A Paradigm Shift in Understanding Irritable Bowel Syndrome
Irritable bowel syndrome (IBS) is the most common functional gastrointestinal (GI) disorder in the United States and is defined as chronic abdominal pain associated with altered bowel habits (diarrhea, constipation, or mixed pattern). Subjects often describe additional GI symptoms including bloating, sensation of incomplete evacuation, straining (constipation), and urgency.
IBS prevalence is estimated to be 10-15 percent in Western countries, and it is recognized as the most common disorder in gastroenterology clinics and the second most common disorder in primary care practices, where the majority of IBS recognition and management occurs. IBS subjects may experience symptoms for many years prior to seeking medical advice, and it is estimated that only 25 percent of IBS sufferers even seek medical care. Those seeking care are often frustrated by the lack of effectiveness of traditional treatment and management strategies.
IBS places a significant financial burden on society. Symptoms can significantly impact quality of life of sufferers, with considerable socioeconomic consequences. For example, absenteeism from work is more prevalent in individuals with IBS than in those without, and employers in the United States are estimated to pay, on average, $1,251 more for individuals with IBS than matched control beneficiaries over a one-year period. Globally, quality of life is diminished in subjects with IBS who suffer silently and have high costs using multiple over-the-counter and prescription medications in an attempt to mitigate symptoms. IBS sufferers also have a higher risk of anxiety and depression, both of which can be escalated in the setting of incomplete control of gut symptoms, leading to a vicious cycle of lack of control over health, hypervigilance, drastic changes in lifestyle, and sense of hopelessness. Finally, there is a sense of isolation among sufferers who may have been told that symptoms are a sub-component of mental health issues and that symptoms are “all in your head” or due to “stress.” The perception among IBS subjects that their medical provider does not believe in the seriousness of their GI symptoms leads to a difficult dynamic with the health care system and a negative feeling that there is lack of validation for their illness.
The Rome Foundation provides guidance to practitioners about how to diagnose IBS. The Rome criteria are considered the gold standard for diagnosing functional GI disorders such as IBS and considered by experts as a highly accurate measure for making the diagnosis without the need for extensive endoscopic testing. The Rome criteria for IBS were developed over 25 years ago and revised in 2016 to reflect new research over the last decade that has provided great new insights into the pathophysiology of IBS. In general, the Rome Foundation has started to shift from defining IBS as a “functional GI disorder” and move towards defining it as a “disorder of brain-gut interaction.” Since a functional GI disorder has traditionally been defined as a disorder for which there is no known physiological or anatomical cause, the mainstay of diagnosing IBS relied on “ruling out” organic disorders like celiac disease and inflammatory bowel disease that may mimic IBS and have adjunct diagnostic testing to assist with making an accurate diagnosis. In light of new research in the past decade that has elucidated many new mechanisms for IBS, researchers and leaders in IBS want to move away from the misunderstanding that IBS is not real or has no underlying pathophysiological mechanism.
New research has led to enlightening findings that link IBS with immune dysfunction and microinflammation, alterations in the gut barrier function, food intolerances, changes in the gut microbiome including small intestinal bacterial overgrowth (SIBO), and gut-brain dysfunction mediated by stress hormones, serotonin, and the neuroendocrine and immune signaling between the brain, gut, and microbiome. These new interrelationships have led to a new area of research that ties together the gut-brain-microbiome axis. The axis is a complicated web of bi-directional flow that is facilitated by neural signaling, hormones, and the immune system.
Based on Rome IV criteria, IBS is defined as:
Recurrent abdominal pain, on average, at least one day per week in the last three months, associated with two or more of the following criteria:
- Related to defecation
- Associated with a change in frequency of stool
- Associated with a change in form (appearance) of stool
The criteria should be fulfilled for the last three months with symptom onset at least six months before diagnosis.
There are subtypes of IBS that include IBS-C (constipation predominant), IBD-D (diarrhea predominant), or IBS-M which is a mixed pattern (alternating diarrhea/constipation). IBS-M has also been called IBS-A (alternating). These subtypes were developed for research trials since symptom patterns vary considerably from one individual to another.
The new Rome IV criteria further highlight that the best management for functional GI disorders requires a biopsychosocial approach to care. This approach takes into consideration genetics, early life influences, psychosocial factors, stress, psychological state, social support, coping strategies, culture, and environment. From a pathophysiology standpoint, this involves incorporating concepts including gut motility, visceral hypersensitivity, immune function, gut barrier stability, the microbiome, and food. There is a renewed interest in understanding the metabolic intersection between food and gut function, and the role of food in immune dysfunction and microbiome alteration. Assessment and testing of the IBS patient should involve a careful assessment of psychological stress as a trigger for IBS activation and perpetuation, evaluation of the HPA axis intimately involved with the stress response, recognizing the importance of post-infectious causes of IBS, and analyzing clinically and with lab assessment dysbiosis (alteration in the gut microbiome) and its subsets including SIBO, yeast overgrowth, and depletion of beneficial bacteria.
The functional and integrative medicine approaches to managing functional GI disorders like IBS embrace the biopsychosocial model of care and also deliver on bringing the new science underlying IBS to the bedside with new testing and treatment opportunities. The functional medicine model seeks to determine “root cause” and incorporate treatment options in nutrition, mind-body medicine, and microbiome rehabilitation. This is in contrast with traditional gastroenterology approaches that have focused on invasive testing and pharmacologic therapies to mitigate (but not reverse) symptoms of disease. For IBS subjects who have experimented with multiple over-the-counter and prescription medications to mask symptoms, the “band aid approach” has led to a relapsing-remitting course without long-term resolution of underlying dysfunction. In functional medicine, the provider in partnership with the patient seeks to address root cause and reverse dysfunction as opposed to using short-term fixes that do not lead to long-term betterment.
Underlying mechanisms in IBS that are addressed in a functional medicine strategic plan include:
- Genetic polymorphisms, gene expression
- Stress, anxiety, depression
- Increased mucosal permeability
- Mucosal immune activation
- Food hypersensitivity, bile acid malabsorption
- Transient infection, altered and unstable microbiota
- Altered enteroendocrine metabolism
In a new paradigm shift, IBS is an umbrella for a wide range of new and emerging diagnoses that may be challenging to uncover but are now discovered with new approaches on the frontier of medicine.