As for what causes IBD, both ulcerative colitis and Crohn’s disease happen when a person’s immune system accidentally attacks their GI tract, according to the NIDDK. Ulcerative colitis and Crohn’s disease are separate conditions, but they do share a few risk factors. Both diseases tend to run in families, so researchers are working to understand the connection, according to the Mayo Clinic. Both also usually start causing symptoms before a person turns 30 and are more likely to affect those of Eastern European Jewish descent.
There’s also a question of how a person’s environment or lifestyle factors, like medications and diet, may cause or exacerbate both IBD and IBS.
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How do you get an IBS diagnosis or an IBD diagnosis?
There’s no definitive test for IBS, so doctors typically diagnose it after excluding most other potential causes. In addition to evaluating your symptoms, they may perform a host of exams to identify the problem.
For example, they may order a colonoscopy or a flexible sigmoidoscopy (using a thin tube to examine your rectum and only part of your colon) to see if your gut shows signs of inflammation. IBS symptoms can also mimic an overgrowth of bacteria in your gut or parasites, so your provider might want to conduct a stool sample to check your poop for germs, according to the Mayo Clinic.
Because celiac disease, an immune response to eating gluten, can cause similar symptoms, doctors may want to take a blood test to rule it out before diagnosing you with IBS, says Jill Deutsch, MDa gastroenterologist at Yale Medical and an assistant professor at Yale School of Medicine. Once celiac and any other conditions your doctor wants to explore are ruled out, IBS can usually be diagnosed based on your symptoms.
Diagnosing IBD can be similarly time-consuming. Your doctor will likely order a range of tests to pick up on any abnormalities that could signal these conditions, including blood tests, a colonoscopy, a flexible sigmoidoscopy, or an x-ray or CT scan. They may also test your poop to see if any blood is present. According to Dr. Hanauer, doctors often look for white blood cells—which may signal inflammation in the gut—in your stool if they’re testing for inflammatory bowel disease.
If your doctor suspects Crohn’s disease has affected your small intestine, they may also have you do exams like a capsule endoscopy, which involves swallowing a capsule that has a camera in it to view your intestines. An external recorder captures the images, and you’ll later poop the capsule out.
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What does IBS treatment look like vs. IBD treatment?
Although IBS and IBD share commonalities, they aren’t managed in the same way. “The treatment of IBD is focused on controlling inflammation. IBS treatment is about controlling the heightened sensitivity to what’s going on in the gut,” Dr. Hanauer says.
If you’re diagnosed with IBS, your doctor may recommend a range of treatment options depending on your exact symptoms, and it can take some trial and error to get it right. According to the Mayo Clinic, if you have IBS-C (which causes constipation), your doctor might suggest adding more fiber to your diet since it soaks up water as it moves through your digestive system, making your poop softer and easier to expel. They may also recommend laxatives or prescription medications that boost the amount of fluid that gets into your poop.