And, how do we know that we are in remission, other than observing the symptoms? Is it based on calprotectin levels?
What kind of diet is recommended or is it based on individual reaction's to the specific food?
Remission in general means being free of disease or the disease is so low and quiet that your condition is pretty much the same as having no disease. There are several types or levels of remission depending on how the remission is assessed.
1. Clinical Remission - this is remission based on symptoms. If your symptoms of Crohn's have been abolished or reduced to a very low level, you are said to be in "clinical remission." This is what most patients are interested in achieving - to feel normal and healthy again.
2. Endoscopic Remission - Also called "mucosal healing." This is where there is no visible sign of ulcers or inflammation in the gut upon colonoscopy.. Your bowel looks normal, pink, and healthy. This is what most GIs are trying to achieve. Clinical remission and endoscopic remission do not always align. You could feel great again (especially sometimes after first starting steroids), but the doctor may still see a lot of trouble during colonoscopy. Thus the GI knows to keep adjusting the medication to find the right long-term solution even though the patient feels pretty good right now. And vice versa too. Your gut can sometimes look fine after treatment, but some of the symptoms have continued to linger - frustrating both patient and doctor.
3. Histologic Remission - This is the highest or strictest form of remission and the hardest to achieve. It means that not only are you in endoscopic remission but also the tissue specimens that were collected during the colonoscopy show no signs of inflammation when examined by a pathologist under a microscope. This is probably the closest to a true total remission.
4. Chemical Remission - This term isn't used all that often. It means that blood or stool inflammation markers such as CRP or fecal calprotectin have dropped to normal levels. It's not usually used as a stand-alone definition of remission but is more of an adjunct to the other forms of remission - sort of added proof that, for example, the endoscopic remission is looking pretty good because the markers are low. Or maybe the clinical remission might be coming to an end because the markers are starting to rise. Assessing this can be a handy way to routinely monitor the disease in between colonoscopies - just run a simple blood or stool test instead of having to do another colonoscopy every time.
In my own case I have for years been in remissions #1 and #4 but not quite in #2 or #3. I have basically no symptoms and and normal lab test results, and colonoscopy looks great for the entire large bowel, but the ileum of the small bowel still shows a little redness suggesting residual inflammation (no ulcers). And this low level inflammation has been confirmed by the histologic pathology reports. It's been this way for 5 years now - ever since I went on Stelara, and if it doesn't get any worse, I'm fine with it. My life feels normal enough that I would be happy to go the distance with this low level of disease.
One important note is that none
of these forms of remission constitutes a cure. Unfortunately, there currently is no cure for Crohn's disease. So it's perfectly possible for even the most complete and stable of remissions to come to an end and the patient suffer a flare.
As for your diet question. you hit it right when you said it's "based on individual reaction's to the specific food." In my case I haven't really seen where diet helps or hurts my disease much at all. For others it can be crucial - with nasty trigger food that can knock them out of remission and into a flare. And the trigger foods vary quite a bit from person to person.
One exception to what I just said about diet is EEN - a form a treatment where the patient eats only specialized formula and no solid food. This is useful for inducing remission, but is very hard to sustain long term. It is primarily used in children, since it is much easier to strictly control a small child's diet than it is the diet of a teenager or adult.