What is Irritable Bowel Syndrome?

Mark Pimentel, MD: Hello, and thank you for joining this MD Magazine® Peer Exchange titled “Expert Perspectives on Diagnosis and Treatment of Irritable Bowel Syndrome.”

Irritable bowel syndrome [IBS] is a functional, gastrointestinal disorder affecting an estimated 1 of 6 people in the United States. Symptoms are variable and can range from mild to severe. But IBS is a long-term condition, so symptoms may come and go and change over time.

In this Peer Exchange panel discussion, I’m joined by my colleagues, who are experts in irritable bowel syndrome. We will review the causes, diagnostic work-up, management, and even emerging therapies.

I’m Dr Mark Pimentel, the executive director of the Medically Associated Science and Technology Program at Cedars-Sinai in Los Angeles, California.

Participating today on our distinguished panel are: Dr Bill Chey, a professor of medicine and a gastroenterologist at the University of Michigan in Ann Arbor, Michigan. Also joining me is Dr Tony Lembo, a professor of medicine at Harvard Medical School and the director of the GI [gastrointestinal] Motility Laboratory at Beth Israel Deaconess Medical Center, Division of Gastroenterology, in Boston, Massachusetts. On my right is Dr Ali Rezaie, the medical director of the GI Motility Program and the director of bioinformatics at the MAST [Medically Associated Science and Technology] Program at Cedars-Sinai in Los Angeles. And finally, Dr Brennan Spiegel, a professor of medicine and the director of health services research at Cedars-Sinai Health System in Los Angeles, California.

Thanks so much for joining us. Let’s begin.

The first part we’re going to talk about is understanding irritable bowel syndrome. What is IBS? And I know that seems like a very simple question, but it’s really not. Tony, can you take a crack at what IBS is? How do you sort of define it?

Anthony J. Lembo, MD: Sure. In the clinic, most patients who present with IBS have pretty typical symptoms. In fact, they always have abdominal pain as 1 of the distinguishing characteristics of IBS. It typically is a crampy pain, most often in the left lower quadrant, but it can involve any part of the belly. It has to be associated with some change in bowel habits. So it gets worse or better with a bowel movement or immediately after a bowel movement, or with a change of stool consistency—in the form of the stool. There are other symptoms that are commonly associated with IBS. Patients frequently present with abdominal bloating and urgency, and the stools can either be hard or loose, and sometimes they can vary in the same bowel movement. Patients can alternate between diarrhea and constipation.

There are several subtypes of IBS, and they’re based on stool characteristics. We have IBS with constipation, and those patients typically have hard stools that can be difficult to pass. Or we have IBS with diarrhea, where stools are loose and frequent and can be associated with urgency. Or we have IBS mixed, where they go back and forth between diarrhea and constipation. Sometimes patients will fall in the middle, but the majority of people are IBS-C [with constipation], IBS-D [with diarrhea], or IBS-M [mixed], and we’ll talk more about this as this program goes on.

Mark Pimentel, MD: But some of the definitions have changed over time, Brennan. It’s a little confusing for some people because of the Rome criteria change. What’s evolving in IBS? And where are we, contemporaneously, now? Is there a change in the definition with Rome IV? Maybe Bill can chime in on that also.

Brennan Spiegel, MD: Every few years some of us go to Rome. You know, we have a good time, we eat some pasta, and then we come down with some new criteria. But the human body doesn’t know that we’re coming up with new definitions for what it does. It just sort of keeps doing what it’s doing. So I think it’s important to have these definitions for academic purposes, for clinical trials, for example. But really, in the clinic, what Tony said is exactly right.

The idea is that you’re looking for people who have recurrent abdominal pain or discomfort, with abnormalities in stool frequency or form. And importantly, don’t have alarm features. They aren’t losing weight without trying and aren’t passing blood in their stool. These are signs that we call alarm signs, which would suggest maybe another diagnosis before we’re willing to make a diagnosis of IBS. But over the years, there have been many different definitions. Honestly, I don’t even think gastroenterologists have a clear handle on exactly how the definitions have evolved. I think that’s less important clinically than just understanding the basic phenotype, as we’ll get into what diagnostic tests may or may not be important.

Mark Pimentel, MD: The thing that confuses me the most about any of the criteria we have for IBS is the definition of pain. Because how often should it be? Should it be 5 minutes a day? Does that qualify as pain today? Or should it be an hour? Should it be 5 out of 10? For the clinician, for practical purposes, how do you use that particular symptom, Bill?

William D. Chey, MD: Before we talk about clinical practice, and just to clarify, the Rome criteria were originally developed as research criteria because we needed a common language to identify patients for clinical trials. We do go to Rome and eat pasta and drink wine. But honestly, it’s a comprehensive 5-year process to develop these criteria. I don’t want people to leave with the impression that we just sort of sit around the table and make this stuff up. No, it really is an evidence-based 5-year process to get to this product. But I agree with all the comments that have been made. In real life, we’re really probably not focusing on the Rome criteria. We’re really focusing on the presence of abdominal pain and altered bowel habits.

And to your specific question, Mark, the bottom line is that what’s meaningful is what’s meaningful to the patient. If they’re having problems for 5 minutes, but it’s interfering with their ability to carry out their daily activities, to me that’s meaningful.

Transcript edited for clarity.