Abdominal Pain in Children Algorithm

Safety

Red Flags — Exclude surgical emergencies and serious diagnoses first

Done

Abdominal pain is extremely common in children — over 90% is benign. But surgical emergencies must not be missed.

Peritonism Guarding, rebound tenderness, rigid board-like abdomen, absent bowel sounds → 999 — perforation / peritonitis

Bilious vomiting + pain Bowel obstruction, volvulus, intussusception → 999

Severe RIF pain + fever Evolving appendicitis → Same-day surgical — Paediatric Surgery Assessment

Intussusception features Age 6–18mo, colicky pain, pallor, drawing-up legs, "redcurrant jelly" stools → 999

Testicular pain + abdominal pain Testicular torsion — surgical emergency up to 6hrs → 999 — always examine genitalia in boys with abdominal pain

Trauma + abdominal pain Solid organ injury, non-accidental injury — seat-belt sign, bruising pattern → 999 + safeguarding

DKA presentation Vomiting + abdominal pain + polyuria + known / suspected T1DM → 999

Sudden-onset severe pain Vascular event, torsion, perforation, pneumonia-referred pain → 999

Bloody diarrhoea + pain VTEC / intussusception / inflammatory bowel disease → Same-day ED

Fever + RIF + anorexia in girl Also consider ovarian torsion / pelvic inflammatory disease in post-pubertal girls → Same-day surgical / gynaecology

Appendicitis is the most common surgical emergency in children, with peak incidence at 10–12 years but can occur at any age. Perforation rates are 20–40% in children (higher than adults) because children present later and diagnosis is more challenging due to atypical presentations. Every 6-hour delay in diagnosis doubles perforation risk.

Testicular torsion is time-critical — viability is 90–100% if detorsion within 6 hours, dropping to 50% at 12 hours, and <10% at 24 hours. Boys with abdominal pain MUST have the scrotum examined. Torsion can present as lower abdominal pain with minimal testicular symptoms.

Non-accidental injury (NAI) should be considered in any child with unexplained abdominal injury, particularly with bruising on the abdominal wall, back, or buttocks. The "seat-belt" bruise pattern across the abdomen in a child not in a road traffic accident is a NAI red flag.

Diagnose

Characterise the pain — SOCRATES adapted for children

Done

History is limited in young children — observe behaviour, parent report, and use age-appropriate pain tools (FLACC scale <5yr, FACES 3–7yr, NRS ≥8yr).

Site / radiation

Periumbilical → RIF migration = classic appendicitis. RIF alone = appendicitis, mesenteric adenitis, Crohn's. Generalised = constipation, functional, gastroenteritis. Epigastric = GORD, gastritis, pancreatitis. Loin to groin = renal colic (rare in children).

Onset

Sudden severe = torsion, perforation, volvulus. Gradual worsening over hours = appendicitis, UTI. Colicky (comes and goes) = constipation, intestinal obstruction, intussusception, biliary, renal. Chronic persistent = functional, IBD, coeliac.

Character

Colicky = visceral origin (bowel/ureter). Sharp / constant = peritoneal irritation. Burning epigastric = GORD / gastritis. Dull central + bloating = constipation / functional abdominal pain.

Associated symptoms

Anorexia (appendicitis — almost universal). Vomiting (surgical, GE, obstruction). Diarrhoea (GE, IBD, constipation overflow). Dysuria / frequency (UTI). Weight loss (IBD, coeliac, malignancy).

Duration

<24hrs + worsening = urgent surgical assessment. 24–72hrs = appendicitis in evolution if localising to RIF. Chronic (>4 weeks recurrent) = functional abdominal pain, IBD, coeliac, constipation.

Relieving / exacerbating

Better after defaecation = constipation / functional. Worse with movement = peritonism. Food-related = GORD, gastroparesis. School-related = functional, anxiety. Worse with periods = dysmenorrhoea / endometriosis (adolescent girls).

