What is the appropriate workup and treatment for a 17-year-old with symptoms suggestive of Irritable Bowel Syndrome (IBS)?

IBS Workup in a 17-Year-Old

A 17-year-old with typical IBS symptoms (abdominal pain related to bowel habit changes, no alarm features) requires only limited baseline investigations—full blood count, inflammatory markers (CRP or ESR), and coeliac serology—before making a positive diagnosis and initiating treatment. 1

Initial Clinical Assessment

Cardinal Symptoms to Confirm

• Abdominal pain (upper or lower abdomen) that is temporally related to altered bowel habit—either relieved/exacerbated by defecation or occurring when constipation worsens or diarrhea increases 1
• Altered stool frequency and/or consistency using Bristol stool chart to classify predominant pattern (IBS-D, IBS-C, or mixed) 1
• Bloating (highly suggestive when present, though not required for diagnosis) 1

Alarm Features That Would Change the Workup

• Unintentional weight loss ≥5% 2
• Rectal bleeding or blood in stool 1, 3
• Nocturnal symptoms that wake the patient 1
• Family history of inflammatory bowel disease or colon cancer 1, 2
• Fever or anemia 2
• If any alarm features are present, proceed to colonoscopy 1

Additional History Elements

• Onset timing (postinfection, after antibiotics, following acute stress) 1
• Extraintestinal symptoms (back pain, urological, gynecological symptoms) 1
• Medication use, particularly opioids 1
• Psychological comorbidities and stressors 1

Required Baseline Investigations

At age 17 with typical symptoms and no alarm features, the following tests are sufficient: 1

• Full blood count (to exclude anemia) 1
• C-reactive protein or ESR (to exclude inflammation) 1
• Coeliac serology (antiendomysial or tissue transglutaminase antibodies) 1, 3

Additional Testing Based on Symptom Pattern

If diarrhea-predominant (IBS-D):

• Faecal calprotectin (to exclude inflammatory bowel disease in patients <45 years with diarrhea) 1
  • If ≥250 μg/g: proceed to colonoscopy 1
  • If 100-249 μg/g: repeat off NSAIDs/PPIs; refer for colonoscopy if remains elevated 1
• Consider stool microscopy for ova and parasites if relevant travel history 1

If severe watery diarrhea, nocturnal diarrhea, or prior cholecystectomy:

• Consider bile acid diarrhea testing (SeHCAT scan or serum 7α-hydroxy-4-cholesten-3-one) 1

Investigations NOT Indicated

• Colonoscopy is NOT indicated in a 17-year-old without alarm features or family history of colon cancer 1, 2
• Hydrogen breath testing for small intestinal bacterial overgrowth or carbohydrate intolerance is NOT recommended 1
• Exocrine pancreatic insufficiency testing is NOT indicated 1

Making the Positive Diagnosis

Once alarm features are excluded and baseline tests are normal, make a firm positive diagnosis of IBS based on symptom criteria alone—do not pursue further investigations. 1

The diagnosis is highly likely when:

• Female sex 1
• Symptom duration >2 years 1
• History of frequent consultations for non-GI symptoms 1
• Normal physical examination including rectal examination 1

Initial Management After Diagnosis

Patient Education (Critical First Step)

Explain IBS as a disorder of gut-brain interaction with a benign but relapsing-remitting course—emphasize that cure is unlikely but substantial symptom improvement is achievable. 1, 2

• Address fears directly (particularly cancer concerns) rather than ordering more tests 1, 2
• Explain how stress, diet, and brain-gut interactions affect symptoms 1, 2

First-Line Treatment for All Patients

1. Regular physical exercise (foundation of treatment with benefits lasting up to 5 years) 1, 2

2. Dietary modifications: 2

• Balanced diet with adequate fiber intake
• Regular meal times and time for defecation
• Proper sleep hygiene

3. Soluble fiber (psyllium/ispaghula): 2

• Start 3-4 g/day, build up gradually to avoid bloating
• Avoid insoluble fiber (wheat bran) which worsens symptoms 2

Symptom-Specific Pharmacological Treatment

For abdominal pain/cramping:

• Antispasmodics (dicyclomine or mebeverine) as first-line for meal-related pain 2
• Side effects: dry mouth, visual disturbance, dizziness 2

For diarrhea-predominant (IBS-D):

• Loperamide 2-4 mg up to four times daily (regularly or prophylactically) 2
• Titrate carefully as abdominal pain, bloating, and constipation may limit tolerability 2

For constipation-predominant (IBS-C):

• Increase dietary fiber to 25 g/day or use psyllium 2
• Polyethylene glycol (osmotic laxative) if fiber insufficient 2

Probiotics:

• Trial for 12 weeks for global symptoms and abdominal pain 2
• Discontinue if no improvement after 12 weeks 2

Follow-Up and Escalation

Review treatment efficacy after 3 months. 2

If symptoms persist after 3 months of first-line treatment:

• Tricyclic antidepressants (amitriptyline 10 mg at bedtime, titrate to 30-50 mg) as gut-brain neuromodulators 2
• Explain these are NOT for depression but for pain modulation 2

If symptoms persist after 12 months of pharmacological treatment:

• Refer for IBS-specific cognitive behavioral therapy or gut-directed hypnotherapy 2
• Consider earlier referral if symptoms relate to stressors or anxiety/depression is present 2

Critical Pitfalls to Avoid

• Do not pursue colonoscopy in patients <45 years without alarm features 2
• Do not use opioids for chronic abdominal pain management 2
• Do not order extensive testing once diagnosis is established—this reinforces illness behavior and increases anxiety 1, 2
• Do not dismiss symptoms as "just psychological"—IBS has clear pathophysiological mechanisms 3