Abstract
Irritable bowel syndrome (IBS) is a common cause of abdominal pain, affecting one in five adults in developed countries. Although it can also occur in the pediatric and adolescent population, the age of diagnosis is before the age of 50. Women are affected more frequently than men. IBS is characterized by recurrent abdominal pain, discomfort, bloating, gas, and an associated change in bowel habits that can take the form of either diarrhea or constipation. Often mucus is present in the stool. IBS is often classified as a functional gastrointestinal disorder because of the association with depression, gastrointestinal specific anxiety, alexithymia, mood disorders, sleep disorders, perimenstrual disorders, and sexual dysfunction. Food may serve as a trigger to IBS, with spices, chocolate, beans, cabbage, cruciferous vegetables, and fruits frequently implicated. Alterations in the gut microbiota, or dysbiosis, following antibiotic usage or gastrointestinal viral, bacterial, and parasitic infections may also contribute to the pathogenesis of IBS. There appears to be a genetic predisposition to IBS with a family history being identified in approximately 30% of patients diagnosed with IBS. It has been postulated that stress-induced alterations in the brain-gut axis affecting the central and autonomic nervous system, the enteric nervous system, and the neuroendocrine and neuroimmune systems play an important role in the evolution of this disease.
Keywords
irritable bowel syndrome, abdominal pain, diarrhea, constipation, functional bowel disease, lactose intolerance, celiac disease, colonoscopy
ICD-10 CODE
The Clinical Syndrome
Irritable bowel syndrome (IBS) is a common cause of abdominal pain, affecting one in five adults in developed countries. Although it can also occur in the pediatric and adolescent population, the diagnosis rarely occurs before the age of 50. Women are affected more frequently than men. IBS is characterized by recurrent abdominal pain, discomfort, bloating, gas, and an associated change in bowel habits that can take the form of either diarrhea or constipation ( Fig. 76.1 ). Often mucus is present in the stool. IBS is often classified as a functional gastrointestinal disorder because of the association with depression, gastrointestinal specific anxiety, alexithymia, mood disorders, sleep disorders, perimenstrual disorders, and sexual dysfunction. Food may serve as a trigger to IBS, with spices, chocolate, beans, cabbage, cruciferous vegetables, and fruits frequently implicated. Alterations in the gut microbiota, or dysbiosis, following antibiotic usage or gastrointestinal viral, bacterial, and parasitic infections may also contribute to the pathogenesis of IBS. There appears to be a genetic predisposition to IBS with a family history being identified in approximately 30% of patients diagnosed with IBS. It has been postulated that stress-induced alterations in the brain-gut axis affecting the central and autonomic nervous system, the enteric nervous system, and the neuroendocrine and neuroimmune systems play an important role in the evolution of this disease ( Fig. 76.2 ).
Testing
The diagnosis of irritable bowel syndrome is usually made by taking a careful history. The Rome Scoring Criteria for irritable bowel syndrome will help the clinician improve the specificity and sensitivity of diagnosis and guide the physical examination and the use of additional testing ( Table 76.1 ). Basic hematology, thyroid testing, and serum chemistries are indicated in all patients suspected of having IBS. Special attention to serum calcium to rule out hyperparathyroidism and thyroid function testing is mandatory. Stool analysis to rule all occult blood, malabsorption and viral, bacterial, and parasitic infections should also be performed. Fecal calprotectin analysis may help identify intestinal mucosal inflammation. Hydrogen glucose breath analysis and lactose intolerance testing to rule our bacterial overgrowth should be considered in those patients who developed abdominal symptoms following antibiotic therapy. Sigmoidoscopy, colonoscopy, and lower gastrointestinal barium studies may also be indicated to rule out diseases including inflammatory bowel diseases that may mimic IBS.
| Rome III Criteria | Rome IV Criteria |
|---|---|
| Adults | |
Recurrent abdominal pain or discomfort with onset at least 6 months prior to diagnosis, associated with 2 or more of the following, at least 3 days per month in the last 3 months
Children Abdominal discomfort or pain at least one per week, for at least 2 months before diagnosis, associated with 2 or more of the following at least 25% of time
No evidence of an inflammatory, anatomic, metabolic, or neoplastic process that explains the subject’s symptoms. Additional symptoms confirming the diagnosis:
| Recurrent abdominal pain with onset at least 6 months prior to diagnosis, associated with 2 or more of the following, at least 1 day per week in the last 3 months
Abdominal pain at least 4 days per months, for at least 2 months before diagnosis, associated with one or more of the following
In children with constipation, the pain does not resolve with resolution of the constipation (children in whom the pain resolves have functional constipation, not irritable bowel syndrome). After appropriate evaluation, the symptoms cannot be fully explained by another medical condition. |
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