IMPORTANT NOTE: JAAPA CME activities consist of 2 articles. To obtain credit, you must also read
Neuroblastoma: Management of a
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Key Points
■ Irritable bowel syndrome (IBS) is defined as abdominal pain and altered bowel habits in the absence of an organic explanation. IBS can be further categorized as diarrhea-predominant (IBS-D), constipation-predominant (IBS-C), or mixed-type (IBS-M).
■ No single etiology has been determined, but causation theories include errors in GI tract motility, alterations in autonomic regulation, increased visceral sensitivity, abnormal brain-gut interaction, and flora changes.
■ No specific marker or test is diagnostic for IBS. CBC, serum chemistry analysis, thyroid function studies, and colonoscopy are recommended for patients with alarm symptoms. Serologic testing for celiac sprue may be necessary for patients with IBS-D and IBS-M, particularly those who have noticed having difficulty when eating gluten products in the past.
■ Patients with IBS should be educated that while their condition is not life threatening, it may be lifelong. Both clinician and patient should understand that no single therapy has been proven to provide relief for all patients.
Irritable bowel syndrome (IBS) is often discussed but frequently misunderstood. It is defined as abdominal pain and altered bowel habits in the absence of an organic explanation. Irritable bowel syndrome can be further categorized as diarrhea-predominant (IBS-D), constipation-predominant (IBS-C), or mixed-type (IBS-M). Irritable bowel syndrome is one of the most common conditions seen by physicians, and IBS is the reason for 3.7 million office visits per year, an estimated 12% of primary care appointments.1,2 Its impact on daily life can be substantial, interrupting work, finances, and personal relationships. Better comprehension and improved control of IBS symptoms are clearly necessary.
Prevalence of IBS in the United States is reported to range from 10% to 22%,1,3 with a worldwide prevalence of 10% to 15%.4 IBS is estimated to be up to 2 times more common in women than men; but in some countries, such as India, it predominates in men.5,6 Irritable bowel syndrome is typically diagnosed at age 20 to 50 years; however, many patients recall similar GI symptoms during childhood.2,7 Patients with the condition are more likely to have higher levels of stress; lower socioeconomic status; and psychological conditions such as anxiety and depression.2,5 Data suggest that IBS-D and IBS-M are more common than IBS-C.5
ETIOLOGY
Irritable bowel syndrome was initially believed to be a product of psychological problems; however, evidence now indicates that IBS results from physiologic changes. No single etiology has been determined, but causation theories include errors in GI tract motility, alterations in autonomic regulation, increased visceral sensitivity, abnormal brain-gut interaction, and flora changes.
The colon delays transit of feces, allowing time for absorption of approximately 90% of the fluid present from the ileum.8 Altered motility of the GI tract leads to changes in fecal consistency. If transit occurs too fast, not enough water will be absorbed, resulting in diarrhea. If transit slows, too much water is absorbed and constipation occurs. The gastrocolic reflex (the increase in intestinal peristalsis and motility that follows eating) is believed to be overactive in patients with IBS-D. Numerous studies have shown that visceral hypersensitivity, or a heightened sensitivity to intestinal activity, is common in many patients with IBS.9,10
A hypothesis of IBS etiology is that it manifests secondary to abnormal regulation of the CNS, immune system, and enteric nervous system (ENS).7 The ENS, composed of a high concentration of neurotransmitters and nerves that line the GI tract, controls motility, secretions, and fluid transport in the bowel.6 Approximately 90% of serotonin is found in the gut alone, and blocking serotonin in the GI tract has been shown to decrease visceral pain and transit time.7 Serotonin receptors also play a role in controlling the absorption and secretion of fluid.5 Modifications in the components of the enteric nervous system can lead to increased sensitivity to abdominal distention and environmental factors, as well as altered transit time.5,6 Furthermore, these changes may persist for extended periods of time.
Bacterial imbalance is another factor that may impact intestinal function. Under normal conditions, intestinal flora provides nutrition to the host, moderates the mucosal immune system, and regulates epithelial growth and function.8,11 Some researchers believe that small intestinal bacterial overgrowth (SIBO) may contribute to IBS. SIBO prevalence in patients with IBS is reported to be 38% to 84%, but many of these studies had poor qualifications and did not have the same results when repeated.12,13 Whether SIBO is directly connected to IBS or is a separate entity remains unclear.