easy to recognize, there are some other diseases or illnesses that should be excluded)

to the esophagus (rare)

the stomach (also rare)

the small intestine (not rare at all ! Frequent ! Almost half of the patients with Crohn`s disease according to literature, felt even more. Mostly the distant part of the small intestine at the junction to the large intestine is affected: the so called terminal ileum. (You might try to remember the term, you will hear and read it quite frequently)

and – last not least – the large intestine (not rare at all either, about 25% of patient with Crohn`s disease).

All parts of the digestive tract can be affected. All of them, from top to bottom.

A short explanation

In about half of the patients with Crohn`s disease the disease occurs in the small and large intestine. Mostly at the junction (the so called “ileocecal region“. Ileum is the distant part of the small intestine, where in the very end the “terminal ileum” is located. Cecum is the first section of the large intestine. Ileocecal region is the junction between small and large intestine).

That is the most common localization, that`s why “bowel disease” fits very well after all.

Let me ask a short question here : is it ok for you when I try to explain some medical terms ? It`s just that I recognize that even myself I start falling back to a specialist jargon sometimes while talking to my patients. I see their eyes get wider and wider (and the question marks in them bigger and bigger) and then recognize the deviation and go back to a more comprehensible language. But probably not every doctor does that and I thought, it is your advantage , when you become familiar with some important and frequently used medical terms. What do you think about that ? Is it ok or is it annoying ? Please give your Feedback in the Members Area.  

The small intestine is a part of the bowel where we as doctors at onset of the disease and every once in a while during the course of the disease may pay some focused attention to. Of course while performing endoscopy, but make no mistake: major parts of the small intestine we just do not reach with normal endoscopy. So if there is suspicion that Crohn`s disease might be located for example in the middle of the small intestine, one should consider different examination techniques like MRI or  – at given circumstances – capsule endoscopy. The „given circumstances“ are quite important especially for you as a patient with Crohn`s disease.

What else?

Does it make a difference, where in the digestive tract Crohn`s disease occurs ? Wether  it is located only in the terminal ileum or in the large intestine as well ? Does that affect the prognosis of the disease ? That question is actually a bit beyond the initial question (“where” ?) , but I suppose that is what you as a patient ask yourself and what you want to know.

Well, the prognosis is not determined only by the localization of the disease. It would not be helpfull to discuss a number of possible situations and individual cases here, that would rather

confuse and unsettle you. But let me tell you that it depends rather on the “how” of the inflammation (how much inflammation is there ?) than on the “where”.

What else can be said, on “where does Crohn`s disease occur” ?

One or more segments of the digestive tract can be involved. And it is typicall for Crohn`s disease, that in between the inflamed regions there are segments of not inflamed tissue.

 And this alternating inflamed and not inflamed tissue is what we are looking for while performing endoskopy (I also wrote about that in another episode (article 3).

Crohn`s disease can occur in a shorter or a longer segment of the digestive tract.

Or in a long segment and various short segments.

Or the other way: one short segments and different long segments  

Or in different short segments.

Or in different long segments.

The reason I write that a little laboriously : That is an important  difference between Crohn`s disease and ulcerative colitis, thats where they differ.

And why some patients just show a light inflammation at one site of the intestine and others show heavy inflammation in different parts of the intestine maybe developing fistulas (very important topic for Crohn`s disease, I will write about that seperatly) we – to be quite honest – just do not know.

Can the location of Crohn`s disease in the bowel change over the years ? Yes, that is possible. Yet it`s rare that the pattern of inflammation changes rapidly or very often. I do not have any statistics on that, but most of the patients have kind of a stable pattern of disease.

One kind of exeption : when Crohn`s disease occurs in the small intestine, we might expect that it occurs there in another segment. It is often observed that under therapy or even after a longer remission or after surgery the inflammation does occur at another site of the small intestine.  

What do you recognize?

And what do you as a patient recognize with respect to the “where” of Crohn`s disease.

That varies a lot.

You might recognize even small leasions in the oral mucosa immediatly. Esophagus and stomach – can be difficult. And even when there is a short (lets say < 10 cm) segment affected in the small intestine, especially at the site of terminal ileum you might not have any discomfort. I actually do know quite some patients who in that situation are completely free of symptoms. Again it more depends on the „how“ (how much inflammation is there) than on the „where“ (where ist the inflammation localized), wether you have symptoms or not.

But let me tell you right away: we should do therapy anyhow. Inflammation leads to swollen mucosa. Inflammation on top of inflammation on top of inflammation (remember the vicious circle ?) leads to appearance of scare. And swollen mucosa as well as scare lead to constriction (“stenosis”, another term you might have heard before). And stenosis – or constriction – of the bowel will surely result in symptoms, that`s for sure !

And because there might be relevant inflammation without you recognizing it, it is important to perform endoskopy (or other diagnostics) every once in a while. And it is also important that in case you recognize some change in symptoms even after a longer remission or under therapy  or after surgery you tell your doctor about it.


That much for today on behalf of “where” of Crohn`s disease.

Again : take care and best regards  !

Dr. med. Susanne Weyrauch


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