Brian Lacy, MD, on Abdominal Distention and Bloating

In this podcast, Brian Lacy, MD, discusses the conditions that may cause abdominal distention and bloating, and the treatments available for each. 


Brian Lacy, MD, is a professor of medicine at Mayo Clinic Jacksonville, Jacksonville, Florida, coeditor of the American Journal of Gastroenterology, and Section Editor for Gastroenterology Learning Network's Stomach/Small Bowel Diseases section.




Gastroenterology Learning Network:  Hello, everyone. Welcome to another podcast from the Gastroenterology Learning Network. I'm managing editor Rebecca Mashaw. We're joined today by Dr. Brian Lacy of Mayo Clinic, Jacksonville, who is the section editor on the Gastroenterology Learning Network for stomach and small bowel diseases and disorders.

Dr. Brian Lacy:  Welcome. My name is Brian Lacy. I'm a professor of medicine at Mayo, Jacksonville. My clinical and research interests focus on topics that we call disorders of gut‑brain function, also called functional bowel disorders. That includes common topics including bloating, distention, irritable bowel syndrome, gastroparesis, function dyspepsia, and constipation.

GLN:  Thank you so much for joining us today, Dr. Lacy. We're going to be talking about those first 2 topics of abdominal distention and bloating. You recently published a paper on this. You and your coauthors mentioned that they're among the most common GI disorders that you see in the clinic. What do we know about what causes bloating and distention? Can you distinguish between the two?

Dr. Lacy:  Lots of great questions buried into one. On the one hand, I'd like to say that we know an awful lot, and on the other hand, I'm going to say we know very little. What I mean by that is that these are prevalent symptoms, that of bloating and distention.

If we survey the general population, up to 50% of the general population will say that during the course of the month, they have problems with bloating and distention. In some populations, such as those with irritable bowel syndrome, or IBS, in many research studies, it may be as high as 90%.

We've identified too that in other disorders of the GI tract, such as what we call functional dyspepsia, or chronic constipation, or small intestinal bacterial overgrowth, or gastroparesis, bloating symptoms are also quite common. In terms of ideology, it gets tricky. What's really the cause? This is where we really need to know more.

We believe that in some patients it may be genetic. We could think about somebody who genetically is predisposed to have these symptoms. Maybe genetically they're predisposed to not digest carbohydrates properly. In other people, it may reflect prior surgery, and surgery to the small intestine or colon can cause these problems.

It may reflect a lot of prior antibiotic use or medications that can change your gut microbiome, and thus, you process foods differently. In other patients, it may relate to some prior infection in the GI tract, or trauma, or stress. Although we know a lot about it, sometimes in an individual patient it's hard to explain why those symptoms developed.

GLN:  You mentioned that about 50% to 60% of patients report abdominal distention or bloating. They're often thought to be the same thing; however, there really is a distinction, according to your paper. Can you explain a little about the difference and how a patient might have one without the other?

Dr. Lacy:  Absolutely. Many providers do lump all these terms together in terms of gas, and bloating, and distention. However, they actually are distinct. Bloating is a sensation of gassiness. Patients will tell me they feel full and they'll point to their upper belly. They'll say they feel like they have a balloon inside of them. It's that sensation of gassiness, and it really is a sensory disorder.

In contrast, distention is the physical manifestation. Patients will come in, they'll point to their belly. They say they look 6 or 8 months pregnant. Maybe they've taken photos at home— everybody loves to do this—and they bring in their smartphone to show me how distended they look.

When I think about bloating, it's really a sensation of gassiness. Distention is a physical manifestation. Now, oftentimes, they exist separately, but frequently, they overlap. They may reflect different underlying pathophysiologies.

GLN:  Arriving at a diagnosis in some of these cases sounds like it could be a pretty lengthy and complex process. If a patient walks in complaining of bloating and/or distention, where do you start? What should a gastroenterologist do first?

Dr. Lacy:  Great. This is where, as clinicians, whether you're in the primary care doctor's office, a gastroenterologist, surgeon, an OB/GYN doctor, you need to put on your thinking cap. One approach is just try to memorize a list of 100 different things that can cause bloating and distention, but that's an awful lot of work and not very effective.

I like to think about the 3 major pathophysiological processes. The way I think about it is, there is a group of disorders that cause stretching and distention of the small bowel or colon causing bloating or distention.

That usually includes things like carbohydrate intolerance, lactose, fructose intolerance, eating foods high in FODMAPs —fermentable oligosaccharides, disaccharides, and monosaccharides. It also includes small intestinal bacterial overgrowth.

The second big category are those where patients report symptoms of bloating because they're so sensitive. A misconception is that patients with bloating and distention produce more gas than anybody else. That's oftentimes not true. That middle category, that of sensory disorder, is because people sense small amounts and normal amounts of gas too well. These are patients who frequently have other disorders of sensation. They may have IBS. They may have migraine headaches. They have chronic fatigue, or fibromyalgia, or interstitial cystitis. They are just sensitive.

