IBD vs. IBS: What’s the Difference?

It’s easy to confuse IBD (inflammatory bowel disease) and IBS (irritable bowel syndrome). Looking at their acronyms, it’s easy to mix up which one is which, or even to assume that they are different variations of the same disease.  

This is far from the truth. These are two separate conditions with very major differences in pathology, symptoms, and treatment. 

The biggest difference between the two? IBD causes visible damage to the digestive tract due to chronic inflammation, whereas a colonoscopy of a patient with IBS would show *no* inflammatory damage. In fact, despite their symptoms, their digestive tract would look perfectly fine.

What is inflammatory bowel disease?

“Inflammatory bowel disease is generally thought of as Crohn's disease and ulcerative colitis,” says Benjamin Cohen, MD, gastroenterologist at The Mount Sinai Hospital in New York City.

Both Crohn’s disease and ulcerative colitis occur when the immune system — which is supposed to attack foreign pathogens to protect the body from illness — attacks the digestive tract instead. The continuous attacks lead to chronic inflammation and damage, and cause symptoms like diarrhea, abdominal pain, and rectal bleeding.

“Crohn's disease can occur anywhere from the mouth to the anus,” says Dr. Cohen. “It can occur in skip fashion, so you can have one area of bowel that's affected, then another normal area, and then another area that's affected.” That said, Crohn’s disease most commonly affects the small intestine, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

Ulcerative colitis, on the other hand, “is continuous inflammation beginning in the rectum and extending upwards, and only occurring in the colon,” says Dr. Cohen.

What is irritable bowel syndrome?

The word syndrome generally refers to a cluster of related symptoms with an unknown cause. While syndromes cause real symptoms that can affect quality of life, they may not cause visible damage that appears on imaging tests or lab work.

There is some overlap between symptoms of IBS and IBD: Both are known to cause abdominal pain and diarrhea, for example. However, IBS is generally not associated with bloody stool (unlike IBD), and IBS pain tends to be relieved (or at least lessened) after a bowel movement. Here are more signs your stomach pain is actually IBS. 

IBS can affect patients in a few different ways: Doctors may diagnose a patient as diarrhea-predominant (IBS-D), constipation-predominant (IBS-C), or have alternating episodes of diarrhea or constipation (IBS-M, as in “mixed”). These episodes can be triggered by certain foods, such as dairy products or caffeinated beverages, or they can occur during periods of high stress. 

Although both IBS and IBD can have a significant impact on quality of life without treatment or lifestyle changes, IBD often requires more aggressive treatment in order to minimize the risk of complications and damage to the digestive tract — so it’s important to get an accurate diagnosis and seek treatment.