Acute Abdominal Pain In Children

Acute abdominal pain is among the commonest presentations in paediatric emergency care, accounting for 5 to 10% of visits. Young children cannot localise or describe pain, the differential varies markedly with age, and serious surgical conditions can present subtly. Most children (50 to 60%) have a non-specific or self-limiting diagnosis (gastroenteritis, constipation, viral illness, mesenteric adenitis, functional pain); 5 to 10% need surgery, with appendicitis the commonest.

Differential diagnosis by age:

Neonates and infants (under 1 year).

• Infantile colic (after excluding red flags)
• Gastroenteritis and gastro oesophageal reflux
• Intussusception (peak 3 to 12 months)
• Malrotation with midgut volvulus (most within the first month, but at any age)
• Incarcerated inguinal hernia
• Necrotising enterocolitis (preterm infants)
• Hirschsprung disease with enterocolitis
• Pyloric stenosis (vomiting without pain in the first weeks)
• Testicular torsion, urinary tract infection
• Non-accidental injury

Toddlers and preschool children (1 to 5 years).

• Gastroenteritis, constipation, urinary tract infection, intussusception, appendicitis (perforation rate up to 70 to 90% under 3 years), Meckel diverticulum, viral illness, lower lobe pneumonia, foreign body ingestion (button batteries, magnets, coins), lead poisoning, incarcerated hernia

School age (6 to 12 years).

• Appendicitis, mesenteric adenitis, constipation, functional abdominal pain, gastroenteritis, urinary tract infection or pyelonephritis, urolithiasis, IgA vasculitis (Henoch-Schonlein purpura), diabetic ketoacidosis, streptococcal pharyngitis, sickle cell crisis, inflammatory bowel disease, coeliac disease, peptic ulcer, abdominal migraine

Adolescents.

• Appendicitis, ovarian torsion, ruptured ovarian cyst, ectopic pregnancy, pelvic inflammatory disease, dysmenorrhoea and endometriosis, testicular torsion, inflammatory bowel disease, gallstones and cholecystitis (haemolytic disease, obesity), pancreatitis, renal colic, constipation, eating disorder complications

• History from the parent and, where possible, the child:
  • onset and character (sudden severe pain suggests torsion or perforation; intermittent severe pain with drawing up of the legs and pallor every 15 to 20 minutes suggests intussusception)
  • vomiting (bilious vomiting is a surgical emergency until proven otherwise; projectile non-bilious vomiting suggests pyloric stenosis)
  • stool (redcurrant jelly stool in intussusception; bloody diarrhoea in infective colitis, haemolytic uraemic syndrome or inflammatory bowel disease)
  • fever, urinary symptoms, menstrual history, trauma, medication, ingestion, travel, sick contacts
• Examination:
  • haemodynamics (heart rate, capillary refill, hydration, blood pressure) and general appearance (a child who lies still, refuses to move or cries when the bed is bumped may have peritonitis)
  • Watch the child walk, hop or cough, which reproduces pain in peritonitis.
  • Palpate starting away from the pain with distraction; look for guarding, rebound and a sausage shaped mass (intussusception).
  • Always examine the hernial orifices, testes, throat, chest, back and perineum.
  • Rectal examination only when it will change management.
• Red flags: bilious or faeculent vomiting, rigid or distended abdomen, rectal bleeding, peritonism, severe unrelenting pain, persistent right iliac fossa tenderness, haemodynamic instability, a toxic looking child, dehydration or sepsis. Appendicitis in young children may present with fever, vomiting and irritability with diffuse tenderness.

• Initial tests: urinalysis with culture, glucose and ketones (DKA), full blood count, C-reactive protein, electrolytes, urea and creatinine, lipase, liver function, blood gas and lactate in the unwell, beta-hCG in post-menarchal females, and group and save if surgery is likely
• Ultrasound is the first line imaging for most paediatric abdominal pain. It identifies:
  • appendicitis (non-compressible blind ending tube over 6 mm)
  • intussusception (target or doughnut sign, sensitivity 98 to 100%)
  • pyloric stenosis (muscle thickness over 3 mm, channel length over 15 mm)
  • ovarian torsion (enlarged ovary with reduced or absent flow; normal Doppler does not exclude torsion)
  • testicular torsion, hydronephrosis and gallbladder disease
• Abdominal radiograph: limited use; shows free air, obstruction (double bubble in duodenal atresia, dilated loops), constipation and radio opaque foreign bodies
• Upper gastrointestinal contrast study for suspected malrotation or volvulus (corkscrew duodenum, duodenojejunal junction to the right of the midline)
• CT, using a low dose protocol, for equivocal cases, trauma or complications; rapid MRI where available for appendicitis to avoid radiation
• Clinical scores (Paediatric Appendicitis Score, Alvarado, risk calculators) are used alongside imaging

