Intussusception - Paediatric

Quick Answer

Intussusception is the telescoping of one bowel segment into another, most commonly ileocolic (90%), presenting classically with intermittent colicky abdominal pain, "red currant jelly" stool, and a palpable mass. Peak incidence at 6-18 months (70% below 2 years). Diagnosis confirmed by ultrasound showing "target sign" or "pseudokidney sign". First-line treatment is air or contrast enema reduction (85-95% success if below 24h symptoms), with surgery reserved for failed reduction or perforation. Lethargy and altered mental status occur in 20-30% and may precede other symptoms—consider intussusception in any lethargic infant.

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ACEM Exam Focus

What Examiners Expect

Primary Written: Pathophysiology of bowel obstruction, mesenteric ischemia, fluid and electrolyte disturbances in paediatric bowel obstruction.

Primary Viva:

• Anatomy of ileocolic junction and lymphoid tissue (Peyer's patches)
• Pathophysiology of venous congestion → arterial compromise → bowel necrosis
• Mechanism of encephalopathy (? endotoxin, ? cytokine release)

Fellowship Written: Recognition of atypical presentations, investigation algorithm, indications for non-operative vs surgical management, differential diagnosis of paediatric abdominal pain with bleeding.

Fellowship OSCE: Paediatric abdominal examination, communication with anxious parents, procedural consent for enema reduction, recognition and resuscitation of shocked infant with bowel obstruction.

Key Exam Traps

1. Lethargy as presenting feature: Not just pain—lethargy occurs in 20-30% and may be the first sign
2. "Red currant jelly" stool is late: Present in only 50-60% on initial presentation
3. Classic triad present in below 50%: Do not exclude intussusception based on incomplete triad
4. Recurrence risk: 10-15% after enema reduction, 2-5% after surgical reduction
5. Pathological lead point: Consider in below 6 months, greater than 3 years, or recurrent intussusception (5-10% have Meckel's, polyp, lymphoma)

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Key Points

1. Epidemiology: Peak 6-18 months (70% below 2 years); incidence 1-4 per 1,000 live births; male:female ratio 3:2
2. Ileocolic intussusception accounts for 90%, ileocecal and ileoileal for 10%
3. Classic triad (colicky pain, red currant jelly stool, palpable mass) present in only 15-40% at initial presentation
4. Ultrasound is diagnostic: "target sign" (doughnut) on transverse view, "pseudokidney sign" on longitudinal view (sensitivity 98-100%, specificity 88-100%)
5. Air enema reduction is first-line (success 85-95% if below 24h, 60-70% if greater than 24h); contraindicated in peritonitis or perforation
6. Recurrence occurs in 10-15% after enema, 2-5% after surgery; most within 24-72 hours
7. Lethargy/encephalopathy in 20-30%—may precede abdominal signs; mechanism unclear (? endotoxin, ? cytokine release, ? hyponatraemia)

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Clinical Overview

Definition

Intussusception is the invagination (telescoping) of a proximal segment of bowel (intussusceptum) into the lumen of an adjacent distal segment (intussuscipiens), leading to bowel obstruction, venous congestion, oedema, and potential ischaemia or perforation.

Classification

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Epidemiology

Incidence & Demographics

• Incidence: 1-4 per 1,000 live births (Western populations); up to 6 per 1,000 in some Asian populations
• Peak age: 6-18 months (70% occur in children below 2 years; 90% below 3 years)
• Gender: Male predominance (M:F ratio 3:2)
• Seasonal variation: Increased incidence in late autumn/winter (corresponding to viral illness peaks)

Age-Specific Considerations

Key Evidence: Kaiser et al. (2007) retrospective review of 1,092 intussusception cases: 82% below 2 years, 7% below 3 months (pathological lead point in 23%), 3% greater than 5 years (lead point 47%).

