What is the recommended step‑by‑step evaluation and management of chronic abdominal pain lasting more than three months in an adult, including red‑flag assessment, appropriate investigations, and treatment options?

Chronic Abdominal Pain: Evaluation and Management

Definition and Initial Recognition

Abdominal pain is considered chronic when it has persisted for 3–6 months, and your primary task is to distinguish organic disease requiring specific treatment from functional disorders that need a fundamentally different management approach. 1

The pain may be episodic and fluctuating, related to biological, psychological, and social triggers, and can persist even after resolution of any initial peripheral insult. 1

Step 1: Red Flag Assessment

Immediately assess for alarm features that mandate urgent investigation or referral:

• Age >50 years with new-onset symptoms 2
• Unintentional weight loss >10% in 3 months or BMI <18.5 kg/m² 1
• Nocturnal symptoms that wake the patient from sleep 2
• Rectal bleeding or positive fecal occult blood 2
• Family history of gastrointestinal malignancy or inflammatory bowel disease 2
• Fever, elevated inflammatory markers (CRP, ESR), or low albumin 1, 2
• Visible abdominal distension with peristalsis (suggests mechanical obstruction) 1, 3

If any red flags are present, proceed directly to Step 3 investigations before considering functional diagnoses.

Step 2: Distinguish Mechanical Obstruction from Dysmotility

Key clinical features suggesting mechanical obstruction rather than functional pain:

• Intermittent colicky pain that worsens after eating 3
• Regular vomiting (green/yellow suggests proximal obstruction; feculent suggests distal) 1, 3
• Absolute constipation (no stool or flatus) 3
• History of multiple abdominal surgeries (adhesions cause 55–75% of small bowel obstructions) 3, 4
• Pain that improves on liquid diet or worsens with prokinetics 1

If obstruction is suspected, obtain CT abdomen/pelvis with IV contrast immediately 3, 4 —this is the gold standard and will identify transition points, ischemia, and perforation risk. 3

Common pitfall: Adhesive obstruction is frequently missed in patients with prior surgery because the bowel may be fixed and unable to dilate on imaging. 3 Obtain CT during an episode of severe pain for best diagnostic yield. 3

Step 3: Initial Laboratory and Stool Testing

Order the following baseline tests to screen for organic disease:

• Complete blood count (anemia suggests bleeding or malabsorption) 2, 4
• C-reactive protein or ESR (elevated in inflammatory bowel disease) 1, 2
• Comprehensive metabolic panel including albumin (assess nutritional status and metabolic causes) 2
• Thyroid-stimulating hormone (hypothyroidism causes dysmotility) 2
• Tissue transglutaminase IgA with total IgA (screen for celiac disease) 2, 4
• Fecal calprotectin (if <45 years with diarrhea; ≥250 µg/g strongly suggests IBD and mandates colonoscopy) 4, 5
• Fecal occult blood testing (three samples) 2
• Stool studies for ova and parasites (if diarrhea is prominent) 2

Step 4: Imaging Strategy

For chronic pain with red flags or inconclusive initial workup:

• Contrast-enhanced CT abdomen/pelvis is the gold standard 4 and changes diagnosis in 51–54% of cases. 4
• Do NOT delay CT for oral contrast—it provides no additional benefit and slows diagnosis. 4
• Plain radiographs have limited utility and should be reserved for suspected bowel obstruction only. 4

For chronic pain without red flags:

• Imaging is often unnecessary if Rome IV criteria for IBS are met (see Step 5). 1
• Avoid repeated imaging without clear clinical indication—diagnostic yield drops from 22% on initial CT to 5.9% on fourth CT. 4

Step 5: Recognize Irritable Bowel Syndrome (Rome IV Criteria)

Diagnose IBS when the following are present for ≥3 months (with symptom onset ≥6 months prior):

• Recurrent abdominal pain at least 1 day per week 1
• Associated with two or more of the following:
  • Pain related to defecation 1
  • Change in stool frequency 1
  • Change in stool form (Bristol stool scale) 1

Visible abdominal distension with bloating strongly supports IBS. 4

Once IBS is diagnosed, repetitive testing is not recommended 6 and will not improve outcomes—it reinforces illness behavior and increases healthcare costs. 6

