Understanding a Common Yet Misunderstood Condition

Irritable bowel syndrome (IBS) is one of the most common conditions encountered by both primary care providers and gastroenterologists, with a pooled global prevalence of 11.2%. This functional bowel disorder is characterized by abdominal pain or discomfort, diarrhea and/or constipation, and bloating.

Unfortunately, IBS is often misunderstood or minimized by some healthcare professionals, according to Alan Desmond, MB, consultant in gastroenterology and general internal medicine, Torbay Hospital, Torquay, UK National Health Service, England.

Desmond regularly sees patients who either haven’t been accurately diagnosed or have been told, “Don’t worry, it’s ‘just’ irritable bowel syndrome,” he said at the recent International Conference on Nutrition in Medicine.

A 2017 study involving nearly 2000 patients with a history of gastrointestinal (GI) symptoms found that 43.1% of those who met the criteria for IBS were undiagnosed, and among those who were diagnosed, 26% were not receiving treatment.

“Many clinicians vastly underestimate the impact functional GI symptoms have on our patients in lack of productivity, becoming homebound or losing employment, the inability to enjoy a meal with friends or family, and always needing to know where the nearest bathroom is, for example,” Desmond told Medscape Medical News.

IBS can profoundly affect patients’ mental health. One study found that 38% of patients with IBS attending a tertiary care clinic contemplated suicide because they felt hopeless about ever achieving symptom relief.

Today, several dietary, pharmacologic, and psychological/behavioral approaches are available to treat patients with IBS, noted William Chey, MD, chief of the Division of Gastroenterology and Hepatology, University of Michigan, Ann Arbor, Michigan.

“Each individual patient may need a different combination of these foundational treatments,” he said. “One size doesn’t fit all.”

Diagnostic Pathway

One reason IBS is so hard to diagnose is that it’s a “symptom-based disorder, with identification of the condition predicated upon certain key characteristics that are heterogeneous,” Chey told Medscape Medical News. “IBS in patient ‘A’ may not present the same way as IBS in patient ‘B,’ although there are certain foundational common characteristics.”

IBS involves “abnormalities in the motility and contractility of the GI tract,” he said. It can present with diarrhea (IBS-D), constipation (IBS-C), or a mixture or alternation of diarrhea and constipation (IBS-M).

Patients with IBS-D often have an exaggerated gastro-colonic response, while those with IBS-C often have a blunted response.

Beyond stool abnormalities and abdominal pain/discomfort, patients often report bloating/distension, low backache, lethargy, nausea, thigh pain, and urinary and gynecologic symptoms.

Historically, IBS has been regarded as a “diagnosis of exclusion” because classic diagnostic tests typically yield no concrete findings. Desmond noted that several blood tests, procedures, imaging studies, and other tests are available to rule out other organic GI conditions, as outlined in the Table.

Table. Tests to Rule Out Other Organic GI Conditions

Courtesy of Alan Desmond, MB

If the patient comes from a geographical region where giardia is endemic, clinicians also should consider testing for the parasite, Chey said.

New Understanding of IBS Etiology

Now, advances in the understanding of IBS are changing the approach to the disease.

“The field is moving away from seeing IBS as a ‘wastebasket diagnosis,’ recognizing that there are other causes of a patient’s symptoms,” Mark Pimentel, MD, associate professor of medicine and gastroenterology, Cedars-Sinai, Los Angeles, told Medscape Medical News. “What’s made IBS so difficult to diagnose has been the absence of biological markers and hallmark findings on endoscopy.”

Recent research points to novel bacterial causes as culprits in the development of IBS. In particular, altered small bowel microbiota can be triggered by acute gastroenteritis.

Food poisoning can trigger the onset of IBS — a phenomenon called “postinfectious IBS (PI-IBS),” said Pimentel, who is also executive director of the Medically Associated Science and Technology Program at Cedars-Sinai. PI-IBS almost always takes the form of IBS-D, with up to 60% of patients with IBS-D suffering the long-term sequelae of food poisoning.