The classic periumbilical → RIF migration of appendicitis pain occurs in only 50–60% of children — atypical presentations are common and include generalised pain, diarrhoea, and vomiting. The Paediatric Appendicitis Score (PAS) combines clinical and laboratory features and has a sensitivity of 90% for appendicitis — it can be used as a screening tool in primary care to guide urgency of referral.

Anorexia is present in >90% of appendicitis cases and is one of the most useful discriminating features — a hungry child with abdominal pain is much less likely to have appendicitis than an anorexic one. Always ask "Has your child been eating normally?" and "Did they want their usual favourite food today?"

Diagnose

Age-based differential diagnosis — most likely diagnoses by age group

Done

0–3 months

Infantile colic (diagnosis of exclusion). Constipation. Intussusception (age 3mo+). Testicular torsion in boys. Incarcerated hernia. NAI. Always rule out organic causes before diagnosing colic.

3–12 months

Intussusception (peak 6–18mo). Hernia. Colic if <3–4mo. Gastroenteritis. UTI. Constipation.

1–5 years

Constipation (most common at all ages), mesenteric adenitis (viral), UTI, gastroenteritis, intussusception (up to 5yr), appendicitis (less common <5yr but severe), trauma. Henoch-Schönlein Purpura (HSP): purpura + joint pain + abdominal pain.

5–12 years

Appendicitis (peak 10–12yr), functional abdominal pain / FAP (most common cause of recurrent pain), constipation, mesenteric adenitis, IBD (Crohn's/UC), coeliac, gastritis, UTI, renal colic. In girls: ovarian cyst, mittelschmerz, gynaecological.

Functional abdominal pain

Rome IV criteria: ≥4 episodes/month for ≥2 months. No organic explanation found. Associated with anxiety, school stress, family conflict. Accounts for ~10% of all paediatric presentations. Not a diagnosis of exclusion — it IS a diagnosis.

Mesenteric adenitis

Viral illness + RIF pain + lymphadenopathy on USS. Self-limiting. Managed with analgesia and reassurance. Can mimic appendicitis — USS helps distinguish but does not always.

Functional abdominal pain (FAP) / centrally mediated abdominal pain syndrome (CAPS) is the most common cause of recurrent abdominal pain in school-age children, accounting for 90% of chronic recurrent pain presentations. It is not a diagnosis of exclusion after exhaustive negative investigations — making a positive diagnosis with confidence and communicating it well to families prevents unnecessary tests and builds therapeutic alliance.

HSP (Henoch-Schönlein Purpura / IgA vasculitis) must not be missed — it presents as colicky abdominal pain (in 60%), arthritis (in 80%), and purpuric rash on buttocks and legs (100%). Renal involvement (haematuria, proteinuria) in 40% requires monitoring. Any child with purpuric rash + abdominal pain = HSP until proven otherwise.

Diagnose

Targeted Examination — systematic approach

Done

General impression

Lying very still (peritonism) vs. writhing / rolling (colic). Pallor = significant pathology. Jaundice = hepatobiliary. Dehydration signs. Ill-looking = urgent. Smiling, playing with phone = reassuring for functional.

Abdomen — observation

Distension (obstruction, organomegaly, constipation). Scars (previous surgery — adhesions). Visible peristalsis (pyloric stenosis in infant). Bruising (NAI, trauma).

Abdomen — palpation

Start away from the pain. McBurney's point (2/3 from umbilicus to ASIS) = appendicitis. Rovsing's sign (LIF pressure → RIF pain) = peritoneal irritation. Rebound / guarding = peritonism. Hepatomegaly, splenomegaly. Faecal mass (constipation).

Genitalia (boys)

Examine scrotum in EVERY boy with abdominal pain — torsion can present as abdominal pain without obvious testicular symptoms. High-riding, horizontal testicle + pain = torsion → 999.

