What is a do not miss diagnosis for stress-induced flatulence in a patient already on anxiety medication, such as selective serotonin reuptake inhibitors (SSRIs)?

Do-Not-Miss Diagnosis: Microscopic Colitis

The critical do-not-miss diagnosis in a patient with stress-induced flatulence already on SSRIs is microscopic colitis, particularly given that SSRIs themselves are a known precipitating drug for this condition. 1

Why Microscopic Colitis Must Be Excluded

Microscopic colitis presents with chronic watery diarrhea and gastrointestinal symptoms that can easily be misattributed to functional disorders or medication side effects. The British Society of Gastroenterology specifically identifies SSRIs as potential precipitating drugs for microscopic colitis, alongside NSAIDs, PPIs, and statins. 1

High-Risk Features That Should Trigger Evaluation

You must consider colonoscopy with biopsies when the patient exhibits:

• Female sex 1
• Age ≥50 years 1
• Coexistent autoimmune disease 1
• Nocturnal or severe, watery diarrhea 1
• Duration of diarrhea <12 months 1
• Weight loss 1
• Current SSRI use (as in this case) 1

Critical Diagnostic Approach

Colonoscopy with colonic biopsies is the only way to diagnose microscopic colitis, as the mucosa appears normal on endoscopic examination. 1 The diagnosis requires histological confirmation showing increased intraepithelial lymphocytes and subepithelial collagen deposition (collagenous colitis) or increased intraepithelial and lamina propria lymphocytes (lymphocytic colitis). 1

Common Pitfall to Avoid

Do not assume gastrointestinal symptoms in a patient on SSRIs are purely functional or stress-related without excluding microscopic colitis, especially if any of the above risk factors are present. The yield of colonoscopy is extremely low in typical IBS patients, but substantially higher when atypical features or risk factors for microscopic colitis exist. 1

Secondary Considerations

Inflammatory Bowel Disease (IBD)

While less likely to present primarily as flatulence, IBD must be considered if:

• Alarm symptoms are present: rectal bleeding, unintentional weight loss, nocturnal symptoms, family history of gastrointestinal cancer or IBD 1
• Severe or progressive symptoms despite treatment 1
• New-onset symptoms in the context of known psychological comorbidity (as anxiety and depression affect up to 40% of IBD patients) 1, 2

Bile Acid Diarrhea (BAD)

Primary or idiopathic bile acid diarrhea should be considered in patients with suspected IBS-D who have atypical features. 1 This can coexist with stress-related symptoms and may require specific testing (SeHCAT scan where available, or empiric trial of bile acid sequestrants). 1

Small Intestinal Bacterial Overgrowth (SIBO)

Breath testing should be performed to exclude carbohydrate intolerance and SIBO, particularly if bloating and flatulence are prominent symptoms. 3

Why This Matters for Morbidity and Quality of Life

Microscopic colitis, if left undiagnosed, leads to chronic diarrhea, malnutrition, and severely impaired quality of life. 1 Unlike functional disorders, it has specific treatments (budesonide, bile acid sequestrants) that can induce remission. 1 Missing this diagnosis condemns the patient to ongoing symptoms that could be effectively treated.

The psychological burden of undiagnosed organic disease is substantial, and patients with IBD or microscopic colitis who are misdiagnosed with functional disorders experience worse outcomes, increased healthcare utilization, and deteriorating mental health. 1, 2