What is the diagnosis process of Irritable Bowel Syndrome?

If you are suffering from digestive distress, every day can seem like a difficult journey in avoiding symptoms.  Without a diagnosis, proper treatment can be difficult, and symptoms may persist.  If you have been tested for celiac disease and inflammatory bowel disease, and have been cleared, but digestive symptoms persist, then you may have irritable bowel syndrome (IBS).  Although the process may be lengthy and cumbersome, a diagnosis of IBS is worth the wait since treatment options will be clearer, so you can start feeling better.

What is irritable bowel syndrome?

Irritable bowel syndrome is a common disorder of the large intestine that affects nearly 10 to 15-percent of the population globally. Common symptoms of IBS include:

  • Abdominal pain
  • Constipation, diarrhea, or both
  • Gas
  • Bloating
  • Mucus in the stool

There is no known cause of irritable bowel syndrome, but some contributing factors may include:

  • Motility issues in the intestinal tract. If contractions in the intestine are over-stimulated, they can lead to gas, bloating, and diarrhea. However, if contractions are weaker, than it can slow the movement of food through the digestive tract and lead to constipation and hard stools.
  • Inflammation in the intestinal tract. Some people with IBS may have an increased number of immune system cells in the intestinal tract that can lead to symptoms such as abdominal pain and diarrhea.
  • Gut health issues. An imbalance in the “good” and “bad” bacteria in the gut may have an impact on the digestive issues linked with IBS.

How do I get diagnosed with IBS?

IBS diagnosis can be a lengthy process, since it will be a lot of process of elimination of other digestive disorders. Typical testing done in the process of IBS diagnosis includes:

  • Food tolerance testing can be done to help determine which foods you may be sensitive to or allergic to. Although food allergies are not often related to IBS, those with IBS are usually intolerant to foods like milk products and gluten.  Patch testing for food allergies can be ordered under the care of a qualified healthcare professional and they can help interpret results for you. Antibody allergy testing has mixed reviews, but an elimination diet supervised by a dietitian may also be helpful in figuring out what foods are causing symptoms, if any. Breath testing can also be used to see if you may be lactose intolerant, which is common in those with IBS.
  • Celiac disease testing will start with a blood test called tTG-IgA. If this test reveals antibodies for celiac disease, then the next step will be an outpatient biopsy of the small intestine to see if damage consistent with celiac disease is present. This procedure is an endoscopic procedure that will also be able to look for any inflammation in the intestinal tract. An endoscopy basically involves short-acting anesthesia so that a tubing with a small camera can travel through the intestinal tract to look for any inflammation or abnormalities.
  • Colonoscopy testing is not usually done until after the age of 50 in most people. However, if you are younger than this and are presenting symptoms of intestinal distress such as chronic constipation, painful abdominal cramping, etc., then your gastroenterologist may recommend an earlier test. This test is similar to the endoscopic procedure but will be focused on looking at the large intestine for any inflammation or abnormalities. If polyps are found, then they can be removed during this procedure. This test can be used to look for any signs of inflammatory bowel disease (Crohn’s or colitis).
  • Intestinal motility tests will be used to see if the colon is evacuating waste efficiently. An example of this test is a SITZMARKS® test. The patient will swallow a capsule with markers in it on day one. The patient will then return to get x-rays done every few days during the week after swallowing the capsule.  The x-rays will be able to determine how many markers remain in the intestinal tract. The more markers still present after testing will reveal a weaker motility of the intestines in digesting and excreting waste.
  • Rectal exams and testing will help determine the strength of the rectal muscles and is used as a marker for diagnosing IBS.

Once testing is done, the physician will be able to determine the cause of your symptoms and then treatment options can be offered.

Take home message

Diagnosis for IBS can be a lengthy and time-consuming process. It can also be costly, especially if your insurance does not cover testing. Be sure to check with your health insurance company to see if certain testing will be covered. If you do not have health insurance, ask your healthcare provider what testing can be done economically to help determine the cause of your symptoms.

A good place to start treating symptoms in the meantime is the low FODMAP diet plan. Start eliminating common trigger foods of those with IBS and see if that helps reduce your symptoms. A registered dietitian can be a great resource in supervising you during this process to help you pinpoint trigger foods. Visit Casa de Sante for tips and resources for treating IBS.


Written by Staci Gulbin, MS, RD a Board-certified dietitian.

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