Most people associate Crohn’s disease with the symptoms that accompany it – pain, cramping, diarrhea, appetite loss, so on and so forth. What people don’t often realize is that the inflammation characteristic of Crohn’s disease can cause irreversible damage to the intestines over time. The bowel wall is thickened during inflammation, due to the many white blood cells and water (swelling) that enter the bowel wall during a flare. As the bowel heals after a flare, scar tissue, or fibrosis, is left behind.

Scar tissue, strictures and adhesions

In the majority of Crohn’s patients, scar tissue develops within the intestinal walls as part of the healing of Crohn’s-related inflammation. Over time, this scar tissue buildup can cause narrowing of the gastrointestinal (GI) passage, which subsequently slows the movement of food and stool throughout the GI tract. The segment of GI tract that becomes narrowed is called a stricture.

The stricture results from a thickened intestinal wall. It can be from inflammation and edema (initially) or it can be from accumulated scar tissue. It is hard to tell the difference on a CT scan or MRI.

Strictures (if narrow enough) can cause intense pain and vomiting, and if they progress (i.e. the narrowing worsens), the intestine can actually become fully blocked. When a blockage occurs, medical intervention – which may include surgery – is necessary.

And although the prospect of surgery is unpleasant (to say the least), it may be more common than you think. In fact, an estimated 70% of Crohn’s disease patients require some sort of surgical procedure to treat scar tissue buildup over the course of their disease.

While it may be prevalent, intestinal surgery comes with its own set of complications. Adhesions – or bands of scar tissue – may develop after an operation on (or trauma to) the GI tract. Adhesions run from the point of surgery to another part of the intestine (or another organ). For some people, these adhesions will be subtle, painless and self-correcting; for others they may twist or pull on the intestines, resulting in an obstructed GI passage. If this occurs, an additional surgery to treat the adhesive obstruction may be required.

We know that the Crohn’s disease course varies from individual to individual, but often times its progression evolves from inflammatory, to stricturing, to (worst case scenario) penetrating disease.

Abscesses and fistulas

Penetration is another aspect of Crohn’s disease that warrants further discussion. Because the inflammation associated with Crohn’s affects all layers of the intestinal wall, the wall may in turn become weak and susceptible to a wide range of structural issues. This intestinal weakness combined with scar tissue buildup (with subsequent narrowing of the GI tract and buildup of upstream pressure) may result in the formation of fistulas and abscesses.

Abscesses and fistulas occur when the inflammation penetrates through all layers of the digestive tract.

A narrow stricture results in high pressure upstream, and associated inflammation makes the intestinal wall weak. The combination of high pressure and a weakened wall allows the intestinal contents to penetrate the wall and relieve the built up pressure. When this penetration occurs, it often leaves behind a little passage or tunnel – this is called a fistula. In Crohn’s disease, fistulas may develop between a section of intestine and an outer organ (like the skin), an inner organ (like the bladder) or another part of the intestine.

Typically, fistulas occur where there are areas of high intestinal pressure combined with a weakened wall. High pressure occurs in strictures (and just upstream of strictures), or just upstream of the anal sphincter. Most patients with IBD develop really strong sphincters, because they have a lot of practice at holding in bowel movements. Given this tendency, many Crohn’s disease patients develop fistulas in and around the anus.

Among a variety of symptoms, anal fistulas can cause irritation of the skin around the anus, leakage of fluid or pus, and occasionally a leak of fecal matter. Treatment typically involves a combination of medication and surgery; the approach varies depending on severity of symptoms, fistula location and number/complexity of fistula tracts. Talk to your doctor immediately if you suspect you might have a fistula – earlier intervention is always preferred.

Abscesses are little pockets of infected fluid and pus that develop when the contents of the bowel leak through the intestinal wall but are walled off by your immune system before they can cause more harm. They can cause pain and discomfort, and while some drain on their own, many require medical intervention to drain the infected fluid.


What is it – exactly – that your healthcare team is monitoring? When they take a blood test, what are they looking for? When they request a stool sample, what are they looking for? When they do a computerized tomography (CT) scan or colonoscopy, what are they looking for?

C-Reactive Protein (CRP)

When your healthcare team takes a blood test, they may be monitoring your C-reactive protein – or CRP – levels. CRP is released by the liver when inflammation is present in the body. It’s like a thermometer for inflammation – when CRP is low, inflammation is well-controlled; when CRP is high, inflammation is active (and therefore something may be wrong).