Genitalia (girls)

Consider pelvic pathology in post-pubertal girls. Adnexal tenderness, PID. Consider pregnancy test in adolescent girls — ectopic pregnancy is a surgical emergency.

Hernial orifices

Groin, umbilicus, scars — examine for incarcerated hernia. Tender irreducible hernia = strangulation → 999.

Perianal / rectal

Inspect for fissures (constipation). Do NOT perform PR in primary care. Blood on nappy / underwear → further assessment.

Skin / joints

Purpuric rash (HSP), jaundice, pallor, clubbing (IBD), arthritis. Examine joints if HSP suspected.

The examination of the scrotum in boys with abdominal pain is life-altering if torsion is present. Studies show that testicular torsion is missed in primary care in up to 20% of cases because the genitalia are not examined. A child with 6 hours of severe abdominal pain presenting at 2am who "just has a tummy ache" may have testicular torsion. Check every time.

Children with peritonism lie very still because movement exacerbates pain. Driving over a speed bump or bumpy car journey increases pain (Dunphy's sign). A child who arrives in the waiting room running around is unlikely to have peritonitis. Observe the child's behaviour before and during the consultation.

Diagnose

Investigations — targeted by diagnosis

Done

Urine dipstick / MSU

Mandatory first step All children with abdominal pain. UTI mimics appendicitis (especially in girls). Leucocytes alone can be present in appendicitis (proximal ureteral irritation) — send MSU to confirm.

Blood glucose + urine ketones

Any child with vomiting + pain — exclude DKA. BM strip in surgery takes 30 seconds. Urine dipstick for glucose and ketones.

Pregnancy test (urine hCG)

All post-menarchal girls with lower abdominal pain. Ectopic pregnancy is life-threatening and must be excluded. Urine hCG >25 = pregnant until proven otherwise.

FBC + CRP + WBC

Paediatric Appendicitis Score includes WBC. CRP >50 + WBC >15 + localising signs = high appendicitis risk. However: normal bloods do NOT rule out early appendicitis. Do not be falsely reassured.

Stool calprotectin

For chronic / recurrent pain Raised in IBD (sensitivity 90%). >200mcg/g → refer paeds gastro. Normal <50mcg/g → IBD unlikely. Useful first-line test before invasive investigation.

Coeliac serology (tTG IgA + total IgA)

Recurrent abdominal pain + any of: faltering growth, iron deficiency anaemia, fatigue, diarrhoea, family history. Sensitivity 95%.

AXR

Not for diagnosis of constipation (NICE). Useful if suspected bowel obstruction (erect film — air-fluid levels, absent bowel gas). Hospital-initiated.

USS abdomen

Hospital-initiated. Appendicitis (sensitivity 85%, limited by obesity / bowel gas). Intussusception (target sign). Ovarian pathology. Not available in primary care but key investigation in ED.

Faecal calprotectin is a major advance in distinguishing IBD from functional abdominal pain. It is a neutrophil protein released during gut mucosal inflammation — raised in Crohn's and UC, normal in functional pain. A systematic review (2019) found sensitivity 93% and specificity 94% for IBD at a threshold of 50mcg/g. Requesting this test avoids many unnecessary colonoscopy referrals while appropriately identifying IBD.

Normal blood results (FBC, CRP) do NOT rule out early appendicitis — 30% of proven appendicitis cases present with normal CRP and WBC in the first 12 hours. This is a high-stakes clinical decision. If you have a clinical gestalt that "something is wrong," refer even with normal bloods.

Refer

Referral Criteria

Done

999

Peritonism (guarding, rebound, rigid abdomen). Bilious vomiting + pain. Suspected torsion (testicular or ovarian). Suspected intussusception. Severe haematemesis. DKA. Ectopic pregnancy. Shock.

Same-day surgical

Suspected appendicitis (RIF pain + anorexia + fever). Age <5yr with significant abdominal pain (higher perforation risk, harder to assess). Incarcerated hernia. Bloody diarrhoea + severe pain.

