Irritable bowel syndrome (IBS) is the most commonly diagnosed gastrointestinal disorder. The underlying symptoms of the disease are abdominal pain or discomfort with altered bowel habits that are not caused by other diseases. A recent clinical review of irritable bowel syndrome was published in the journal JAMA, covering the epidemiology, natural course, pathophysiology, diagnosis and management of IBS. Medical Pulse has compiled the following.
The pooled population-based prevalence of IBS varies globally, in part related to differences in investigators, diagnostic criteria, and study methods. The population-based prevalence of IBS in North America is approximately 12%. IBS is most prevalent in South America (21%) and least prevalent in Southeast Asia (7.0%). The prevalence of IBS symptoms in women is 1.5 to 2 times higher than in men in the United States, Canada, and Israel, while Asian men and women are more equally affected. Among the reported symptom presentations, abdominal pain and constipation were more common in women and diarrhea was more common in men. The prevalence of IBS decreases with age. In the United States, diarrheal IBS (IBS-D), constipated IBS (IBS-C), and mixed IBS (IBS-M) were equally distributed, whereas in Europe, IBS-C or IBS-M were more common.
Disease burden and natural course
Multiple comorbidities are associated with IBS, including trunk pain syndromes (fibromyalgia, chronic fatigue syndrome, and chronic pelvic pain), other gastrointestinal disorders (GERD and dyspepsia), and psychiatric disorders (major depression, anxiety, and somatization) that increase the likelihood of co-morbidity.
In most patients, IBS is a chronic relapsing disease, with symptoms changing over time. A systematic review showed that during long-term follow-up of patients with outpatient-based IBS, 2% to 18% of patients worsened, 30% to 50% remained unchanged, and 12% to 38% improved. Undergoing surgery early, prolonged disease duration, higher torso scores, and comorbid anxiety and depression predict a poorer IBS prognosis.
Over time, patients may migrate between different IBS subtypes, most commonly from IBS-C or IBS-D to IBS-M; transitions between IBS-C and IBS-D occur less frequently. Many studies of the “natural course” of IBS are influenced by the treatment introduced by the patient or physician. Therefore, it is difficult to know whether changes in symptoms are the result of pharmacological interventions or the true natural course of IBS.
IBS significantly reduces people’s health-related quality of life and ability to work. 13 to 88% of people with IBS seek medical treatment. Individuals who seek medical care experience more distress and lack social support than those who do not. In the United States, IBS accounts for 3.1 million outpatient visits, 5.9 million prescriptions written, and over $20 billion in indirect and direct expenditures annually.
Pathophysiology
IBS pathogenesis, such as the clinical phenotype, is heterogeneous (Table 1). At the end of the last 40 years, IBS may include a large number of different pathophysiologic disorders while presenting with similar symptoms, and many factors have now emerged to help identify the pathophysiologic mechanisms of IBS. Traditionally, the pathogenesis of IBS has focused on abnormalities in peristalsis, visceral sensation, brain-gut interactions, and psychological stress. Although one or more abnormalities are demonstrable in most patients with IBS, none can explain the symptoms in all patients. Recently, alterations in intestinal immune activation, intestinal permeability, and small intestinal and colonic microbes have been identified in certain IBS patients.
Diagnosis
The diagnosis of IBS is based on the presence of characteristic symptoms, excluding selected organic diseases (Table 2). According to the current diagnostic criteria, Rome III criteria, the main features of IBS include abdominal pain or discomfort, and altered bowel habits (Table 3).
Although identifying patients with IBS-D or IBS-C is straightforward, identification of patients with IBS-M remains challenging. A detailed history helps to identify is all for a mixed bowel pattern that can indicate an underlying disease state or the result of pharmacologic intervention. It is important to consider all prescription and OTC medications, as well as supplements, that may affect IBS symptoms (Table 4). Many IBS patients report that a bowel diary helps identify patterns of disordered bowel habits.
Management
General management recommendations
A mutually trusting doctor-patient relationship is the cornerstone of managing patients with IBS. Active listening, noninterruption, a sympathetic tone, and setting realistic expectations (“help” rather than “cure”), along with nonverbal techniques such as eye contact, nodding, leaning forward, and open body gestures, can help establish a good patient-physician relationship. Clinicians must understand the goals of the patient’s visit and avoid focusing on gastrointestinal symptoms. Conducting a physical exam helps establish a bond, which allows many patients to get to know their physician fully and completely. Giving the patient a confident diagnosis while providing an IBS-related etiology, natural history, and treatment is essential to treatment.
Because IBS is a symptom-based disease, treatment can address abdominal symptoms such as pain, cramping, bloating, or bowel symptoms, including diarrhea and constipation (Table 2). Traditionally, first-line IBS treatment has focused on OTC medications designed to improve diarrhea (e.g., loperamide, probiotics) or constipation (e.g., fiber supplements, laxatives). The advantages of this treatment are improved bowel habits, widespread use, low cost, and a good safety record. However, OTC medications have low benefit for overall IBS symptoms or abdominal symptoms (e.g., pain and bloating). The table summarizes IBS treatment, as well as recent recommendations and quality of evidence assessments published from the American College of Gastroenterology Functional Bowel Disease Task Force. Over the past 5 years, lifestyle and dietary interventions have become increasingly important first-line treatment options.
Exercise
Individuals who are physically active have more frequent bowel movements and a more rapidly functioning colon than those who are sedentary. In addition, a randomized clinical trial found that a structured exercise intervention resulted in greater improvement in overall IBS symptoms than usual treatment. Therefore, patients with IBS should be encouraged to increase their physical activity. A simple recommendation is to walk 20 minutes (approximately 1 mile) per day. The distance and pace can be increased gradually as tolerated.
Diet
Symptoms in patients with IBS are often related to diet. Up to 90 percent of people with IBS have to restrict their diet to prevent or improve symptoms. True allergies to things are rare in IBS. On the other hand, things intolerances or sensitivities are frequently reported in cases. Currently, evidence is developing to support a gluten-free diet for patients with IBS that is also low in fermented oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP).
Medication (as indicated in the table)
Summary
In summary, the diagnosis of IBS relies on the identification of characteristic symptoms and the exclusion of other organic pathologies, and the management of patients with IBS can be optimized through an individualized, comprehensive approach that encompasses multiple aspects of diet, lifestyle, pharmacotherapy, and behavioral interventions.