The Differences Between IBD and IBS

Two disorders that are frequently confused, although they are completely different conditions, are irritable bowel syndrome (IBS) and inflammatory bowel disease (which includes both Crohn's disease and ulcerative colitis, collectively known as IBD). Although IBS and IBD sound similar because of their acronyms and might cause similar symptoms, they are totally distinct conditions with very different disease courses. In addition, they are treated quite differently and the medications used for one are not going to be helpful for the other.

Close up of the sliding weights on a medical scale
Ian Hooton / Getty Images

IBS is a functional disorder: even though the symptoms are real and can be severe, there are no abnormalities found in the small or large intestine during testing, such as an endoscopy, and no evidence of disease is found during the examination of a biopsy of intestinal tissue. IBD, however, is a disease that causes obvious abnormalities that are seen during testing. When IBD goes untreated it can lead to serious complications that can occur both inside and outside of the digestive system, while IBS is not associated with these issues. In addition, complications from IBD can be severe enough to be life-threatening, while this is not true for IBS.

In view of all these factors, the differences between IBD and IBS are actually quite significant, although it might not seem that way on the surface because they both routinely cause diarrhea and pain. Many people commonly confuse the two conditions or even use incorrect terms like "irritated bowel disease" or "inflammatory bowel disease," both of which are not correct terms and are not conditions that exist.

IBS and Ulcerative Colitis Are Different

IBS is often confused with ulcerative colitis or colitis, but they are not the same condition. Both conditions affect the large intestine and may cause diarrhea, but that is as far as the similarities go.

IBS is a syndrome, it is not a disease. Ulcerative colitis is associated with a risk of colon cancer, and having IBS does not increase the risk of colon cancer. IBS does not cause intestinal bleeding and ulcerative colitis does.

"Colitis" is a rather broad term that refers to any general inflammation in the colon and it could be caused by several different conditions, including bacterial infections or IBD. Colitis is a sign of ulcerative colitis or of Crohn's disease—it is not a part of IBS.

Differences in Treatments

Therapy and medications for IBS vary hugely from those for IBD. An incorrect diagnosis and treatment plan can not only be ineffective but, in some cases, can also be dangerous.

Treatments for IBD often involve drugs, such as immunosuppressives, biologics, and steroids. IBS is often treated with diet and lifestyle changes, but when drugs are needed, antispasmodics or antidepressants are sometimes used.

Endoscopic Differences

Endoscopy refers to the tests that are done to look inside the intestines or other body structures. In some cases, people who are suspected of having IBS may have a colonoscopy or other tests to rule out other potential conditions.

When a physician looks inside the colon of a person with IBS, there will be no evidence of disease found. This is because IBS is a functional disorder, not an organic disease, and it does not cause changes in the intestinal wall.

Crohn's disease and ulcerative colitis can cause extensive damage to the intestinal walls. When looking inside the colon of a person with Crohn's disease in the large intestine, a physician may see ulcers (or holes), inflammation, and parts may look like cobblestone.

Biopsies (pieces of tissue taken from the body and sent for evaluation under a microscope) will show even more changes. The colon of a person with ulcerative colitis will also show inflammation and ulcers, and a biopsy will show changes in the cells.

The table below is by no means a complete or hard-and-fast list of signs and symptoms but does give a general idea of the basic distinguishing factors between IBS and IBD.

Differences Between IBD and IBS

Intestinal Symptoms IBS Crohn's
Alternating diarrhea/constipation X
Abdominal pain X X X
Bloating/Distension X X X
Mucus X X X
Persistent diarrhea X X X
Loss of Appetite X X
Rectal bleeding X X
Fistulas X
Strictures X
Extra Intestinal Symptoms IBS Crohn's
Worsening of symptoms during menses X X X
Anemia X X
Delayed growth and sexual maturation in children X X
Eye irritations X X
Fever X X
Skin irritations X X
Weight loss X X
Related Conditions IBS Crohn's
Urinary Conditions X X X
Fibromyalgia X X X
Anxiety X X X
Depression X X X
Arthritis X X
Liver Complications X X
Osteoporosis X X
Colon Cancer X X
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By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.