Irritable bowel syndrome

Disease Description (Causes and Symptoms)

• Definition summary: A functional bowel disorder (irritable bowel syndrome, IBS) characterized by chronic abdominal pain and bowel dysfunction that cannot be explained by organic (structural) abnormalities.
• Pathophysiology (summary): A combination of visceral hypersensitivity, abnormal intestinal motility (diarrhea, constipation, or a mixed pattern), intestinal microbiota imbalance (SIBO in some patients), and abnormalities of the gut–brain axis (interactions with emotions and stress) contributes to the condition.
• Main symptoms:
  • Recurrent abdominal pain (tending to improve after bowel movements)
  • Diarrhea (IBS-D), constipation (IBS-C), or repeated occurrence of both patterns (IBS-M)
  • Mucus in the stool, abdominal bloating, and excessive gas
  • Fatigue, headache, sleep problems, and possible accompanying upper gastrointestinal symptoms (such as heartburn)
• Caution: Weight loss, bloody stool, anemia, or new symptoms in people aged 50 or older are “warning signs” requiring additional testing to distinguish organic diseases.

Treatment Methods

• Basic principles: Patient education (understanding the condition), lifestyle and dietary modification, symptom-specific medication, and psychological or behavioral therapy when needed.
• Lifestyle and dietary measures:
  • Eat regular meals and limit overeating, excessive fat, and irritating foods (spicy foods, caffeine, and alcohol)
  • Dietary fiber: May provide temporary improvement, but excessive intake can worsen bloating — soluble fiber (e.g., psyllium) is recommended over insoluble fiber
  • A low-FODMAP diet may be helpful (try it short term, followed by gradual reintroduction; consultation with a dietitian is recommended)
  • Stress management (exercise, sleep, meditation, etc.)
• Medication therapy (by symptoms and type):
  • Abdominal pain/cramps: Antispasmodics (e.g., hyoscine, dicyclomine; available medications vary by country), and low-dose tricyclic antidepressants (TCAs, such as amitriptyline) — useful for pain control
  • Diarrhea-predominant type (IBS-D): loperamide (antidiarrheal), rifaximin (a selective intestinal antibiotic, considered when SIBO is suspected), bile acid sequestrants (when bile acid diarrhea is suspected), and eluxadoline (check the risk of pancreatitis and restrictions before use)
  • Constipation-predominant type (IBS-C): Dietary fiber and bulk-forming laxatives (psyllium), osmotic laxatives (PEG), prucalopride (check availability in the relevant country), and prescription medications such as linaclotide, plecanatide, or lubiprostone (in severe cases)
  • Probiotics: Symptom improvement has been reported with some strains (evidence varies by product)
  • Antidepressants (SSRIs): May be useful in constipation-predominant IBS (when emotional symptoms are also present)
• Nonpharmacological treatment:
  • Psychotherapy, such as cognitive behavioral therapy (CBT) and gut-directed hypnotherapy, may help improve symptoms
• Procedures/surgery: Surgical treatment is not recommended for IBS itself (applicable only when another organic disease is identified)
• Precautions:
  • Avoid medication misuse (excessive long-term self-use of laxatives or antidiarrheals)
  • Antibiotics should be used only selectively, taking indications and adverse effects (such as resistance) into consideration
  • Use eluxadoline, rifaximin, and similar medications only after confirming the indication and safety

Checklist Before an Outpatient Visit (Including Example Questions)

• What to prepare:
  • A list of medications, nutritional supplements, and probiotics currently being taken (dose and duration of use)
  • Previous test results (copies of colonoscopy, blood tests, stool tests, and abdominal imaging results)
  • A symptom diary (for the past 2–4 weeks): Number and form of bowel movements (Bristol Stool Scale), frequency and intensity of abdominal pain (relationship to meals and stress), abdominal bloating, gas, and whether nighttime symptoms occur
  • Records of weight changes and family history (colorectal cancer, inflammatory bowel disease, etc.)
• What to show the doctor during the visit:
  • Recent weight changes and whether bloody stool, nighttime symptoms, fever, or symptoms of anemia are present
  • When the symptoms began and factors that worsen or improve them (food, stress, and medications)
• Example questions to write down before the visit:
  • “How I have recorded my diarrhea and constipation patterns over the past two weeks”
  • “Whether any of the medications I am taking are related to gastrointestinal symptoms”

General Example Questions to Ask the Doctor

• What are the main side effects of this medication (the prescribed medication)? When should I stop taking it?
• How should I start the diet recommended for my symptoms (e.g., a low-FODMAP diet)? Should I consult a dietitian?
• What is the usual prognosis after treatment? Is it possible for the symptoms to disappear completely?
• Why are tests (such as colonoscopy or an SIBO breath test) needed, and what are they intended to determine?

Examples of Condition-Specific Questions

• If my symptoms are diarrhea-predominant, is antibiotic treatment such as rifaximin likely to help? Should this be confirmed with an SIBO breath test?
• If my symptoms are constipation-predominant, should medications such as linaclotide or lubiprostone be considered? How safe are they for long-term use?

Additional guidance: If you have “warning signs” such as weight loss, bloody stool, anemia, or nighttime symptoms, you should promptly undergo additional testing and consult a specialist.