The types of bacteria most commonly associated with gastroenteritis are Shigella, Campylobacter, Salmonella, and Escherichia coli, Pimentel said. All of them release cytolethal distending toxin B (CdtB), causing the body to produce antibodies to the toxin.

CdtB resembles vinculin, a naturally occurring protein critical for healthy gut function. “Because of this molecular resemblance, the immune system often mistakes one for the other, producing anti-vinculin,” Pimentel explained.

This autoimmune response leads to disruptions in the gut microbiome, ultimately resulting in PI-IBS. The chain of events “doesn’t necessarily happen immediately,” Pimentel said. “You might have developed food poisoning at a party weeks or months ago.”

Acute gastroenteritis is common, affecting as many as 179 million people in the United States annually. A meta-analysis of 47 studies, incorporating 28,270 patients, found that those who had experienced acute gastroenteritis had a fourfold higher risk of developing IBS compared with nonexposed controls.

“The problem isn’t only the IBS itself, but the fact that people with PI-IBS are four times as likely to contract food poisoning again, which can further exacerbate IBS symptoms,” Pimentel said.

Diarrhea-predominant IBS can be detected through the presence of two blood biomarkers — anti-CdtB and anti-vinculin — in a blood test developed by Pimentel and his group.

“Elevation in either of these biomarkers establishes the diagnosis,” Pimentel said. “This is a breakthrough because it represents the first test that can make IBS a ‘diagnosis of inclusion.’”

The blood test also can identify IBS-M but not IBS-C.

Pimentel said that IBS-C is associated with increased levels of methanogenic archaea, which can be diagnosed by a positive methane breath test. “Methane gas slows intestinal contractility, which might result in constipation,” he said.

Diet as a Treatment Option

Diet is usually the starting point for IBS treatment, Chey said. “The standard dietary recommendations, as defined by the National Institute for Health and Care Excellence Guidance for managing IBS, are reasonable and common sense — eating three meals a day, avoiding carbonated beverages, excess alcohol, and excess caffeine, and avoiding hard-to-digest foods that can be gas producing.”

A diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs), which are carbohydrates that aren’t completely absorbed in the intestines, has been shown to be effective in alleviating GI distress in as many as 86% of patients with IBS, leading to improvements in overall GI symptoms as well as individual symptoms (eg, abdominal pain, bloating, constipation, diarrhea, and flatulence).

Desmond recommends the low FODMAP program delineated by Monash University in Australia. The diet should be undertaken only under the supervision of a dietician, he warned. Moreover, following it on a long-term basis can have an adverse impact on dietary quality and the gut microbiome. Therefore, “it’s important to embark on stepwise reintroduction of FODMAPS under supervision to find acceptable thresholds that don’t cause a return of symptoms.”

A growing body of research suggests that following the Mediterranean diet can be helpful in reducing IBS symptoms. Chey said that some patients who tend to over-restrict their eating might benefit from a less restrictive diet than the typical low FODMAPs diet. For them, the Mediterranean diet may be a good option.

Pharmacotherapy for IBS

Nutritional approaches aren’t for everyone, Chey noted. “Some people don’t want to be on a highly restricted diet.” For them, medications addressing symptoms might be a better option.

Antispasmodics — either anticholinergics (hyoscine and dicyclomine) or smooth muscle relaxants (alverine, mebeverine, and peppermint oil) — can be helpful, although they can worsen constipation in a dose-dependent manner. It is advisable to use them on an as-needed rather than long-term basis.

Antidiarrheal agents include loperamide and diphenoxylate.

For constipation, laxatives (eg, senna, bisacodyl, polyethylene glycol, and sodium picosulphate) can be helpful.

Desmond noted that the American Gastroenterological Association does not recommend routine use of probiotics for most GI disorders, including IBS. Exceptions include prevention of Clostridioides difficile, ulcerative colitis, and pouchitis.

Targeting the Gut-Brain Relationship

Stress plays a role in exacerbating symptoms in patients with IBS and is an important target for intervention.

“If patients are living with a level of stress that’s impairing, we won’t be able to solve their gut issues until we resolve their stress issues,” Desmond said. “We need to calm the gut-microbiome-brain axis, which is multidimensional and bidirectional.”