Same-day paeds/ED

Unable to exclude surgical diagnosis. Significant dehydration. Pain uncontrolled. HSP with severe abdominal or renal involvement. Age <3 months with pain (organic cause more likely). DKA screen positive.

Paeds outpatient (urgent)

Raised stool calprotectin (suspected IBD). Positive coeliac serology. Recurrent unexplained pain >1 month not responding to simple measures. Weight loss + pain. Jaundice + pain.

Primary care manage

Functional abdominal pain — after appropriate assessment. Constipation-related pain. Mild gastroenteritis — well child. Mesenteric adenitis — diagnosis of exclusion after surgical cause excluded.

Safeguarding

Unexplained bruising over abdomen / back / buttocks. Inconsistent history. Multiple attendances with abdominal pain. Affect not matching reported pain severity. Refer to MASH / named GP.

Children under 5 with appendicitis have higher perforation rates (50–80%) compared to older children because: they cannot localise pain well, parents and clinicians attribute pain to constipation or GE, and the omentum is poorly developed so cannot contain perforation. Any child under 5 with significant unexplained abdominal pain should have a low threshold for same-day surgical assessment.

IBD (Crohn's disease) in children can present insidiously over months with abdominal pain, fatigue, and weight loss without obvious bowel symptoms. Perianal disease (fistulae, skin tags) is present in 20% and is pathognomonic of Crohn's. Examine the perianal region and refer early — early treatment prevents bowel damage and growth failure.

Treat

Treatment — condition-specific management

Done

Functional abdominal pain

Explanation + CBT / pain management NICE first-line

Positive diagnosis. Validate pain as real. Explain brain-gut connection. CBT, hypnotherapy, mindfulness. Low-FODMAP diet trial (dietitian referral). Avoid excessive medical investigation.

Constipation-related pain

Macrogol + toilet training

Movicol Paediatric Plain (see constipation algorithm). Pain resolves with bowel function normalised. Distinguish from appendicitis — constipation pain responds quickly to disimpaction.

GORD / gastritis

Omeprazole 0.7–1.4mg/kg OD

4-week trial. If no response → re-evaluate diagnosis. H. pylori: breath test (UBT) if suspected; treat if positive with triple therapy (under specialist guidance).

Analgesia — acute pain

Paracetamol 15mg/kg PO/PR 4–6hrly + ibuprofen 5–10mg/kg 8hrly if age ≥3mo. Do NOT withhold analgesia pending surgical assessment — it does not mask signs and improves examination quality. Evidence-based.

Mesenteric adenitis

Self-limiting — analgesia, fluids, reassurance. Duration 1–2 weeks. Follow-up if not improving to exclude missed appendicitis. Antibiotics not indicated (viral aetiology).

HSP management

Analgesia (NSAIDs initially, paracetamol if renal involvement). Urine monitoring weekly x 4 weeks (haematuria / proteinuria). Steroids in specialist setting only for severe abdominal or renal involvement.

UTI with abdominal pain

See fever algorithm — treat with trimethoprim or nitrofurantoin (see Step 7 fever algorithm). Pain and vomiting resolve rapidly once UTI treated.

The evidence strongly supports giving analgesia before surgical assessment — three RCTs and a Cochrane review (2011) showed analgesia does NOT mask signs of appendicitis and significantly reduces patient distress without changing surgical outcomes. Withholding analgesia in a child with abdominal pain is now considered poor practice.

For functional abdominal pain, gut-directed hypnotherapy and CBT are more effective than medication in reducing pain episodes and school absenteeism. A systematic review (2017) found CBT reduced pain frequency by 50% vs 25% in controls. Antispasmodics (mebeverine, hyoscine) have weak evidence in children. Avoid unnecessary PPI prescribing — gut microbiome effects.

