What is the role of gastroscopy and colonoscopy in diagnosing irritable bowel syndrome (IBS)?

Role of Gastroscopy and Colonoscopy in IBS

Gastroscopy and colonoscopy are generally not indicated for diagnosing IBS in typical cases, but colonoscopy becomes necessary when specific risk factors for microscopic colitis are present or when alarm features suggest alternative diagnoses. 1

Gastroscopy in IBS

There is no routine role for gastroscopy (upper endoscopy) in the diagnosis or management of IBS. 1

• Upper endoscopy should only be performed if patients report upper gastrointestinal symptoms such as dysphagia, persistent vomiting, or epigastric pain that suggests alternative diagnoses like peptic ulcer disease or celiac disease requiring biopsy confirmation 1
• The British Society of Gastroenterology explicitly states there is no indication for routine gastroscopy in adult IBS patients without upper GI symptoms 1

Colonoscopy in IBS: General Principles

The yield of colonoscopy in patients with typical IBS symptoms is extremely low, and there is no evidence that patients derive reassurance from a normal examination. 1

• Colonoscopy should not be performed routinely in patients under age 50 with typical IBS symptoms and no alarm features 1
• The diagnosis of IBS should be made positively based on symptom criteria (Rome IV or similar), not as a diagnosis of exclusion requiring endoscopy 1
• Exhaustive investigation to exclude all organic pathology is unnecessary and may be counterproductive, potentially reinforcing illness behavior 2, 3

When Colonoscopy IS Indicated in IBS

Alarm Features Requiring Colonoscopy

Any patient with alarm symptoms must undergo colonoscopy regardless of meeting IBS criteria: 1, 4

• Rectal bleeding (not attributable to hemorrhoids or anal fissure) 4, 5
• Unintended weight loss 5
• Anemia or iron deficiency 4, 5
• Fever 1
• Abnormal physical examination findings (abdominal, rectal, or anal mass) 1
• Family history of colorectal cancer or inflammatory bowel disease 4
• Age ≥50 years at symptom onset 1

Specific Indication: Microscopic Colitis Screening

Colonoscopy with biopsies should be considered in IBS-D patients with specific risk factors for microscopic colitis, as this is the only way to diagnose this condition: 1

Risk factors warranting colonoscopy to exclude microscopic colitis include: 1

• Female sex
• Age ≥50 years
• Coexistent autoimmune disease
• Nocturnal diarrhea or severe, watery diarrhea
• Duration of diarrhea <12 months
• Weight loss
• Use of precipitating medications (NSAIDs, PPIs, SSRIs, statins)

The prevalence of microscopic colitis in IBS-D cohorts is approximately 1.5%, with all cases identified in the diarrhea-predominant subtype 1. Approximately 10% of individuals with chronic watery diarrhea may have microscopic colitis 1. Colorectal biopsy remains the gold standard and only definitive method for diagnosing microscopic colitis. 1

Alternative to Full Colonoscopy

• Flexible sigmoidoscopy can be considered as an alternative to full colonoscopy for diagnosing microscopic colitis, as the condition typically affects the entire colon 1

Critical Diagnostic Algorithm

Before considering any endoscopy, the following baseline tests should be completed: 4, 2, 3

1. Complete blood count (to detect anemia) 4
2. C-reactive protein or ESR (to assess for inflammation) 4
3. Celiac serology (IgA-tTG) - mandatory in all suspected IBS patients regardless of stool pattern 4, 2, 3
4. Fecal calprotectin (in patients <45 years with diarrhea to exclude IBD) 1, 4, 2

If fecal calprotectin is >250 µg/g, colonoscopy is indicated to exclude inflammatory bowel disease. 1

Common Pitfalls to Avoid

• Never diagnose IBS without first testing celiac serology, as celiac disease is the most commonly missed organic diagnosis in IBS-like presentations 4
• Do not perform colonoscopy for "reassurance" in typical IBS patients without risk factors, as evidence shows this does not provide meaningful reassurance and wastes resources 1
• Do not assume normal inflammatory markers (CRP, ESR) exclude all organic disease - they do not rule out microscopic colitis or celiac disease 4
• Avoid premature closure on IBS diagnosis in patients over 50 without colonoscopy, especially with diarrhea-predominant symptoms, as microscopic colitis risk increases with age 1
• Do not order colonoscopy in patients taking NSAIDs within the past 6 weeks without first stopping the medication, as NSAIDs can cause colitis mimicking IBS 1

Quality of Life Considerations

• IBS adversely affects health-related quality of life to a degree exceeding most other medical disorders, including impairment of physical, psychosocial, emotional, and role function 1
• However, unnecessary endoscopic procedures do not improve quality of life and may reinforce illness behavior 1
• The focus should be on positive diagnosis using symptom criteria and targeted investigation only when specific risk factors are present 1, 3