Functional Abdominal Pain Disorders in Children

See also paeds inflammatory bowel disease and coeliac disease (paediatric) for organic differentials.

Functional abdominal pain disorders (FAPDs) are a heterogeneous group — chronic abdominal pain not fully explained by another medical condition, now considered a subset of disorders of gut–brain interaction (DGBI). Affect ~13.5% of children worldwide. Pathophysiology is multifactorial: altered gut motility, visceral hypersensitivity, and the microbiota–gut–brain axis; tends to cluster in families.

Rome IV subtypes

Subtype	Diagnostic criteria (>4 episodes/month, >2 months, unless noted)
Functional dyspepsia	Postprandial fullness, early satiation, or epigastric pain/burning unrelated to defecation
Irritable bowel syndrome	Abdominal pain plus pain associated with defecation (not resolved by treating constipation) and/or a change in stool frequency/appearance
Abdominal migraine	Paroxysmal pain ≥1 hour, recurring over weeks–months, significantly impairing function, a predictable pattern per patient, with ≥2 of: anorexia, nausea, vomiting, headache, photophobia, pallor (over ≥6 months)
Functional abdominal pain — NOS	Intermittent/persistent pain not tied to eating or menstruation, not meeting criteria for the above

Clinical assessment

A symptom diary helps. Ask about autoimmune disease and family history of IBD, coeliac disease and migraine; take a gynaecological history in girls (symptom overlap). Assess psychosocial stressors, school participation and family dynamics — parental response to symptoms significantly affects outcome. ~50% of children with FAPD have coexisting anxiety/depression — screen proactively, since functional impairment tracks with psychological symptom severity, and untreated psychological distress increases the likelihood of symptoms persisting into adulthood.

Examination: growth (serial measurements), pubertal staging, hydration, abdominal exam. PR exam only if specifically indicated (e.g. rectal bleeding, significant anorectal pain) and with consent.

Red flags (→ consider organic disease)

Growth faltering or delayed puberty; persistent/frequent or bile-/ blood-stained vomiting; dysphagia/odynophagia; persistent diarrhoea (especially worse at night); GI bleeding, unexplained iron deficiency/ anaemia; localised/persistent pain (especially RLQ/RUQ); perianal disease; unexplained fever; arthritis; family history of IBD, coeliac disease or peptic ulcer disease.

Investigations

A thorough clinical assessment is usually enough to exclude organic causes — invasive/extensive investigation is not routinely needed and can itself perpetuate anxiety.

• Routine: urinalysis, stool MC+S ± ova/cysts/parasites; ± FBC/UEC/LFT; ± CRP.
• Targeted, only if indicated: H. pylori testing, coeliac serology, faecal calprotectin (note significant day-to-day variation, and seek specialist advice if testing under age 4), serum lipase, iron studies, STI screen/pregnancy test, abdominal ultrasound (low yield for chronic pain itself, but useful to exclude a mass if exam is abnormal), endoscopy ± biopsy.
• AXR is not routinely performed for non-specific abdominal pain.
• FAPDs can coexist with organic disease (e.g. IBD, lactose intolerance) and with each other — don’t assume finding one explanation rules out everything else.

Management

A biopsychosocial approach — strong therapeutic relationship, confirming a positive diagnosis (not just “nothing’s wrong”), and validating symptoms are the foundation.

• Patient/family education and reassurance are the mainstay — explain visceral hypersensitivity/“false alarm” pain signals, and that attention itself can amplify pain. Set realistic goals (e.g. return to school/ sport) rather than aiming for complete pain eradication.
• Review diet regularly — restrictive trigger-food avoidance can cause nutritional deficiency and poor growth; involve a dietitian as needed. Address sleep, exercise and eating habits.
• Probiotics: a Cochrane review found only low-quality evidence of benefit — not yet recommended as standard practice.
• CBT has the best evidence base, improving both pain and psychological outcomes (including cost-effective internet-delivered programs).
• Gut-directed hypnotherapy shows long-lasting improvement in pain, anxiety, depression and quality of life, though predictors of response are limited.
• Treat coexisting anxiety/depression — associated with greater functional impairment and poorer recovery.
• Refer to paediatric gastroenterology if the diagnosis is uncertain, or to help address perpetuating behavioural factors.