IBS and Crohn's disease can both cause belly pain, diarrhea and urgent trips to the bathroom, but they are different kinds of illness. Crohn's is a chronic inflammatory disease of the digestive tract that can progressively damage the bowel.[1] IBS comes from disordered communication between the gut and the brain, with altered gut movement and oversensitive gut nerves, and it doesn't damage the bowel or raise the risk of cancer or death.[2][3][14] That's why the two are treated so differently, and why getting the right diagnosis matters. For inflammatory bowel disease (IBD) as a whole, see IBS vs IBD.
What is the difference between IBS and Crohn's disease?
| IBS | Crohn's disease | |
|---|---|---|
| What it is | A disorder of gut–brain interaction[3] | A chronic inflammatory disease driven by a dysregulated immune response in genetically susceptible people[1] |
| Inflammation | None visible, though subtle immune changes have been found in some people[2] | Patchy, in segments, and through the full thickness of the bowel wall (transmural)[1] |
| Where | No visible disease in the gut[14] | Most often the end of the small intestine (terminal ileum) and the start of the colon; it can also involve the upper digestive tract and the area around the anus[1][5] |
| Who gets it | More common in women and people under 50[6] | Typically young people; in one US population study, 56% were diagnosed between ages 17 and 40[4][5] |
| Core symptoms | Abdominal pain linked to bowel movements, with changes in stool frequency or form[7] | Abdominal pain, chronic diarrhea, weight loss and fatigue[4] |
| Diagnosis | Typical symptoms, no alarm features, and normal simple blood and stool tests[3] | Ileocolonoscopy with biopsies, plus blood tests and cross-sectional imaging[1] |
| Long-term course | Comes and goes; not linked to a higher risk of cancer or death[2][3] | Narrowing (strictures) or penetrating complications in about half of people within 20 years in one US study[5] |
| Treatment | Diet, soluble fiber, psychological therapies and medicines for the main symptom[3][6] | Advanced therapies that aim to heal the bowel lining, and sometimes surgery[1][4] |
IBS vs Crohn's symptoms: what's different?
Symptoms overlap a lot. The American College of Gastroenterology (ACG) notes that symptoms alone can't always tell IBS with diarrhea apart from IBD.[6] Some features, though, point one way or the other.
More in keeping with IBS:
- Pain that's clearly tied to bowel movements, easing or worsening when you go[7]
- Symptoms that come and go over months or years while you otherwise stay well[2]
- Normal blood and stool tests[3]
Point toward Crohn's or another condition:
- Weight loss you didn't intend, and fatigue[4][6]
- Blood in the stool, or black, tarry stools[6]
- Anemia, fever or symptoms that wake you at night[13]
- Abnormal blood results, including micronutrient deficiencies[1]
- Problems around the anus (perianal disease)[5]
- A family history of IBD[6]
It helps to keep the odds in mind: IBD is uncommon among people with IBS symptoms, especially when there are no alarm features. The ACG cites a pretest probability of under 0.5% to 1.2%.[6]
Do I have IBS or Crohn's? The tests that tell them apart
- Fecal calprotectin is a stool test for inflammation in the bowel. The ACG suggests it (or fecal lactoferrin), with a CRP blood test, for suspected IBS with diarrhea and no alarm features. UK guidelines advise it for people under 45 with diarrhea.[6][3] In a meta-analysis, a calprotectin of 40 µg/g or less, or a CRP of 0.5 mg/dL or less, meant a 1% or lower chance of IBD.[8]
- Ileocolonoscopy with biopsies, which examines the colon and the end of the small intestine, is the gold standard for diagnosing Crohn's.[1]
- Cross-sectional imaging, such as MRI or CT, shows how deep and how far the inflammation extends and whether there are complications.[1]
In IBS, these tests are normal. For the full IBS workup, see how IBS is diagnosed.
IBS vs Crohn's vs ulcerative colitis
Ulcerative colitis is the other main type of IBD. Unlike Crohn's, it is limited to the rectum and colon, to a variable extent. People usually first notice bloody diarrhea, and it's diagnosed from clinical, laboratory, endoscopic and biopsy findings together. Treatment aims to control inflammation and keep it in remission, and 10–20% of people still need surgery to remove the colon and rectum.[9] In short: Crohn's can be patchy and reach through the whole bowel wall, ulcerative colitis stays in the colon and rectum, and IBS causes no visible inflammation at all.[1][9]
IBS vs colitis: what about other kinds?
"Colitis" means inflammation of the colon, so ulcerative colitis and Crohn's affecting the colon are both forms of it. One type is easy to mistake for IBS: microscopic colitis. It causes chronic watery, non-bloody diarrhea, often with urgency and nighttime stools, while the colon looks normal or almost normal at colonoscopy. Only biopsies show it.[10] It's more common in women and smokers, and it's linked with regular use of proton pump inhibitors, NSAIDs and SSRI antidepressants.[10] In a meta-analysis, a third of people with microscopic colitis had symptoms that met criteria for IBS.[11] Fecal calprotectin can't rule it out, so European guidelines advise checking for it in people with IBS-type diarrhea who have these risk factors or don't respond to IBS treatment.[10]
Can you have IBS and Crohn's at the same time?
Yes. In a 2020 meta-analysis of 27 studies, 32.5% of people with IBD in remission had symptoms that met criteria for IBS. The figure was 36.6% in Crohn's disease, and about a quarter of people still had them when remission was confirmed by colonoscopy or biopsy.[12] So if you have Crohn's and still have symptoms, ask your IBD team to check for active inflammation, because active Crohn's and IBS-type symptoms are treated differently.
When should you see a doctor?
See a doctor if you have ongoing bowel symptoms without a diagnosis, or promptly if you notice any of these: blood in your stool, black stools, weight loss you didn't intend, anemia, fever, symptoms that wake you at night, pain or swelling around the anus, or a family history of IBD or bowel cancer.[6][13][5] Get urgent care for severe pain, heavy bleeding or a high fever. Before the appointment, note your stool type and frequency, any blood, night-time symptoms and weight changes; a Bristol stool chart makes this easier. For the full list of warning signs, see IBS red flags.