Lifestyle

Supportive measures — especially for functional abdominal pain

Done

Normalise and validate Explain that functional pain is real, common, and not dangerous. Avoid catastrophising language ("nothing wrong"). Say instead: "Your gut is very sensitive — it's a real signal from a very sensitive nervous system." This reduces anxiety and pain amplification.

Maintain normal activities School attendance is critical — every day off school reinforces pain avoidance behaviour. Write to school with management plan. GP fit note is NOT appropriate for functional abdominal pain — it prolongs illness.

Low-FODMAP diet Fermentable carbohydrates trigger IBS-type symptoms. Trial of 4–6 weeks under dietitian guidance can reduce functional pain by 50–60%. Not appropriate without dietitian support — nutritional risk in growing children.

Stress and anxiety management School bullying, academic pressure, family conflict are common triggers. Address with parents and school. Refer CAMHS if anxiety is significant. Mindfulness apps (Headspace for Kids, Calm) are useful adjuncts for children ≥8yr.

Regular eating pattern Skipping meals triggers pain in many children. Regular breakfast, lunch, and dinner. Avoid high-fat, high-spice, and carbonated drinks if symptomatic. Adequate fibre (fruits, vegetables, wholegrains).

Adequate hydration 6–8 cups fluid/day. Dehydration causes GI dysmotility and pain sensitisation. Water preferred. Limit fizzy drinks (carbonation causes bloating and pain).

School absenteeism is the most important functional outcome in paediatric chronic abdominal pain. Children who miss school develop educational deficits, social isolation, anxiety, and depression — all of which amplify pain. An early, clear message that school attendance is expected and supported reduces long-term morbidity more than any medication.

The gut-brain axis explains functional abdominal pain mechanistically — visceral hypersensitivity, altered gut motility, and central sensitisation all contribute. Explaining this brain-gut connection using age-appropriate language (e.g., "your stomach has its own little brain that gets stressed when you're worried") has been shown to reduce parent catastrophising and improve treatment compliance.

Safety

Follow-up, Safety-Netting & Monitoring

Done

Acute pain — first episode

Review within 24–48hrs if: suspected appendicitis not meeting 999 threshold, amber features, diagnostic uncertainty. Earlier if deteriorating.

Functional pain

Review 4–6 weeks — has the intervention (diet, CBT, school support) helped? Pain diary useful. Growth parameters at each visit. Red flags review.

IBD / coeliac follow-up

Once referred and diagnosed: GP role includes monitoring growth, nutrition, medication side effects (e.g., azathioprine monitoring: FBC, LFTs 3-monthly). Annual influenza and pneumococcal vaccination (immunosuppressed).

HSP monitoring

Urine dipstick (blood + protein) weekly for 4 weeks, then monthly for 6 months. BP measurement monthly. Refer paeds nephrology if proteinuria >1+ persists or haematuria + proteinuria together.

Call 999 if:

Pain suddenly much worse. Vomit turns green. Child becomes floppy / pale. Abdomen becomes hard / rigid. Severe difficulty breathing (pneumonia-referred abdominal pain).

Same-day if:

Pain persists >6hrs and worsening. Fever developing or worsening. Anorexia persisting. Repeated visits with same pain. New mass palpable. Urinary symptoms develop. Parent overriding your reassurance.

Documentation key points

Record exact location of maximal tenderness, guarding, rebound, bowel sounds, genitalia exam (boys). Signed and timed. If referring for suspected appendicitis — document clinical features that prompted referral clearly.

Time-based safety-netting is critical for abdominal pain — "come back if it gets worse" is insufficient. Specify: "If the pain is still there in 6 hours and getting worse, go straight to A&E — do not wait for a GP appointment." This specificity correlates with better decision-making by parents and earlier presentation for surgical assessment.

HSP nephritis develops weeks after the initial presentation and is the most serious complication — 5% of children develop chronic kidney disease. Monthly urine and BP monitoring for 6 months is essential and is a primary care responsibility. The NICE guideline for HSP (2017) is explicit that GPs should lead follow-up monitoring.