Irritable Bowel Syndrome (IBS)

Introduction

Irritable bowel syndrome (IBS) is the most common of the functional gastrointestinal (GI) disorders that affect the large intestine. IBS is considered a chronic disorder characterized by intermittent abdominal pain or discomfort associated with altered bowel movement for at least three months. IBS is also considered a disorder of gut-brain interactions as it is related to how the brain and gut work together. The gut becomes more sensitive and changes how the bowel muscle contract leading to abdominal pain, bloating, diarrhea, constipation, or a combination of diarrhea and constipation. Even with these troublesome symptoms, IBS is not a life-threatening condition, however; it could intensely change the quality of life and work productivity. The prevalence of IBS varies throughout the world. It ranges from 10% to 23% in the general population worldwide, with the highest prevalence of 21% in South America and the lowest prevalence of 4.2% in South Africa. In the Arab region, the prevalence of IBS is ranged from 8.9% to 31.8%. In Saudi Arabia, the prevalence of IBS was 22.9% (Alosaim M., Ali A., & H., 2016). The prevalence of IBS is higher in women than men by a 2:1 ratio. Younger people are more likely to develop IBS than people older than 50 years. This disorder is classified into four subtypes, each with slightly different symptoms, depending on the bowel habits (stool type and frequency). These subtypes include irritable bowel syndrome constipation-predominant (IBS-C), irritable bowel syndrome diarrhea-predominant (IBS-D), irritable bowel syndrome mixed (IBS-M), and irritable bowel syndrome unspecified (IBS-U). To distingue between these classifications of IBS, health care provider would investigate how stool type (watery vs. solid) and frequency (number of times) change in response of abdominal pain (a common symptom in this disorder). (Chey, Kurlander, & Eswaran, 2015; Lacy et al., 2016; Moayyedi et al., 2017).

The precise cause of IBS remains unknown; however, several factors have been linked to increasing the risk of IBS. These include lifestyle factors such as diet, smoking, and alcohol consumption; psychological factors such as stress and anxiety; genetic factors; small intestinal bacterial overgrowth; food intolerance as well as severe infection in the GI system. Although the pathophysiology is not entirely recognized, understanding the pathogenesis of IBS is vital in developing newer pharmacotherapy agents to target the known pathophysiologic mechanisms. The pathogenesis of the IBS is complex and multifactorial. Several pathophysiological abnormalities have been described, including altered gastrointestinal motility, increased sensitivity of the GI tract to internal and external stimuli, disturbances of brain-gut interactions, food intolerance, bacterial overgrowth, post-infectious reactivity, dysregulation of serotonin concentrations in the GI tact, genetic susceptibility, and psychosocial stress factors. Nervous system alterations can result in abnormal gastrointestinal motility and visceral hypersensitivity. Researchers found that concentrations of serotonin are associated with IBS. Low serotonin concentrations are associated with constipation whereas higher serotonin concentrations are associated with diarrhea (Academy of Nutrition and Dietetics, 2020; Alharbi, 2018; Canadian Society of Intestinal Research, 2018; Cedars-Sinai, 2020; Chey et al., 2015; Lacy et al., 2016; Lehrer, J. K., 2019; Mayo Clinic, 2018; Peyton & Greene, 2014; WebMD, 2020).