Irritable Bowel Syndrome (IBS) vs Inflammatory Bowel Disease (IBD)

There are many different types of bowel conditions but IBS and IBD are among the two most common. These are two conditions are often confused with each other. Despite the commonality in location and some symptoms between both conditions, irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are two entirely separate conditions. One is a disease, the other is not. One is associated with a higher risk of cancer, the other other is not. One may require surgery to remove a portion of the bowel, the other does not. But both conditions can be debilitating and adversely affect a person’s quality of life.

Disease or Disorder

Ulcerative Colitis Picture 1

Inflammatory bowel disease is a disease as the name suggests but irritable bowel syndrome is a functional disorder. This means that in IBS there is no pathological (disease-related) changes in the bowels but yet the condition occurs. Functional disorders are believed to be an abnormality in normal body functions. With irritable bowel syndrome, it appears that the movement through the bowels are either too fast or too slow. In inflammatory bowel disease however, the problem is that the bowel is inflamed for some reason. It is believed to be autoimmune in nature. This culminates in lesions like ulcers forming within the bowel walls.

Types of IBS and IBD

There are two types of IBD – ulcerative colitis and Crohn’s disease. However, there is an additional non-specific form of IBD that is similar to ulcerative colitis. Ulcerative colitis tends to be limited to the inner two layers of the bowel and causes shallow ulcers. Crohn’s disease extends through the entire wall of the bowel and causes deeper lesions. Irritable bowel syndrome can be classified according to the alteration in bowel habit. On this basis, there may be three types:

  • Diarrhea-predominant IBS where a person experiences frequent bowel movements and recurrent episodes of diarrhea.
  • Constipation-predominant IBS where there is difficulty to pass stools and infrequent bowel movements.
  • IBS with alternating constipation and diarrhea where a person may experience episodes of constipation and diarrhea.

Part of the Bowel Affected

stomach colon rectum

The part of the bowel involved in irritable bowel syndrome cannot be conclusively identified. It seems to extend through most of the lower gastrointestinal tract, from the small intestine all the way to the colon. But it may include the entire gut. The part of the bowel affected in IBD can be more definitively identified with diagnostic investigations like an endoscopy or colonoscopy. In ulcerative colitis, the inflammation is limited to the colon. But with Crohn’s disease the inflammation can occur anywhere in the gut, from the mouth all the way to the rectum. However, it is mainly a portion of the small intestine known as the ileum that is affected in Crohn’s disease.

Symptoms of IBS vs IBD

There are many similar symptoms of IBS and IBD, such as:

  • Alterations in bowel habit – mainly diarrhea in IBD.
  • Abdominal pain, often relieved by defecation in both IBD and IBS.
  • Changes in appetite.
  • Weight loss, more pronounced in IBD than IBS.

Symptoms like bloody stool or mucus in the stool are seen in inflammatory bowel disease (IBD) but not irritable bowel syndrome (IBS). Sometimes there are symptoms outside of the gastrointestinal tract in IBD, like erythema nodosum (skin lesions). These extra-intestinal symptoms do not occur in IBS.

Causes and Triggers

The exact cause of both IBS and IBD remains unknown. It seems unlikely that both conditions are caused by the same factors despite a family history being the common risk in both conditions. Similarly certain foods may serve as triggers but it is highly variable in both conditions and from sufferer to the next. IBD is thought to be an immune-related condition, possibly associated with a viral infection or autoimmune in nature. IBS is largely associated with abnormalities in the nervous system which is believed to affect the muscles in the wall of the bowels. This in turn results in overactivity or underactivity of the bowels.

Risk of Bowel Cancer

Irritable bowel syndrome has no associated risk with bowel cancer. When bowel cancer does occur in IBS patients, it is either unrelated or the IBS may have been incorrectly diagnosed. Inflammatory bowel disease (IBD) has a strong associated risk with colorectal cancer, irrespective of whether it is ulcerative colitis or Crohn’s disease. However, the cancer risk is much greater with ulcerative colitis than with Crohn’s disease. Patients with Crohn’s disease affecting the small intestine are at a greater risk of small bowel adenocarcinoma. Regular screening is therefore advisable in IBD patients.

