Where is.. ulcerative colitis?

My dear patients!

Lately I wrote about where in the intestine Crohn`s disease occurs. And I mentioned that I would not write in a certain order. Next thing was, that I really wanted to share my thoughts on the inspiring ECCO-Congress. But now having written about the “where” of Crohn`s disease I did not want to skip this important, basic issue on ulcerative colitis. It would really feel like trying to walk with two different shoes. Which is uncomfortable and makes  walking really kind of difficult.  So let me tell you something about the “where” of ulcerative colitis today.

As for Crohn`s disease the question “where else?” should and will be answered for ulcerative colitis as well. Just like in Crohn`s disease ulcerative colitis can also affect other organs. But this aspect is again very similar and in parts identical  for ulcerative colitis  and Crohn`s disease. So I think I will write on that in one article for both diseases.

But today : where does ulcerative colitis occur ? That is a lot easier to answer than for Crohn`s disease. Ulcerative colitis – as the name “colitis” suggests – occurs in the large intestine, the colon, as we call it. Colitis = inflammation of the colon. Simple as that.

Normaly ulcerative colitis occurs at the lower part of the large intestine (called “Rectum”). And from there it spreads in direction towards the small intestine (“upwarts”). In a continuous way.

The whole

… “in between the inflamed mucosa there are not inflamed sections” or

…”the inflammation can occur in dífferent shorter or longer parts of the whole intestinal tract” or

…”different sections of the whole gastrointestinal tract can be affected” just doesn`t exist for ulcerative colitis.

There is always just one affected area in the large intestine. The length may vary, but there is just one affected section in the colon (large intestine).

Only a few centimeters of the large intestine, starting in very distal part can be affected. Or a longer segment can be affected. Bit it always starts at the end of the colon (Rectum). And it always spreads from there in direction of the small intestine.

And depending on how much of the colon is affected we  are talking about either

proctitis” (when just the very few centimeters from the colon are affected) or

distal colitis” when the last segment of the colon, the rectum is affected. We talk about

rectosigmoiditis” (when the last 30-40 cm are effected) ,

left sided colitis” (as the name suggests when the left side of the colon is affected)

or an “extended colitis / pancolitis” (when the whole colon – or large intestine – is affected).

(I almost fell like I should apologize for all the medical terms. But that is the terminology. And I imagine you might hear these terms in the conversation with your doctor or read them in your medical reports – now you have the chance to know what they are about)

We make this distinction depending on what we see while performing endoscopy. When we have reached the upper edge of the inflamed region with the endoscope in the colonoscopy, we don`t have to look further for inflammed tissue. We don`t have to think about whether there might be some more inflammation somewhere in the small intestine either. 

Really simple as that?


Well…almost. There are some exceptions, but small ones. There are actually three of them. That does not change the basic principle that only the large intestine is affected, that there is always just one inflamed segment, and the inflammation always begins in the lower part of the large intestine (rectum).

  1. First exception is that we possibly find a small area (“patch”) at the coecum (first segment oft he large intestine) with inflamed musoca even though colitis occurs just at the end of the colon. It is called “coecal patch“.
  2. Second exception is that the last part of the small intestine, the terminal ileum might be affected. It`s called “backwash ileitis“, which is a very descritive term, since the colitis is slopping over to the last cm of the small intestine.
  3. And sometimes we see a “rectal sparing“. As the name suggests in that case you won`t find inflammation in the last segment oft he large intestine (rectum), which is about 15 cm. The rectum is spared from inflammation.

But these are exceptions, rare.

And something I want to pass on to you already: whether there is a backwash ileitis or a rectal sparing may be relevant for assessing the prognosis. Because there is prove, that patients with ulcerative colitis and backwash ileitis or rectal sparing are more likely to develop a certain accompanying illness involving the bile ducts. I will write about that separately.

And how about patterns of inflammation now? Does ulcerative colitis always spread in direction of the small intestine? Does it always spread until the whole colon is affected?

No. There are quite a few patients who deal with inflammation which occurs only on the last centimeters of the large intestine over years and decades.

And there are others who start of with proctitis and within a couple of months the colitis spreads over a large part of the colon, sometimes even under therapy. And the reason wether it turns out the one or the other way we don`t know.

What does that mean for you?

And what does the spread of the disease mean for you in your certain situation? Well, in case the whole colon is affected, in case of an extended colitis or pancolitis we generaly expect a more serious illness in comparsion to a proctitis or a rektosigmoiditis (please note: we expect does not mean: in a 100% it always turns out that…).

Yet the spread of the disease does not always correlate with the severeness of the disease. Sometimes half of the colon or more shows heavy infammation and after a couple of weeks with therapy and medication the inflammation is diminishing and shows a sustained stabilization. And on the other hand it is possible that just a few centimeters of inflammed mucosa at the end of the colon show heavy flares over the years and make treatment really sophisticated.

As it is often the case: there is no: „in case of…there is always“.

Every disease has a different course and every patient is different from another. (And please have that in mind when you talk to other IBD patients with ulcerative colitis or Crohn`s disease. The course of somebody elses disease has exactly nothing to do with your own)   

And that is basicly it on the “where” of ulcerative colitis: Actually occurs in the colon, inflammation in just one part of the large intestine. The three exceptions (coecal patch, rectal sparing and backwash ileitis) are …exeptions, which might give us a hint about the course of the disease.


Take care and best regards
Dr. Susanne Weyrauch


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