Many people — even those without IBS — experience queasiness or diarrhea prior to a major event they’re nervous about, Chey noted. These events activate the brain, which activates the nervous system, which interacts with the GI tract. Indeed, IBS is now recognized as a disorder of gut-brain interaction, he said.

“We now know that the microbiome in the GI tract influences cognition and emotional function, depression, and anxiety. One might say that the gut is the ‘center of the universe’ to human beings,” Chey said.

Evidence-based psychological approaches for stress reduction in patients with IBS include cognitive behavioral therapy, specifically tailored to helping the patient identify associations between IBS symptoms and thoughts, emotions, and actions, as well as learning new behaviors and engaging in stress management. Psychodynamic (interpersonal) therapy enables patients to understand the connection between GI symptoms and interpersonal conflicts, emotional factors, or relationship difficulties.

Gut-directed hypnotherapy (GDH) is a “proven modality for IBS,” Desmond said. Unlike other forms of hypnotherapy, GDH focuses specifically on controlling and normalizing GI function. Studies have shown a reduction of ≥ 30% in abdominal pain in two thirds of participants, with overall response rates up to 85%. It can be delivered in an individual or group setting or via a smartphone.

Desmond recommends mindfulness-based therapy (MBT) for IBS. MBT focuses on the “cultivation of mindfulness, defined as intentional, nonjudgmental, present-focused awareness.” It has been found effective in reducing flares and the markers of gut inflammation in ulcerative colitis, as well as reducing symptoms of IBS.

Chey noted that an emerging body of literature supports the potential role of acupuncture in treating IBS, and his clinic employs it. “I would like to see further research into other areas of CAM [complementary and alternative medicine], including herbal approaches to IBS symptoms as well as stress.”

Finally, all the experts agree that more research is needed.

“The real tragedy is that the NIH invests next to nothing in IBS, in contrast to inflammatory bowel disease and many other conditions,” Pimentel said. “Yet IBS is 45 times more common than inflammatory bowel disease.”

Pimentel hopes that with enough advocacy and recognition that IBS isn’t “just stress-related,” more resources will be devoted to understanding this debilitating condition.

Desmond is the author of a book on the benefits of a plant-based diet. He has also received honoraria, speaking, and consultancy fees from the European Space Agency, Dyson Institute of Engineering and Technology, Riverford Organic Farmers, Ltd., Salesforce, Inc., Sentara Healthcare, Saudi Sports for All Federation, the Physicians Committee for Responsible Medicine, The Plantrician Project, Doctors for Nutrition, and The Happy Pear.

Pimentel is a consultant for Bausch Health, Ferring Pharmaceuticals, and Ardelyx. He holds equity in and is also a consultant for Dieta Health, Salvo Health, Cylinder Health, and Gemelli Biotech. Cedars-Sinai has a licensing agreement with Gemelli Biotech and Hobbs Medical.

Chey is a consultant to AbbVie, Ardelyx, Atmo, Biomerica, Gemelli Biotech, Ironwood Pharmaceuticals, Nestle, QOL Medical, Phathom Pharmaceuticals, Redhill, Salix/Valeant, Takeda, and Vibrant. He receives grant/research funding from Commonwealth Diagnostics International, Inc., US Food and Drug Administration, National Institutes of Health, QOL Medical, and Salix/Valeant. He holds stock options in Coprata, Dieta Health, Evinature, FoodMarble, Kiwi Biosciences, and ModifyHealth. He is a board or advisory panel member of the American College of Gastroenterology, GI Health Foundation, International Foundation for Gastrointestinal Disorders, Rome. He holds patents on My Nutrition Health, Digital Manometry, and Rectal Expulsion Device.

Batya Swift Yasgur, MA, LSW, is a freelance writer with a counseling practice in Teaneck, NJ. She is a regular contributor to numerous medical publications, including Medscape and WebMD, and is the author of several consumer-oriented health books as well as Behind the Burqa: Our Lives in Afghanistan and How We Escaped to Freedom (the memoir of two brave Afghan sisters who told her their story).