What is the best course of treatment for a patient with diffuse abdominal pain, nausea, and diarrhea for 6 weeks, with abdominal tenderness and worsening lower abdominal pain on palpation?

Diagnostic Workup and Treatment Approach

This patient requires urgent diagnostic evaluation to exclude organic pathology before considering functional disorders, given the 6-week duration, worsening pain, and significant abdominal tenderness on examination.

Initial Diagnostic Evaluation

The presence of diffuse abdominal pain with tenderness and worsening lower abdominal pain on palpation for 6 weeks warrants immediate investigation to exclude serious organic disease before attributing symptoms to a functional disorder 1.

Essential First-Line Investigations

Perform these baseline tests immediately:

• Complete blood count to assess for anemia, infection, or inflammatory markers 1
• Inflammatory markers (C-reactive protein or erythrocyte sedimentation rate) to identify inflammatory processes 1
• Serum chemistries and albumin to evaluate for metabolic derangements or malabsorption 1
• Stool studies including:
  • Fecal occult blood testing 1
  • Ova and parasites examination 1
  • Fecal calprotectin if diarrhea is prominent 1
• Celiac serology given the chronic diarrhea 1

Imaging Studies

Given the physical examination findings of tenderness and worsening lower abdominal pain with palpation, imaging is essential:

• CT scan of abdomen and pelvis with oral and intravenous contrast is the most appropriate initial imaging study for diffuse abdominal pain with lower abdominal tenderness 1, 2
• This will exclude bowel obstruction, inflammatory conditions (diverticulitis, inflammatory bowel disease), abscess formation, and other structural pathology 1

Common pitfall: Do not assume this is irritable bowel syndrome (IBS) without excluding organic disease first. The presence of significant abdominal tenderness on examination is an alarm feature that mandates investigation 1.

Endoscopic Evaluation

Colonoscopy is indicated in this patient because:

• Chronic diarrhea lasting 6 weeks with abdominal tenderness suggests possible inflammatory bowel disease or microscopic colitis 1
• The worsening nature of symptoms and physical examination findings constitute alarm features 1
• Colonoscopy with biopsies can diagnose inflammatory bowel disease, microscopic colitis, or other mucosal pathology 1

Additional considerations for colonoscopy:

• If patient is over age 50, colonoscopy is strongly recommended regardless of other factors 1
• Younger patients with diarrhea, weight loss, or other alarm features should undergo colonoscopy 1

Treatment Approach Based on Findings

If Organic Disease is Identified

Treat the specific condition accordingly (e.g., inflammatory bowel disease with appropriate immunosuppression, diverticulitis with antibiotics if indicated, etc.) 1.

If Initial Workup is Negative

Only after excluding organic pathology, consider functional disorders:

For Diarrhea-Predominant Symptoms:

First-line treatments:

• Loperamide for diarrhea control, titrating dose carefully to avoid constipation 1
• Dietary modifications including trial of soluble fiber (ispaghula 3-4 g/day, gradually increased) 1
• Consider bile acid malabsorption testing (serum 7α-hydroxy-4-cholesten-3-one) if diarrhea persists, especially if there is history of cholecystectomy 1

Second-line treatments if first-line fails:

• Tricyclic antidepressants (amitriptyline 10 mg once daily, titrated to 30-50 mg) for abdominal pain and global symptoms 1
• These work as gut-brain neuromodulators and are effective for pain management 1

For Abdominal Pain:

If pain is the predominant symptom:

• Antispasmodic medications can be tried, though side effects (dry mouth, visual disturbance, dizziness) are common 1
• Tricyclic antidepressants are more effective for chronic pain and should be considered early 1

Critical Monitoring

Re-evaluate the patient in 3-6 weeks:

• If symptoms worsen or new alarm features develop, repeat imaging and consider further endoscopic evaluation 1
• Persistent symptoms despite treatment warrant referral to gastroenterology for specialized management 1

Red flags requiring immediate re-evaluation:

• Development of fever, severe pain, or signs of peritonitis 1, 2
• Inability to tolerate oral intake or progressive symptoms 1
• New onset rectal bleeding or significant weight loss 1

Key Pitfalls to Avoid

1. Do not diagnose IBS without excluding organic disease in a patient with 6 weeks of symptoms and significant abdominal tenderness 1
2. Do not rely solely on physical examination - imaging and laboratory studies are essential given the duration and examination findings 2, 3
3. Do not delay colonoscopy if the patient has alarm features or is over age 50 1
4. Serial examinations are crucial if initial workup is equivocal, as some conditions (like bowel ischemia) may take time to declare themselves 1