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Pathophysiology

Mechanism

1. Initiation: A lead point (lymphoid hyperplasia, Meckel's diverticulum, polyp) or dysmotility causes telescoping of proximal bowel into distal lumen
2. Venous congestion: Mesenteric veins compressed → venous oedema and engorgement of intussuscepted segment
3. Arterial compromise: Progressive oedema → arterial compression → ischaemia of bowel wall
4. Mucosal damage: Ischaemia → mucosal sloughing → bloody stool ("red currant jelly")
5. Perforation: If untreated greater than 24-48 hours → full-thickness necrosis → perforation and peritonitis

Lead Points

Idiopathic (90-95% in infants):

• Enlarged Peyer's patches (lymphoid hyperplasia post-viral infection)
• Adenovirus, rotavirus, enterovirus implicated

Pathological lead points (5-10% overall, up to 30% greater than 5 years):

Key Evidence: Bines et al. (2006): Rotavirus vaccination (original tetravalent RotaShield) associated with 1 in 10,000 increased risk of intussusception in first 7 days post-vaccination. Current vaccines (RotaTeq, Rotarix) have much lower risk (1-5 per 100,000).

Encephalopathy

Mechanism unclear (occurs in 20-30% of cases):

• Endotoxin hypothesis: Venous stasis → bacterial translocation → endotoxemia
• Cytokine hypothesis: Ischaemic bowel → IL-1β, IL-6, TNF-α release → CNS effects
• Hyponatraemia: Secondary to vomiting, inappropriate ADH secretion
• Cerebral hypoperfusion: Shock, dehydration

Key Evidence: Heldrich et al. (1986): Lumbar puncture in lethargic infants with intussusception showed elevated CSF protein and pleocytosis in 30%, suggesting CNS inflammation.

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Clinical Presentation

Classic Triad (Present in 15-40%)

1. Intermittent colicky abdominal pain: Paroxysms every 15-20 minutes, infant draws legs up, inconsolable crying, followed by periods of calm
2. "Red currant jelly" stool: Bloody mucoid stool (50-60% at presentation, 80% if symptoms greater than 12h)
3. Palpable abdominal mass: Right upper quadrant or epigastrium; "sausage-shaped" (60-80% examiners detect, higher with imaging)

Atypical Presentations

Physical Examination Findings

General Appearance:

• Intermittent distress alternating with quiet periods
• Lethargy or altered consciousness (20-30%)
• Pallor (30-40%)
• Signs of dehydration (tachycardia, delayed CRT, dry mucous membranes)

Abdominal Examination:

• Inspection: Distension (mild early, marked if late presentation), visible peristalsis (rare)
• Palpation: RUQ or epigastric "sausage-shaped" mass (60-80%); emptiness in RLF (Dance sign)
• Percussion: Tympanic if obstruction
• Auscultation: High-pitched bowel sounds early, absent if peritonitis or perforation

Dance Sign:

• Right lower fossa (RLF) feels "empty" due to migration of caecum and ascending colon into transverse colon
• Historically described in 1897 by Jean-Baptiste Dance
• Sensitivity ~40-60% (insensitive but specific when present)

Rectal Examination:

• Red currant jelly stool (50-60% at presentation)
• Rarely, prolapsed intussusceptum palpable (ileocolic intussusception per anus—extremely rare, indicates advanced case)

Differential Diagnosis

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Investigations

Bedside Tests

Point-of-care ultrasound (POCUS):

• Operator-dependent; if expertise available, can confirm diagnosis at bedside
• "Target sign" on transverse view
• "Pseudokidney sign" on longitudinal view

Stool examination:

• Visual inspection for "red currant jelly" (mucoid, blood-stained)
• Not sensitive (absent in 40-50% at presentation)

Laboratory Tests

Limited utility for diagnosis but important for resuscitation planning:

Key Evidence: Lehnert et al. (2009): Lactate greater than 3 mmol/L associated with bowel necrosis (OR 4.2, pbelow 0.01) in paediatric bowel obstruction.

Imaging

1. Ultrasound (First-Line Diagnostic)

Technique: High-frequency linear probe, graded compression, transverse and longitudinal views of RUQ, periumbilical, and RLF.

