Why Irritable Bowel Syndrome Is Difficult to Diagnose


Jennifer Larson

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Woman with stomach pain

Your belly is sore and swollen, maybe extra gassy, and you’ve been experiencing regular bouts of diarrhea or constipation on a regular basis for several months. It must be irritable bowel syndrome, right?

Maybe. But maybe not. Abdominal pain and changes in bowel habits are two major hallmarks of irritable bowel syndrome, or IBS. As many as 10-15% of people around the world are affected by IBS, making this disorder of the large intestine a fairly common occurrence. Two out of three IBS sufferers are female.

But you can experience those same symptoms with other conditions. IBS is considered a functional gastrointestinal disorder (abnormal bowel function without identifiable anatomic cause), so it can be very difficult to diagnose. An IBS diagnosis may not be the right diagnosis for some people experiencing those symptoms. In fact, if they also are experiencing certain other symptoms, it could be time to seek additional testing.

The Different Types of IBS

An IBS diagnosis typically falls into one of four categories:

  • IBS-D, in which diarrhea is predominant

  • IBS-C, in which constipation is predominant

  • IBS-M, in which the person experiences a mix of diarrhea and constipation

  • IBS-U, which is the “unclassified” category because the symptoms can’t be grouped under any of the other categories

But even choosing a diagnosis of one of those four subtypes doesn’t mean the diagnosis is set in stone. You might be diagnosed with IBS-C, only to realize a few months later that your symptoms are much more consistent with IBS-D. And in fact, about 29% of people with IBS do switch back and forth between IBS-C and IBS-D.

So even if the IBS diagnosis is correct at the type of diagnosis, it may change over time. And it may change many times.

Other Possible Diagnoses

It could be IBS. But a person experiencing common IBS symptoms like abdominal pain, bloating and other gastrointestinal discomfort could actually have developed another condition or disease. The possibilities include:

  • Inflammatory Bowel Disease (IBD)

  • Bowel cancer

  • Ovarian cancer

  • Stomach cancer

  • Endometriosis

  • Celiac disease

  • Carcinoid syndrome

However, current guidelines don’t require extensive diagnostic imaging or lab testing for IBS unless a person is under 50 and has experts call “alarm features.” Those features, which are symptoms or characteristics that raise the alarm that something else may be occurring and require additional testing, include:

  • Iron-deficiency anemia

  • Unintentional weight loss

  • Family history of GI disorders such as IBD or colorectal cancer

  • Blood in your stools

  • Fever

Those alarm signs should send you to your doctor to ask for consideration of other disorders. Also, if you experience a change in the type or severity of your symptoms, or you’re over 50 and begin to develop symptoms, you should also ask for testing for other disorders or conditions. Your doctor may choose to perform some other tests to rule out IBS. Those tests could include a complete blood count, a metabolic panel, a stool study, thyroid function tests, and tests for celiac disease.

You may not actually have another condition, but it’s worth getting more information to make sure. At worst, you’ll have more information that may help you manage your condition.

Get Checked Out

Certain factors, such as stress, can make IBS symptoms worse for a prolonged period of time, but they won’t cause the symptoms to begin with. So any noticeable or persistent change in bowel habits is a good reason to seek medical help. Depending on your symptoms and your family history, your doctor may want to consider additional testing.

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Medical Reviewers: William C. Lloyd III, MD, FACS Last Review Date: Aug 14, 2017

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Medical References

  1. Diagnosis of IBS. International Foundation for Functional Gastrointestinal Disorders, Inc. https://aboutibs.org/diagnosis-of-ibs.html
  2. Irritable bowel syndrome: Tests and diagnosis. Mayo Clinic. http://www.mayoclinic.org/diseases-conditions/irritable-bowel-syndrome/basics/tests-diagnosis/con-20...
  3. Leher JK. Irritable Bowel Syndrome. Medscape. April 4, 2017. http://emedicine.medscape.com/article/180389-overview