Step 6: Consider Abdominal Wall Pain

Abdominal wall pain is frequently overlooked and mimics visceral pain:

• Can pain be elicited by physical movement or tensing abdominal muscles? 7
• Is pain localized to a circumscribed site in the abdominal wall? 7
• Does digital palpation provoke pain that increases with muscle contraction? 7

Common sites include the semilunar line (most common), linea alba, within the rectus muscle, and along the costal arch. 7 This diagnosis avoids repeated costly investigations. 7

Step 7: Exclude Opioid-Induced and Drug-Related Dysmotility

Opioid-induced bowel dysfunction and narcotic bowel syndrome are increasingly prevalent but often unrecognized:

• Chronic opioid use causes worsening abdominal pain despite escalating doses (narcotic bowel syndrome) 1
• Opioids induce hyperalgesia and worsen dysmotility 1
• Management requires opioid reduction, not escalation 1, 3
• Never add opioids for chronic functional pain—they cause dependence, gut dysmotility, and increased mortality. 2, 4

Other drugs with anticholinergic effects also worsen dysmotility. 1

Step 8: Endoscopic Evaluation

Colonoscopy with random biopsies is recommended when:

• Red flags are present 2
• Fecal calprotectin ≥250 µg/g 4
• Symptoms are severe, chronic, and refractory to initial management 2
• Age ≥50 years (colorectal cancer screening threshold) 2

Colonoscopy can diagnose microscopic colitis (a cause of chronic diarrhea and fecal incontinence in middle-aged patients) 2 and inflammatory bowel disease. 1

Step 9: Specialized Testing for Refractory Cases

If pain persists despite negative workup and fecal incontinence is present:

• Anorectal manometry and/or defecography (assess pelvic floor dysfunction and sphincter weakness) 2
• Digital rectal examination (assess for fecal impaction with overflow incontinence, sphincter tone, and masses) 2

If constipation is the predominant feature:

• Colonic transit study (Sitz marker study) 2

If severe malnutrition or dehydration is present (BMI <18.5 or >10% weight loss):

• Small bowel manometry (diagnoses neuropathy, myopathy, absent migrating motor complexes, giant contractions) 1
• Consider referral to a specialized motility center for evaluation of chronic intestinal pseudo-obstruction. 1

Step 10: Treatment Algorithm

For Functional Pain (IBS or Functional Abdominal Pain Syndrome):

• Antispasmodic agents (anticholinergics) for pain that worsens after meals 4
• Tricyclic antidepressants for frequent, refractory pain 3, 4
• Cognitive behavioral therapy and psychological support 6—essential for long-term management
• Set expectations early that pain is real, multifactorial, and not "all in their head" 1—this prevents abrupt transitions in care and maintains therapeutic alliance

For Organic Disease:

• Treat the underlying cause (e.g., IBD with anti-inflammatory therapy, celiac disease with gluten-free diet, hypothyroidism with levothyroxine) 2

For Mechanical Obstruction:

• Surgical consultation for complete obstruction or signs of ischemia 3
• Trial of non-operative management for partial obstruction (NPO, IV hydration, nasogastric decompression) 3
• Proceed to surgery if no resolution in 48–72 hours or clinical deterioration 3

Common Pitfalls to Avoid

• Do not assume functional pain in patients with prior abdominal surgery—adhesive obstruction is often missed. 3
• Do not use prokinetics in suspected obstruction—they increase perforation risk. 3
• Do not overlook narcotic bowel syndrome in chronic opioid users—requires opioid reduction, not escalation. 1, 3
• Do not perform extensive repeated imaging or endoscopy if initial workup is negative and medication-induced dysmotility is the likely cause. 2
• Elderly patients may have normal labs despite serious infection—maintain high suspicion and rely on imaging. 4

When to Refer to Gastroenterology or Surgery

Immediate referral is indicated for:

• Red flags (age >50, weight loss, nocturnal symptoms, rectal bleeding, family history of GI malignancy or IBD) 2
• Failure to respond to first-line therapies within 8–12 weeks 2
• Signs of peritonitis (rigidity, rebound tenderness) 4
• Evidence of mechanical obstruction, ischemia, or perforation on imaging 3, 4