Because monitoring CRP is less invasive than a scope and less expensive than a scan, it’s commonly used to measure the severity of an IBD flare and/or the success of treatment. It can also be used to gauge whether or not inflammation is returning when therapy has been tapered or suspended.

One drawback to relying on CRP is that it’s not exclusively associated with inflammation of the GI tract. This means joint inflammation or an open sore, or even a tooth infection might contribute to a higher CRP level. Other challenges include its variability amongst individuals – some (about 20% of) people simply don’t make much CRP unless they are very, very sick; for these patients, a normal CRP is not very informative. In patients who know they increase their CRP during a flare, it can be very helpful. That’s why it’s important for patients to understand if they are CRP makers – both during a flare, and during periods of remission.


When your healthcare team requests a stool sample, they may be interested in evaluating its calprotectin content. Calprotectin is a major protein found in inflammatory cells in both blood and stool. During periods of GI inflammation, the stool will contain higher than normal levels of calprotectin. These levels will be even higher when there’s visible ulceration within the GI tract. That’s why stool samples are helpful in assessing one’s IBD status (high calprotectin = active disease; low calprotectin = stable disease).

One major advantage of stool samples (over blood tests) is that they are more localized. Whereas blood passes through virtually all parts of your body, your stool passes through your intestines only. This means your stool specifically reflects what’s going on in your GI tract – and this makes it an especially useful substance for monitoring IBD.

Endoscopy and scans

Sometimes, if you are experiencing signs and symptoms that suggest active inflammation or structural damage (blockages, abscesses and/or fistulas) your doctor will want more than a blood or stool sample. He/she will want to actually see the tissue in order to determine the nature of the problem – its location and severity. If this is the case, your doctor may arrange for an endoscopy or a CT scan.

In an endoscopy, your doctor inserts a thin, flexible tube – attached to a light and tiny camera – into your GI tract. This device captures images of the intestinal lining and allows the doctor to take samples (or biopsies) of the tissue for evaluation under a microscope. Endoscopies look at one part of your GI tract at a time, and may not view all of your GI tract.

Colonoscopy and sigmoidoscopy are two common types of endoscopy used for monitoring inflammation in IBD. Colonoscopy can be used to look at the whole colon and lower part of the small intestine whereas as sigmoidoscopy shows only the rectum and lower part of the colon. Upper endoscopy views the esophagus, stomach, and the first part of the small intestine (the duodenum). Some people will have inflammation in the small intestine between the duodenum and the colon. This region makes up about 18 feet of small intestine. If your doctor needs to see the lining of the small intestine, a balloon endoscopy or capsule endoscopy will be used. Your doctor will select the most appropriate option for you, based on your symptoms and disease history.

While endoscopy sees the inside of the intestines, a CT or MR scan takes images from several different angles to create a complete picture of your GI tract. This allows your doctor to see the intestines, as well as areas outside of the intestines, and then visually identify areas that look actively inflamed or strictured, and to see problems like fistulas or abscesses.

And while prepping your body for these sorts of procedures can be uncomfortable and unpleasant, they are invaluable screening methods that will allow your doctor to better understand your disease course, and thus provide you with the best possible care.

Monitor your doctor’s monitoring

It can be upsetting and overwhelming to think about the numerous ways in which Crohn’s disease can compromise your digestive system and threaten your health. But by understanding how the disease progresses and recognizing the signs and symptoms of its related ailments, you can stay on top of your condition and exercise more control over your life.

While it may be up to your doctor to select the best monitoring methods for your IBD, this doesn’t mean you should sit back and play a spectator role. Ask what types of biological indicators your doctor is screening for. It is important to know at any point in time whether you have active inflammation. Just like a diabetic needs to monitor the level of sugar in their blood, you should monitor the amount of inflammation in your intestines.

Patients who have been doing very well (in remission) may only need to measure their inflammation once a year. Patients who have had a flare in the past year, or have had complicated disease should be monitored more often, usually about every 3 months. Any time you start a new therapy, you should measure your level of inflammation before you start, and after the therapy should be working (8-16 weeks). An effective therapy should make the inflammation go away. Go over your test results with a member of your healthcare team and have them explain – at a basic level – what it all means. Inquire about self-monitoring practices and any available resources that might help you track your condition.

And remember – inflammation is the precursor for many Crohn’s-related complications. And although inflammation doesn’t always cause symptoms, it can silently wreak havoc on your intestines. Trust your gut (pardon the pun) and when you’re feeling sick or strange, consult a healthcare professional. It could be a good time to measure your level of inflammation.