Diagnostic Tests and Scans

colonoscopy

The diagnostic investigations conducted for inflammatory bowel disease and irritable bowel syndrome are largely the same. This includes a colonoscopy, flexible sigmoidoscopy, barium enema, CT scan, MRI, stool and blood tests. Positive findings on one or more of these tests may confirm inflammatory bowel disease. But with irritable bowel syndrome the results/findings should be negative. Irritable bowel syndrome is only diagnosed when all other bowel disorders have been excluded as possible causes of bowel-related symptoms. A test to measure the bowel transit time, meaning the time that food takes to move from the mouth to the anus, may be faster or slower than normal even in IBS.

Medication for IBS vs IBD

IBS is incurable. But the medication used to manage the condition can help to relive symptoms like pain, constipation and diarrhea. Other drugs work by acting on the nerves of the bowels. Many IBS patients do not use chronic medication but in severe cases it may be necessary.  It can reduce painful cramps and slow down bowel motility. With IBS, the drug approach is significantly different. Some drugs may be used to control the symptoms like in IBS. But the main aim of drug therapy is to reduce inflammation. This is done with anti-inflammatory drugs and immune suppressants. Antibiotics are also used in IBD, and sometimes for IBS.

Surgery for IBS vs IBD

Thus far, surgery has not been shown to be helpful in the management of irritable bowel syndrome (IBS) in any way. However, it is conducted for severe cases of inflammatory bowel disease (IBD) that is not responding to drugs. It can eliminate ulcerative colitis completely but would require that the entire colon and rectum be removed. Surgery may allow Crohn’s disease to shift into remission for long periods of time when he diseased portion of the gut is removed. Usually surgery is not the first treatment option for inflammatory bowel disease (IBD) unless there is evidence of cancerous lesions in the bowel.

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  • Lynn

    I’ve been having issues for the past 6 months or so with gas/bloating. More often times than not the gas is “erupting” inside my stomach, rather than coming out as flatulence. I have bouts of constipation and diarrhea. My stools start out in the morning loose-normal and then as the day goes on (I can go maybe 3-4 times a day), it gets more difficult and the stool becomes more clay-like. Most of my gas/bloating/cramp symptoms occur later in the day. I’ve had an ultrasound, celiacs test, and a lactose intolerance test, all negative without significant findings. My diet has not changed much, except I am eating LESS junk (cakes, cookies, etc). I find it odd this came out of nowhere. I have never had stomach issues in the past. I am curious if any of this could be IBD or IBS related…

  • Hi Lynn. It would be leaning more towards IBS. Remember that IBS is a functional bowel disorder that is usually diagnosed when all other conditions have been eliminated through some of the tests you mention in addition to other investigations like a colonoscopy. There are specific diagnostic criteria that would also be applied but from what you are reporting it seems that your condition will fit into most of these IBS criteria. With IBD your doctor may see some degree of inflammation and/or ulceration in the bowels with a colonoscopy. You should be seeing a gastroenterologist and undergo a colonoscopy if you have not as yet had one. Once there is no identifiable bowel disease, a diagnosis of IBS will be considered.

  • DARLENE REID

    my symptoms are painful when having a bowel movement my stool are loose
    the pain feel like labor pain my heart beats fast I feel like iam going to past out

  • Hi Darlene. It would be advisable to have a colonoscopy to verify that there are no lesions or inflammation in the bowel. It is difficult to say whether it is IBS or IBD solely by these symptoms. Some people do have what’s known as a vasovagal reaction usually caused by the pain – this causes symptoms like sweating, rapid heart rate, palpitations and dizziness. Your doctor will be able to advise you further.

