What is the best approach to diagnose and treat chronic stomach pain in an adult with no prior history of gastrointestinal issues?

Chronic Stomach Pain: Diagnostic and Treatment Approach

For an adult with chronic stomach pain and no prior gastrointestinal history, begin with a focused evaluation to exclude organic disease using limited testing (complete blood count, inflammatory markers, celiac serology), then establish a functional diagnosis and initiate neuromodulator therapy with low-dose tricyclic antidepressants while avoiding opioids entirely. 1

Initial Diagnostic Strategy

History and Physical Examination Focus

• Duration and pattern: Confirm pain has persisted 3-6 months, assess if episodic or constant, and determine relationship to meals (postprandial pain 30-90 minutes after eating suggests biliary or peptic disease) 1
• Red flag symptoms: Specifically ask about unintentional weight loss, dysphagia, hematemesis, melena, or pain radiating to the back (which suggests pancreatitis or aortic pathology rather than functional disease) 1
• Risk factors for chronic pain: Screen for history of prior chronic pain conditions, early-life trauma or adversity, catastrophizing behaviors, pre-existing anxiety/depression, and negative social support 1, 2
• Carnett's sign: Have the patient tense abdominal muscles by lifting head/shoulders while you palpate the painful area—if pain worsens, this indicates abdominal wall pain rather than visceral pain 3

Limited Laboratory and Imaging Workup

• Initial labs only: Complete blood count, comprehensive metabolic panel, inflammatory markers (ESR/CRP), and celiac serology (tissue transglutaminase IgA) 1, 4
• Imaging is NOT routinely indicated unless red flags are present: CT abdomen/pelvis is appropriate only if alarm features exist (weight loss, anemia, elevated inflammatory markers) 1
• Upper endoscopy is indicated only if: age >60 years, alarm symptoms present, or symptoms of peptic ulcer disease with risk factors for H. pylori 1
• Stop repetitive testing once functional diagnosis is established—continuing investigations increases costs without benefit and reinforces illness behavior 1, 2, 4

Establishing the Diagnosis

Functional vs. Organic Disease

Once basic workup is negative, establish a functional diagnosis rather than continuing exhaustive testing. 1, 4 The most common functional disorders causing chronic abdominal pain are:

• Functional dyspepsia: Epigastric pain or burning, postprandial fullness, early satiety 5
• Irritable bowel syndrome (IBS): Abdominal pain associated with altered bowel habits (constipation, diarrhea, or mixed pattern) 1, 5
• Centrally mediated abdominal pain syndrome (CAPS): Constant or nearly constant abdominal pain unrelated to physiological events, often with other somatic symptoms 1, 6

Critical Communication Framework

Tell the patient explicitly that: (1) their pain is real, (2) pain is processed and modulated in the brain, (3) peripheral factors can drive increased pain, and (4) pain is modifiable. 1

• Explain that chronic pain involves central amplification mechanisms where the brain continues to scan for threats from the gut based on prior experiences, mistakenly engaging unhelpful higher-order processes 1
• Use the Fear-Avoidance model to explain why some people have more pain than others despite similar diagnoses, which instills hope that changing one's approach to pain can improve function 1
• Avoid language suggesting the patient "shouldn't be in so much pain" or continuing to order tests to find the "cause"—this engages in pain catastrophizing 1, 2

Treatment Algorithm

First-Line Pharmacologic Management

Start low-dose tricyclic antidepressants (TCAs) as first-line neuromodulator therapy:

• Amitriptyline 10 mg once daily at bedtime, titrating slowly every 1-2 weeks to a maximum of 30-50 mg daily for pain management 2, 6
• TCAs modulate pain processing in the brain and spinal cord with analgesic properties independent of mood effects—lower doses often suffice for pain relief 2
• Adverse effects (dry mouth, constipation, sedation) occur within days, but analgesic efficacy takes 1-3 weeks 2
• TCAs are superior to SSRIs for abdominal pain based on meta-analysis data 2

Alternative neuromodulator if TCAs not tolerated:

• Duloxetine (SNRI) 30 mg daily, increasing to 60 mg daily after 1 week, provides pain relief through descending pain modulation pathways 6

Symptom-Specific Adjunctive Therapy

For predominant dyspepsia/epigastric pain:

• Proton pump inhibitor (omeprazole 20 mg once daily) for 4-8 weeks if symptoms suggest acid-related disease 7
• If H. pylori testing is positive: Triple therapy with omeprazole 20 mg twice daily + clarithromycin 500 mg twice daily + amoxicillin 1 g twice daily for 10-14 days 7

For IBS with constipation:

• Increase dietary fiber to 25 g/day, though evidence for pain reduction is mixed 1

For IBS with diarrhea:

• Loperamide 2-4 mg up to four times daily to reduce loose stools, urgency, and fecal soiling 1

Non-Pharmacologic Interventions (Initiate Early)

Brain-gut psychotherapies should be introduced at the outset of care, not as a last resort: 1

• Cognitive behavioral therapy (CBT): 4-12 sessions focusing on cognitive reframing, exposure, relaxation training, and flexible problem-solving—most effective for patients with insight into how thoughts, feelings, and behaviors relate to pain 1
• Gut-directed hypnotherapy: Effective for patients with visceral hypersensitivity and somatic symptoms, delivered by certified clinical providers (avoid if severe PTSD present) 1
• Breathing techniques and relaxation training: Can be taught by the gastroenterologist immediately to address heightened autonomic arousal 2

Dietary modifications:

• Consider referral to specialized gastroenterology dietitian for low FODMAP diet if dietary triggers suspected—supervised by trained dietitian for moderate-to-severe symptoms 2
• Mediterranean diet may help patients with psychological-predominant symptoms 2

Critical Medication Avoidance

NEVER prescribe opioids for chronic functional abdominal pain:

• Opioids cause narcotic bowel syndrome (occurs in ~6% of chronic users), characterized by paradoxic worsening pain despite escalating doses 1, 8
• Opioids are ineffective for functional pain, cause dependence, gut dysmotility, serious infection risk, and increased mortality 2, 8, 5
• If patient is already on opioids when referred, prescribe responsibly via multidisciplinary collaboration until they can be discontinued 1

When to Refer to Specialists

Refer to psychologist/psychiatrist if:

• Limited or no response to baseline neuromodulators and self-management strategies 1, 2
• Moderate-to-severe depression symptoms, suicidal ideation, or significant psychiatric comorbidities present 1, 2
• History of trauma, abuse, or poor coping styles (catastrophizing) that interfere with adjustment to illness 1

Refer to gastroenterologist if:

• Alarm features develop (weight loss, anemia, dysphagia, hematemesis) 1
• Symptoms refractory to first-line treatments after 3-6 weeks 1
• Consideration of advanced therapies or multidisciplinary pain management program needed 1, 5

Common Pitfalls to Avoid

• Do not continue imaging or endoscopy once functional diagnosis is established—this reinforces illness behavior and increases costs without benefit 1, 2, 4
• Do not dismiss pain as "psychological" in a pejorative sense—validate that both gastrointestinal and psychological symptoms are real and require treatment 1, 2
• Do not wait 12 months to offer psychological therapies—introduce early as part of comprehensive management 6
• Do not use antispasmodics as monotherapy for chronic pain—they may help meal-related cramping but do not address central pain mechanisms 1
• Recognize tramadol as an opioid with addiction potential and opioid-associated adverse events—avoid for chronic functional pain 1