Introduction

Chronic abdominal pain (CAP) and recurrent abdominal pain (RAP) are common complaints in paediatric practice, affecting up to 15% of school-aged children. It is often challenging to diagnose due to the wide range of possible aetiologies, from functional disorders to organic pathologies. Most often, no organic cause is found. Functional abdominal pain is a distinct disorder and does not require the exclusion of all organic causes. A systematic approach is essential to differentiate between these causes and provide effective management.

Definitions

Chronic abdominal pain (CAP)
CAP is generally defined as pain persisting for at least one to three months, occurring intermittently or continuously, and interfering with daily activities.

Recurrent abdominal pain (RAP)
RAP in children is defined as at least three episodes of pain that occur over at least three months and affect the child’s ability to perform normal activities.

Disorder of Gut-Brain Interaction (DGBI)
DGBIs affects over 40% of people and replaced ‘Functional GI Disorders’ in the 2016 publication of Rome IV criteria. DGBI highlights the complex interplay between the gut and the brain, with symptoms arising from issues in gut motility, sensitivity, immune function, microbiome composition, and central nervous system processing.

Functional abdominal pain (FAP)
FAP disorders are a group of DGBIs comprising four distinct disorders: functional dyspepsia, irritable bowel syndrome (IBS), abdominal migraine, and functional abdominal pain – not otherwise specified. (FAP-NOS)

Aetiology

The cause can stem from functional factors, organic factors, or a combination of the two, as they can occur together.

Organic Disorders
Disorder:	Key points:
Gatro-oesphageal reflux disease (GORD)	Abdominal pain (epigastric or periumbilical) aggravated by heavy meals Associated dyspeptic symptoms – waterbrash, dysphagia, regurgitation, heartburn, vomiting
Allergic enterocolitis	The term encompasses a broad range of gastrointestinal reactions to food proteins Common triggers include cow’s milk, soy, rice, and oats Food Protein-Induced Enterocolitis Syndrome (FPIES)is a non-IgE mediated food allergy FPIES typically presents with delayed onset (hours) vomiting and diarrhea after eating a trigger food Allergic proctocolitis is another type of allergic enterocolitis, specifically affects the rectum and colon, presenting with abdominal pain and rectal bleeding.
Lactose intolerance	Cramping pain, bloating, gas, or diarrhea related to eating or drinking lactose-containing products Improvement of symptoms with avoidance of lactose-containing foods
Peptic ulcer disease	Pain (epigastric or periumbilical) aggravated by meals Nocturnal abdominal pain (night wakings) Positive family history
Inflammatory bowel disease (IBD)	Abdominal pain Colitic symptoms: (in UC or Crohn’s colitis) Diarrhoea, may contain blood or mucus Abdominal cramping Tenesmus, urgency (with distal colon involvement) Pan gut involvement: (in CD; depends on site of involvement) Oral ulcers Dysphagia Dyspeptic symptoms Abdominal pain Altered bowel habits Perianal disease: fistulas, fissures, abscesses Constitutional symptoms: Fever Weight loss
Coeliac disease	Abdominal pain, predominantly associated with wheat food Bloating Constipation Altered bowel habits Poor weight gain or stunting Treatment-resistant anaemia/iron deficiency Family history of coeliac disease
Functional abdominal pain disorders
Functional abdominal pain – not otherwise specified (FAP-NOS)	Pain may be intermittent or continuous May accompany pallor and nausea (during episodes) Stress and emotional distress may act as triggers No alteration in stool pattern (frequency/consistency) Unrelated to meals or bowel motions Looks well and examines normally No obvious organic pathology can be identified
Irritable bowel syndrome (IBS)	Abdominal pain (at least 4 episodes/ month) associated with a change in stool pattern (hard to lose and watery) and defecation May be associated with straining, urgency, mucous passage, bloating and sensation of abdominal distension
Abdominal migraine	Abdominal pain (midline or diffuse) which is paroxysmal and stereotypical Episodes occur at least two times over six months Pain may last more than one hour and affects normal activities Nausea, vomiting, pallor and other vasomotor symptoms are common Well in-between attacks History of migraine in child or family member
Functional dyspepsia	Troublesome postprandial fullness Early satiety Epigastric pain not associated with alteration of stool pattern
Constipation Constipation in children is 95% due to a functional cause	Inability to fully empty the lower colon, rather than simply infrequent or hard bowel movements alone Painful or hard stools[1] , retentive posturing Straining History of fresh blood streaks on stools or on wiping Erratic stool patterns Encopresis Crampy abdominal pain, during large meals Reduction in appetite (when significant constipation) Constipation in children is 95% due to a functional cause. Therefore, it is not suitable to categorise constipation as an organic cause. Then it should be secondary to metabolic, endocrine or defecation disorder due to neuromuscular pathology, which is very rare in children.