Resuscitation and general care. Treat dehydration and shock with isotonic crystalloid 10 to 20 mL/kg boluses, repeated as needed, then maintenance fluids. Keep nil by mouth if surgery is possible.

Do not withhold analgesia:

• paracetamol 15 mg/kg (maximum 1 g) orally or IV every 4 to 6 hours
• ibuprofen 10 mg/kg (maximum 400 mg) every 6 to 8 hours if there is no renal or bleeding concern
• IV morphine 0.05 to 0.1 mg/kg titrated
• intranasal or IV fentanyl 1 microgram/kg for severe pain

Ondansetron 0.1 to 0.15 mg/kg (maximum 4 mg) for vomiting. Early surgical review for red flags.

Intussusception. Resuscitate, give IV fluids and exclude perforation. Non-operative reduction by air or hydrostatic enema under ultrasound or fluoroscopic guidance (air pressure up to 80 to 120 mmHg; success 80 to 95%) with a surgeon present in case of perforation. Laparoscopic or open reduction, with resection of non-viable bowel, for failed reduction, peritonitis or perforation. Look for a pathological lead point (Meckel diverticulum, polyp, lymphoma, cystic fibrosis) in older children and in recurrence.

Malrotation with volvulus. Emergency: nasogastric decompression, fluid resuscitation, antibiotics (for example cefotaxime 50 mg/kg with metronidazole), and immediate surgery with the Ladd procedure (detorsion, division of Ladd bands, widening of the mesenteric base, appendicectomy, bowel placed in non-rotation). Delay risks loss of the whole midgut.

Appendicitis. Resuscitation, analgesia, ceftriaxone 50 mg/kg (maximum 2 g) with metronidazole 10 mg/kg (maximum 500 mg), and laparoscopic appendicectomy within 12 to 24 hours for uncomplicated disease. Perforated disease needs 3 to 5 days of IV antibiotics after surgery, until afebrile for 24 hours, with a normal white count and tolerating diet.

Torsion. Testicular torsion: surgical exploration within 6 hours (salvage above 90% in the first 6 hours, under 10% after 24 hours), manual detorsion as a temporising measure, and bilateral orchidopexy. Ovarian torsion: laparoscopic detorsion with ovarian conservation, even if the ovary looks dusky.

Other conditions.

• Urinary tract infection: ceftriaxone 50 to 75 mg/kg IV daily or oral cefalexin 25 mg/kg per dose two to three times daily, or co-amoxiclav, guided by culture, for 7 to 10 days (3 to 5 days for simple lower tract infection)
• Gastroenteritis: oral rehydration solution (50 mL/kg over 4 hours for mild to moderate dehydration), ondansetron, no routine antibiotics
• Constipation: polyethylene glycol 3350 1 to 1.5 g/kg/day for disimpaction, then 0.4 to 0.8 g/kg/day, with dietary measures
• DKA: fluids and insulin 0.05 to 0.1 units/kg/hour
• IgA vasculitis: supportive care with monitoring of urine and blood pressure
• Streptococcal pharyngitis: penicillin V 250 mg (under 27 kg) or 500 mg (above 27 kg) two to three times daily for 10 days
• Mesenteric adenitis: supportive, a diagnosis of exclusion
• Functional abdominal pain: reassurance and cognitive behavioural strategies

Disposition. Admit for observation with serial examinations if a serious cause cannot be excluded. Discharge only if pain is controlled, the child is drinking and afebrile or stable, with clear advice to return for bilious vomiting, bloody stool, worsening or localising pain, fever, persistent vomiting or drowsiness.