The last group is the least common. That's patients who have really a wiring problem. Small amounts of gas can trigger an abnormal reflex. Now, I have to explain the normal first. The normal is we all have some gas in the GI tract and a small amount of stretch or distention. When that occurs, normally, your diaphragm ascends, comes up into your chest. That enlarges the abdominal cavity to accommodate that gas. In addition, your abdominal wall muscles contract to keep your belly flat. That's a normal reflex. Some people actually are miswired, and instead of those two things occurring, your diaphragm descends inappropriately.

That now makes your abdominal cavity smaller. You can't accommodate that gas and your abdominal wall muscles relax, so your belly kind of pouches out. That's called an abnormal viscerosomatic reflex.

GLN:  Some of these factors come into play when you talk about people who have, for instance, a carbohydrate intolerance but don't necessarily have a malabsorption. For instance, someone who's lactose intolerant, they don't always become symptomatic after they ingest lactose. Is that correct?

Dr. Lacy:  Absolutely. Lactose intolerance is a great example of carbohydrate intolerance. What we would assume is that symptoms predict the level of lactase deficiency. Remember, lactose is a disaccharide, 2 sugar molecules hooked together, glucose and galactose. We all have lactase when we're born, on our small intestine, an enzyme to break it down.

However, as we get older, many of us lose it. As a matter of fact, of adult Caucasians, about 35% are lactase deficient. That's higher in Asian populations. It may be as high as 90% to 95%. What you're highlighting is that some people can ingest milk even if they're lactase deficient and not have symptoms. Why would that be?

One, it may depend upon the level of lactase deficiency. Some people lose all their lactase, some just some. There may be a threshold of how much lactose they could take in, and milk products. In addition, think about that patient who is sensitive on the inside as well, and they have IBS and dyspepsia, and interstitial cystitis, that sensory problem in the bladder.

Even small amounts of lactose, even if they can break down that small amount may cause distress, gurgling, churning, cramps, spasms, and pain because they're extra sensitive. It's always not just the amount of lactase enzyme, there are lots of other factors as well. How do they respond to that milk sugar?

GLN:  What kind of treatments are available for these conditions?

Dr. Lacy:  Let's go back and let's think about those 3 big categories as well. When I think about that first category of bloating and distention, is it related to diet or possibly bacterial overgrowth, or constipation? If I think it's diet, I'm going to think about the worst offenders. Is it dairy? Is it fructose intolerance? Is it those, what we call FODMAPs, fermentable oligosaccharides, disaccharides, and monosaccharides? Because they create a lot of gas and distention. Might they have bacterial overgrowth? We can check that with a breath test. Are they severely constipated? If we can improve their constipation, gas and bloating gets better. That's 1 category.

As we take the history and do the exam, are they that patient who is just so sensitive to everything? They have IBS, and dyspepsia, and those disorders of somatic sensitivity— fibromyalgia, migraine headaches, interstitial cystitis. They are the ones who are likely sensing small amounts or normal amounts of gas abnormally. They might responds to medicines that help block sensory thresholds down, such as gabapentin, or older antidepressants called tricyclic antidepressants, or medicines called SNRIs that act on the serotonin‑norepinephrine system.

Then finally, there is that last group, the smaller group, who have this horrible amount of distention that may be this wiring problem, this visceroabdominal reflex that's abnormal. Those patients do great with diaphragmatic breathing. You can actually teach them how to breath more normally to allow their belly to expand to accommodate that gas as opposed to having this abnormal wiring problem.

GLN:  That's very interesting. You have training to teach patients how to breathe so that they can alleviate those symptoms?

Dr. Lacy:  It seems funny that a gastroenterologist would have the training, so I've learned how to teach it. The answer is yes. Actually, some of the best teachers are professional singers because they know how to breathe properly. In the past, I would sometimes send them to an opera singer I knew who lived nearby our hospital who could teach them.

We now have behavioral therapists, but I can teach them. It's a simple hand on chest, hand on belly mechanism, but there are some great YouTube videos now, and there is some great offerings from the American College of Gastroenterology, so patients can actually learn from me in the office but then go home and practice this. For many patients, it's really just a godsend.

GLN:  What do you think the future holds in this area? Clearly, some additional research may be needed to help clarify the causes, simplify diagnostic procedures, maybe more effective treatments. Where do you see things heading?

Dr. Lacy:  Lots of opportunities. I think the opportunities include, can we do a better job diagnosing it? Are there some simple office tests we could do to quickly distinguish those 3 categories I've mentioned, and could there be better treatment? We've learned a lot from those diaphragmatic breathing. That's great, but could we do better in terms of other treatments? Possibly different types of antibiotics or probiotics, or different types of medicines to quiet down the sensory tract and the GI tract. There is a wealth of opportunities for these very common symptoms that are just so bothersome to patients.

GLN:  Well, this has been a very interesting conversation. I really appreciate your time today and your insight into this subject. We look forward to talking with you again.

Dr. Lacy:  Great. Well, thank you so much. Thank you to our listeners today. This is a lot of fun.