Clinical Evaluation

A thorough history and physical examination are key to identifying red flags and guiding further investigations.

History

• Pain Characteristics: Onset, duration, location, radiation, aggravating and relieving factors, interference with daily activities
• Stool history: frequency, character (Bristol stool chart), associated blood or mucous, straining or pain on defecation, tenesmus, urgency, faecal soiling, explosive stools, toileting habits
• Associated Symptoms: Weight loss, vomiting, diarrhoea, constipation, fever, blood in stool.
• Appetite
• Drug history
• Dietary History: Food triggers (lactose intolerance, FODMAPs[1] [2] , gluten), fibre and water intake.
• Psychosocial Factors: Stress, school avoidance, anxiety, depression, family dysfunction, HEADSS assessment (older children)
• Family History: IBS, IBD, celiac disease, chronic abdominal pain (undiagnosed peptic ulcer disease), migraine, atopy and food intolerances
• Home management strategies

Physical Examination

• General examination: Growth parameters (weight, height, BMI), pubertal delay, mouth ulceration, arthritis
• Abdominal examination: tenderness, masses, faecoma, hepatosplenomegaly, distension
• Perianal examination: fissures, fistulas, skin tags
• Neurological examination if pain is atypical

Red Flags:

• Fever unexplained
• Unintentional weight loss
• Stunting
• Delayed puberty
• Nocturnal pain or diarrhoea (waking the child up from sleep)
• Chronic diarrhoea
• Gastrointestinal bleeding, blood in stools
• Persistent or bile-stained vomiting
• Dysphagia, Odynophagia
• Family history of IBD or celiac disease

Work up

Many children do not need investigations. Functional abdominal pain is a clinical diagnosis. Basis of the work up for RAP should be guided by the other differential diagnoses considered after a thorough history and examination.

Basic investigations

• Blood
  • Full blood count, CRP, ESR, LFTs, serum electrolytes, RFTs
  • In selected cases: (eg: suspected coeliac disease, IBD, pancreatitis)
    • Ferritin
    • Lipase
    • Coeliac serology
      
• Urine
  • Urine full report/dipstick
  • Pregnancy test (in menstruating females)
    
• Stool tests
  • Stool MCS 
  • In selected cases:
    • Faecal calprotectin level (for children over 4 years)
      Consider if IBD is suspected. Maybe falsely positive during episodes of infectious colitis – In Sri Lanka, this test has very low sensitivity as quantification of faecal calprotectin is unavailable.
    • H. pylori stool antigen
      If peptic ulcer disease is suspected. Results may be unreliable if on PPIs. H. pylori serology should not be performed. However, this test is not currently available in Sri Lanka.

Second-line investigations

Imaging

Imaging is not routinely required. 

• Abdominal x-ray – Not indicated for chronic non-specific pain. Should not be performed routinely to diagnose constipation.
• Ultrasound abdomen – Low yield in chronic abdominal pain. Helpful to exclude intra-abdominal masses.

MRI/ CT abdomen, contrast studies (upper GI, small bowel follow-through, barium enema), and MR enterography are rarely indicated. Has a role in identifying anatomical pathologies of the gut.

Endoscopy and biopsy 

• Consult a Paediatrician with a special interest in Gastroenterology first. 
• Useful in the diagnosis of certain structural and organic disorders – eosinophilic oesophagitis, peptic ulcer disease, coeliac disease, and inflammatory bowel disease. 
• The limitation is that it does not visualise the small bowel (except the duodenum).

Management

Functional Abdominal Pain Management

The child’s response to empiric intervention is part of the diagnostic evaluation. A diagnosis of DGBI does not mean that the child does not have pain or that it’s “all in their head.

Empiric interventions: general principles

• Establish a therapeutic alliance with the child and family
• Provide reassurance that serious pathology is rare
• Educate the family: acknowledge the pain is real, but there is no physical damage to treat
• Encourage a return to normal activities (including school attendance, having fun).
• Maintain a prospective symptom diary
• Treat constipation
• Provide follow-up