  • disqus_Y2Jph8NSNl

    Hi, I have been suffering with severe nausea and stomach pains and have been feeling generally “unwell” for the past 2 and a half years. I have undergone many tests, with a capsule endoscopy showing small patches of inflammation. Surely this means it is not IBS as there is a problem with the histology?

  • disqus_Y2Jph8NSNl

    I have been suffering with severe nausea and stomach pains and have been feeling generally “unwell” for the past 2 and a half years. I have undergone many tests, with a capsule endoscopy showing small patches of inflammation. Surely this means it is not IBS as there is a problem with the histology?

  • Hi. It is somewhat of a yes and no answer to your question. Previous thinking was that inflammation would immediately indicate a pathology and therefore IBS would not be considered as a diagnosis. As you obviously know, IBS is only diagnosed when the “typical” IBS symptoms are present and no pathology (like inflammation) in the bowels can be isolated. However, there is a current theory that microscopic inflammation does occur in IBS. Here’s a link to the article from a Canadian university (http://reference.medscape.com/medline/abstract/15862932). It is thought to be a type of post-infectious IBS. It may be worth discussing this with your gastroenterologist if you are still uncertain. Hopefully other inflammatory bowel conditions have been conclusively ruled out.

  • bernadette bell

    I’ve been diagnosed with ibs with only blood tests and a colonoscopy. I bleed alot when it occurs, how is it only ibs? I’m getting a new dr soon.
    -hopelesslywautingforinsurance

  • Sagar

    Hi everyone.i m 30 years old guy.last November I suffered with a bad diarrhea around 4-5 episodes a day which contain pus oftenly.stool test was done which shows both pus cels and rbc plenty and occult blood was positive and was treated with cefixime.my diarrhea resolved but I started suffering with bloating and excessive flatus and lower abd pain.so stool test was repeated which shows normal except positive occult blood.then colonoscopy and endoscopy was performed which appears normal.so I was advised for capsule endoscopy which shows some small patch type lesion but not ulcer in terminal ileum.so again colonoscopy was done reached to terminal ileum and biopsy was taken which histopathological examination shows lymphoid hyperplasia.other findings were normal.so this January again I went for colonoscopy which shows normal terminal ileum without any lesion.but nowdays I keep on having one or two episodes of watery stool in every 15- 20 days since 2 months.please note that before these two months I was doing fine.my dr say nothing to worry but I often have lower abd pain too.so please any suggestion will be highly appreciated .thank you.

  • Sagar

    Hi everyone.i m 30 years old guy.last November I suffered with a bad diarrhea around 4-5 episodes a day which contain pus oftenly.stool test was done which shows both pus cels and rbc plenty and occult blood was positive and was treated with cefixime.my diarrhea resolved but I started suffering with bloating and excessive flatus and lower abd pain.so stool test was repeated which shows normal except positive occult blood.then colonoscopy and endoscopy was performed which appears normal.so I was advised for capsule endoscopy which shows some small patch type lesion but not ulcer in terminal ileum.so again colonoscopy was done reached to terminal ileum and biopsy was taken which histopathological examination shows lymphoid hyperplasia.other findings were normal.so this January again I went for colonoscopy which shows normal terminal ileum without any lesion.but nowdays I keep on having one or two episodes of watery stool in every 15- 20 days since 2 months.please note that before these two months I was doing fine.my dr say nothing to worry but I often have lower abd pain too.so please any suggestion will be highly appreciated .thank you.

  • HI Sagar. It is more than 6 months since your last endoscopy and since your symptoms are persisting it may be worth investigating again. You should see a gastroenterologist if you have not done so already. However, the symptoms are not very serious – one or two episodes every few weeks is not debilitating. The more common bowel conditions like inflammatory bowel disease need to be excluded.

  • Sagar

    Dear sir do u think my symptoms can be due to chronic hepatitis .plz do reply.thank you