Key Facts

Intussusception occurs when a proximal segment of bowel (the intussusceptum) telescopes into the adjacent distal segment (the intussuscipiens). It is the most common abdominal emergency in early childhood and requires prompt diagnosis and management to prevent bowel ischaemia and necrosis.

Epidemiology

Incidence is approximately 1-4 per 1,000 children. Peak age is 6-9 months. Male:female ratio approximately 3:2. Seasonal variation with peaks in spring and autumn, correlating with viral illness. Accounts for approximately 1-4% of all paediatric abdominal emergencies.

Aetiology

Idiopathic (~95% in typical age group): Likely triggered by lymphoid hyperplasia (Peyer's patches) in the terminal ileum following viral infection (adenovirus, rotavirus, respiratory viruses).

Pathological lead point (~5% in <2 years; ~60% in >2 years):

• Meckel's diverticulum
• Intestinal polyp (Peutz-Jeghers)
• Lymphoma (Burkitt's)
• Duplication cyst
• Henoch-Schönlein purpura (intramural haematoma)

Pathophysiology

The intussusceptum is propelled distally by peristalsis, dragging its mesentery with it → mesenteric venous compression → bowel wall oedema → mucosal ischaemia → mucus and blood secretion (redcurrant jelly stool) → if untreated: arterial compromise → bowel necrosis → perforation → peritonitis. Lymphatic and venous obstruction precede arterial compromise.

Classic Presentation

• Paroxysmal colicky abdominal pain: Infant draws knees up, screams, pallor during episodes; pain-free intervals (child may appear well between episodes initially)
• Vomiting: Initially non-bilious, becoming bilious as obstruction progresses
• Bloody stool ('redcurrant jelly'): Mucus mixed with blood — late sign indicating mucosal ischaemia
• Palpable abdominal mass: Sausage-shaped in the right upper quadrant/transverse colon; relative emptiness in the right iliac fossa (Dance's sign)

Atypical Presentations

• Lethargy and pallor without obvious pain (especially in young infants — can mimic sepsis)
• Diarrhoea (may be misdiagnosed as gastroenteritis)
• Altered consciousness

Red Flags

• Bilious vomiting with colicky pain — bowel obstruction
• Abdominal distension with peritonism — bowel necrosis/perforation
• Profound lethargy/shock in infant — intussusception must be considered
• Bloody stool in an infant with abdominal pain — urgent assessment

Bedside

• Abdominal examination: Sausage-shaped mass (RUQ), Dance's sign (empty RIF), abdominal distension
• Rectal examination: Blood/mucus on finger (redcurrant jelly)
• Observations: Tachycardia, fever (if bowel necrosis), signs of shock

Bloods

• FBC: Leucocytosis (inflammation/infection)
• U&Es: Dehydration, electrolyte imbalance
• Blood gas: Metabolic acidosis if compromised bowel
• Group and save/crossmatch: In case surgical intervention needed

Imaging

• Abdominal ultrasound: Investigation of choice
  • Target/doughnut sign (transverse view): Concentric rings of bowel within bowel
  • Pseudokidney sign (longitudinal view): Layered appearance
  • Sensitivity >95%, specificity ~100%
  • Can also assess blood flow (Doppler) and trapped fluid
• Abdominal X-ray: May show soft tissue mass, absence of gas in RIF, small bowel obstruction; normal AXR does not exclude intussusception

Special Tests

• Not routinely required; CT rarely needed in children (may identify lead point in older children)

Non-pharmacological

• Nil by mouth: Once diagnosis confirmed
• IV access and fluid resuscitation: Correct dehydration before intervention
• Nasogastric tube: If vomiting/distension

Pharmacological

• IV fluids: 0.9% NaCl for resuscitation and maintenance
• Analgesia: Paracetamol 15mg/kg QDS, morphine 0.1mg/kg IV for severe pain
• Antibiotics: IV co-amoxiclav 30mg/kg TDS or ceftriaxone + metronidazole if peritonitis suspected

Surgical/Interventional

• Air enema reduction: First-line treatment; performed under fluoroscopy or US guidance
  • Success rate: 80-95% for ileocolic intussusception
  • Contraindications: Peritonitis, perforation, prolonged symptoms (>48h) with signs of bowel compromise
  • Perforation risk: ~0.5-2.5%
  • Three attempts are typically permitted before proceeding to surgery (rule of three: 3 attempts, max pressure 120 mmHg, 3 minutes each)
• Surgical reduction: Required if enema fails, peritonitis, or perforation
  • Manual reduction via right lower quadrant incision or laparoscopy
  • Resection and primary anastomosis if bowel is gangrenous
  • Lead point excision if identified
• Observation post-reduction: Monitor for recurrence (5-10%), especially in first 72 hours

Referral Criteria

• All suspected intussusception — emergency paediatric surgical referral
• Immediate surgery consultation if signs of peritonitis or perforation

• Air/hydrostatic enema reduction: Success rate 80-95%; excellent outcomes
• Recurrence: Approximately 5-10% after non-operative reduction; lower after surgical reduction (~1-2%)
• Mortality: <1% with prompt treatment in developed countries; historically >50% if untreated
• Bowel necrosis: Risk increases with duration of symptoms >24-48 hours
• Lead point lesions: Prognosis depends on underlying pathology (benign polyp vs lymphoma)
• Post-reduction: Most children recover rapidly and can be discharged within 24-48 hours

USS Findings in Intussusception

Lead Points by Age