Approach	Interventions
Behavioural approached (Psychosocial Support)	Caregiver-led To encourage validation, reassurance, positive attention, and feedback, acknowledge the pain, and reinforce “health” by identifying emotional and psychological stressors of the child. Identify emotional and psychological stressors of the child. Therapist-led Cognitive-behavioural therapy (CBT) for stress-related symptoms – Not an established service in Sri Lanka yet. Suggest coping skills and relaxation techniques (paediatric counsellor) Assist in identifying triggers (dietary, anxiety, sleep, medications)
Dietary Modifications	Avoid excessive dairy if lactose intolerance is suspected Increase fibre intake for constipation Reduce high-fat, spicy, or gas-producing foods (low FODMAP diet)
Chronic Constipation	The goal of management is the complete evacuation of the lower colon Normality can take up to 2 – 6 months to restore Consider if stool disimpaction therapy is required prior to commencing maintenance therapy Osmotic Laxatives (mainstay management; used long-term): Polyethylene glycol (Movicol), Lactulose Stimulant laxatives (bisacodyl and senna) should be reserved for short-term use Topical Petroleum Jelly for anal fissures Severe constipation may require manual disimpaction, enemas or suppositories (note these measures may only evacuate stools primarily in the rectum and routine use should be avoided) Dietary modifications Reduce excess dairy consumption Fluid intake to meet the maintenance requirement Encourage high fibre intake (may aggravate symptoms if used before stool softening, therefore suggest commencing later when passing soft stools) Good toileting habits Parental education, daily calendar, rewards for attempting defecation and rewards for absence of encopresis Encourage physical activity Refractory constipation requires further evaluation.
Pharmacological Therapy (only in selected Cases)	Probiotics for gut dysbiosis Antispasmodics (e.g., hyoscine) for IBS-related pain Antacids, proton pump inhibitors or H2 receptor blockers for dyspeptic symptoms Loperamide or rifaximin for diarrhoea-predominant IBS Tricyclic antidepressants (low-dose) to relieve anxiety, but should be left as a last resort after utilising the above strategies.

Organic Abdominal Pain Management

Treatment is condition-specific and should include longitudinal follow-up to assess the response to treatment and if re-evaluation or referral to a paediatric gastroenterologist is required.

• GERD: Acid suppression therapy, lifestyle modifications.
• FPIES: Exclusion diet – cow’s milk, soy, oats. Resolution of symptoms with exclusion clinically confirms the diagnosis. (strategic step-ladder re-introduction of foods can be utilised with time)
• Peptic ulcer disease: Triple therapy for h.pylori infection (to patient and family members), empiric antisecretory therapy, avoidance of NSAIDs.
• Celiac Disease: Lifelong gluten-free diet.
• IBD: Immunosuppressive/Immunomodulatory therapy, nutritional support. Suggest paediatric gastroenterologist follow-up.

Refer to paediatric ESPGHAN guidelines for specific information on management of each condition.

Important considerations

• Most children with functional abdominal pain improve over time with reassurance and appropriate management, and the overall outcome is good.
• Identifying and addressing psychological stressors significantly improves outcomes.
• A supportive and understanding environment at home and school is important.
• Referral to a Paediatrician with a special interest in gastroenterology is warranted in cases with persistent red flag signs or treatment failure.

References

• Lake AM. Chronic abdominal pain in childhood: diagnosis and management. American Family Physician. 1999 Apr 1;59(7):1823-30.
• Portal MR. Abdominal pain-chronic.
• Balakrishnan K, Chiou EH, Li BU. Patient education: Chronic abdominal pain in children and adolescents (Beyond the Basics).
• Gray L. Chronic abdominal pain in children. Australian family physician. 2008 Jun 1;37(6):398.
• Reust CE, Williams A. Recurrent abdominal pain in children. American family physician. 2018 Jun 15;97(12):785-93.
• https://theromefoundation.org/rome-iv/rome-iv-criteria/

Abbreviations

• CAP     – Chronic abdominal pain
• RAP     – Recurrent abdominal pain
• DGBI    – Disorders of gut-brain interaction
• FAP-NOS- Functional abdominal pain – Not otherwise specified
• IBS       – irritable bowel syndrome
• GORD  – gastro-oesophageal reflux disease
• IBD      – inflammatory bowel disease
• UC       – ulcerative colitis
• CD       – Crohn’s disease
• CRP      – C-reactive protein
• ESR      – erythrocyte sedimentation rate
• FPIES   – Food Protein-Induced Enterocolitis Syndrome
• LFT       – liver function test
• RFT      – renal function test
• MRI     – magnetic resonance imaging
• CT        – computed tomography
• CBT      – cognitive behavioural therapy
• FODMAP – fermentable oligosaccharides, disaccharides, monosaccharides, and polyols

Prepared by:
Dr Aanjeli Wimalasiri
Lecturer in Paediatrics
University of Peradeniya

Reviewed by:
Dr Wathsala Hathagoda
Senior Lecturer in Paediatrics
University of Colombo