Both can cause stomach pain, bloating, and diarrhea or constipation. But that’s where the similarities end. IBS and IBD have different causes and treatments. You can’t tell which it is by how you feel, and you need to know the difference so you can get the right type of help.
Structural or Functional?
IBD is a structural disease. That means there is underlying physical damage that causes your symptoms. Doctors can see chronic inflammation or ulcers when they examine the gut with an X-ray, endoscopy, surgery, or biopsy. Crohn’s disease and ulcerative colitis are inflammatory bowel diseases.
IBS, on the other hand, is what doctors call a functional disease. Someone with this type of disease will have a group of symptoms, but tests won’t show any physical explanation for those problems.
Only Some Symptoms Shared
Since IBD and IBS are both chronic conditions that affect the gut, they have some overlapping warning signs: belly pain and diarrhea. Plus, they both tend to be diagnosed in young people.
But other symptoms are unique to IBD, caused by the inflammation in your gut. They include:
- Blood in your stools or black stools
- Weight loss or loss of appetite
- Progressively worsening symptoms
- Inflammation in the skin, joints, or eyes
If you notice these red flags, your doctor will likely suspect that you have IBD or another structural disease -- not IBS.
Doctors use something called the “Rome criteria” to decide if you have irritable bowel syndrome.
According to the criteria, you may be diagnosed with IBS if you have belly pain for at least 1 day a week for the previous 3 months. The pain must also meet at least two of the following:
- It is associated with a bowel movement.
- When it starts, you begin to have bowel movements more or less often.
- Your stools look different when it begins.
In some cases, doctors will diagnose you with IBS just using these standards. But in many cases, especially if you also have other symptoms that hint at IBD, you’ll get tests to find out whether there’s any bleeding or inflammation in your digestive tract. If there is, then you don’t have IBS.
Since it's a structural disease, a doctor needs to find physical damage in your gut to make the diagnosis. To look for inflammation, ulcers, and bleeding, you may get:
- Tests of your blood and stools
- A colonoscopy or other imaging tests to look inside your gut, with a biopsy
- CT scans
If you have inflammation and ulcers, your doctor can use these tests to narrow down what form of IBD you have. Crohn’s disease and ulcerative colitis are the two main types.
What Causes IBS and IBD?
Doctors understand better what causes the two conditions, since they have physical signs to help them.
The long-lasting inflammation in the digestive tracts of people with IBD can cause bleeding and ulcers (sores). In turn, this irritation causes pain and, by aggravating the immune system, leads to symptoms like fever and fatigue.
The causes of IBS aren’t as clear.
Scientists have found links between irritable bowel syndrome and the immune system, and how muscles move food through the gut. Many people have certain triggers that cause their symptoms to get worse, including some foods, stress, infections, and hormonal changes.
Treating IBS and IBD
People with IBS often try to treat it by changing what they eat. There is no specific diet that works for everyone who has the condition.
But you could ask your doctor if it would help to:
- Get more fiber (from food or supplements).
- Stop lactose, which is in dairy products.
- Cut down on foods that make you gassy or bloated.
- Get more water. (You can drink it or eat H2O-rich foods.)
- Avoid caffeine and legumes (beans).
- Limit or avoid “FODMAPs” (a certain type of sugar found in some fruit, vegetable, bread and dairy products).
Your doctor may also prescribe drugs to help with diarrhea or constipation if you need more relief. Other things that can help include stress management, acupuncture, hypnotherapy, and relaxation training. Researchers are also studying whether probiotics help tame IBS.
Counseling is also helpful, especially if the stress of having the condition starts to get to you, or if you notice you're limiting your social life because you worry about when your symptoms will affect you. A support group is another great resource, because the people there will understand, from personal experience, what it’s like to have IBS.
IBD, on the other hand, is more often treated with drugs that target the inflammation that causes symptoms. These powerful meds generally don’t work as a treatment for IBS, which is one reason why it’s so important to know which condition you have. And while some people with IBD need surgery to repair the physical damage to their digestive tract, surgery isn’t needed for IBS.
Lastly, an inflammatory bowel disease makes you more likely to get colorectal cancer. Irritable bowel syndrome doesn’t do that, but you should still keep up with your regularly scheduled screening tests.