Functional Abdominal Pain

Definition

Episodic or continuous abdominal pain occurring at least 4 times per month for a minimum of 2 months.
Absence of identifiable inflammatory, anatomic, metabolic, or neoplastic processes explaining symptoms.
Classified under disorders of gut-brain interaction (DGBI) via Rome IV criteria.
Pain severity mimics organic disease; distress is genuine.

Driven by biopsychosocial model integrating genetics, environment, and psychosocial factors.
Visceral hyperalgesia: Altered, excessive perception of normal gut motility interpreted as pain.
Brain-gut axis dysfunction: Abnormal bidirectional communication between enteric nervous system and central nervous system.
Sensitization triggered by prior gastrointestinal infections, inflammation, cow milk allergy, or psychological trauma.
Gut microbiota alterations and immune mucosal dysfunction influence pain thresholds.

Subtype	Core Clinical Criteria
Functional abdominal pain - not otherwise specified	Episodic/continuous periumbilical pain; insufficient criteria for other functional disorders.
Irritable bowel syndrome	Pain associated with defecation, change in stool frequency, or change in stool form/appearance.
Functional dyspepsia	Postprandial fullness, early satiety, or epigastric pain/burning unrelated to defecation.
Abdominal migraine	Paroxysmal, intense periumbilical/midline pain lasting >1 hour; associated with anorexia, nausea, vomiting, headache, photophobia, pallor.

Absence of alarm signs permits symptom-based diagnosis without extensive invasive testing. Presence dictates targeted investigation.

Category	Alarm Features
Systemic/Growth	Involuntary weight loss, linear growth deceleration, delayed puberty, unexplained fever.
Gastrointestinal	Gastrointestinal blood loss (hematochezia, occult), severe chronic or nocturnal diarrhea, dysphagia, persistent vomiting.
Pain Characteristics	Pain awakening child from sleep, persistent right upper or right lower quadrant pain, radiation to back/shoulder.
Physical/Family History	Perianal fistulae/tags, arthritis, hepatosplenomegaly, family history of inflammatory bowel disease or celiac disease.

Restrict testing if typical functional features exist lacking red flags.
Screening panel: Complete blood count, erythrocyte sedimentation rate, C-reactive protein, comprehensive metabolic panel.
Celiac screening: Tissue transglutaminase IgA, total serum IgA.
Stool assays: Fecal calprotectin (differentiates functional pain from inflammatory bowel disease), occult blood, ova/parasites.
Avoid routine abdominal ultrasonography or endoscopy unless indicated by specific alarm symptoms.

Validate symptoms; explain brain-gut axis and visceral hyperalgesia concepts using simple analogies.
Provide reassurance regarding benign, non-progressive disease nature.
Normalize lifestyle; mandate return to school; minimize secondary gain and excessive parental attention to pain behaviors.
Utilize cognitive behavioral therapy, gut-directed hypnotherapy, mindfulness, and relaxation techniques to improve coping skills.

Maintain well-balanced, age-appropriate nutrition with adequate fiber.
Limit carbonated beverages, excessive fruit juices (fructose/sorbitol), and refined foods to reduce bloating.
Trial low-FODMAP (fermentable oligo-, di-, monosaccharides, and polyols) diet for pain associated with severe bloating.

Agent Class	Specific Therapies And Indications
Antispasmodics	Peppermint oil, hyoscyamine; target smooth muscle spasms in irritable bowel syndrome.
Probiotics	Lactobacillus rhamnosus GG; moderately increases treatment success, restores altered gut flora.
Neuromodulators	Amitriptyline (tricyclic antidepressant) or citalopram (SSRI); reserved for refractory, disabling pain with comorbid anxiety/depression.
Cyproheptadine	Enhances gastric accommodation in functional dyspepsia; useful for early satiety and nausea.