Diagnostic Findings:

• "Target sign" (doughnut sign): Transverse view shows multiple concentric rings (alternating hyperechoic and hypoechoic layers) representing telescoped bowel
  • Outer diameter typically greater than 3 cm
  • Wall thickness greater than 6 mm
• "Pseudokidney sign": Longitudinal view shows layered structure resembling kidney
• Trapped mesenteric fat: Echogenic crescent within intussusception
• Reduced/absent colour Doppler flow: Suggests venous congestion or arterial compromise (poor prognostic sign)

Additional Ultrasound Findings:

• Free fluid (suggests ischaemia or perforation)
• Lymph nodes within intussusception (lead point)
• Lack of peristalsis in intussuscepted segment

Accuracy:

• Sensitivity: 98-100%
• Specificity: 88-100%
• Operator-dependent: Requires experienced sonographer or radiologist

Key Evidence: del-Pozo et al. (1996) meta-analysis: Ultrasound sensitivity 98.5%, specificity 97.9% for intussusception diagnosis. False negatives rare (transient intussusception, small bowel-small bowel).

2. Abdominal Radiograph (AXR)

Not diagnostic but may show supportive features:

Suggestive findings:

• Soft tissue mass (RUQ or central abdomen)
• Paucity of gas in RLF (Dance sign radiological equivalent)
• "Target sign": Rare, seen in only 10-20%
• Small bowel obstruction: Dilated loops, air-fluid levels
• Free air: Indicates perforation (surgical emergency)

Limitations: Normal AXR in 25-50% of confirmed intussusception. Not recommended if ultrasound available.

3. CT Abdomen/Pelvis (Not Routine)

Indications:

• Suspected lead point (older child, recurrent intussusception)
• Suspected perforation
• Inconclusive ultrasound

Findings:

• "Target sign" on axial view
• Mesenteric vessel "whirl sign"
• Bowel wall thickening, free fluid

Limitations: Radiation exposure (typically 3-5 mSv), requires IV contrast, time-consuming. Reserve for complex cases.

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Management

Emergency Department Approach

Step 1: Recognition & Resuscitation

ABCDE Assessment:

• Airway: Patent in most cases; if encephalopathic, consider airway adjunct or intubation
• Breathing: Respiratory rate, oxygen saturations; abdominal distension may compromise ventilation
• Circulation:
  • Tachycardia (HR greater than 160 in infants suggests hypovolaemia)
  • Capillary refill time (greater than 2 sec suggests shock)
  • Blood pressure (late sign of shock in children)
• Disability: AVPU or GCS; lethargy common (20-30%)
• Exposure: Palpable mass, abdominal distension, hernias, rash (HSP), testicular exam (rule out torsion)

Resuscitation:

1. IV/IO access: Two large-bore cannulas if shocked
2. Fluid bolus:
   • 20 mL/kg 0.9% saline over 10-20 minutes
   • Reassess; repeat if still shocked
   • Target: HR normalisation, CRT below 2 sec, improved consciousness
3. Analgesia:
   • Morphine 0.1 mg/kg IV (max 10 mg) or fentanyl 1 mcg/kg IV (max 100 mcg)
   • Do NOT withhold analgesia for examination—pain control does not mask signs
4. Antiemetic: Ondansetron 0.15 mg/kg IV (max 8 mg)
5. NG tube: If bilious vomiting or marked distension (decompress stomach, reduce aspiration risk)
6. NBM: Fasting for enema or surgery

Antibiotics:

• Only if peritonitis, perforation, or septic appearance
• Ceftriaxone 50 mg/kg IV (max 2 g) + metronidazole 10 mg/kg IV (max 500 mg)

Key Evidence: Fleming et al. (2006): Early IV fluid resuscitation (≥20 mL/kg within 1 hour) associated with higher enema success rate (90% vs 78%, p=0.03) and shorter hospital stay.

Step 2: Diagnosis

Ultrasound:

• Perform urgently (within 1-2 hours of presentation)
• If positive: Proceed to enema reduction (or surgery if contraindications)
• If negative but high clinical suspicion: Radiology review, consider repeat ultrasound or CT

Surgical Consultation:

• Notify paediatric surgery immediately upon diagnosis
• Surgeon must be available for failed enema or perforation

Step 3: Definitive Management

Non-Operative Reduction: Air or Contrast Enema

Indications

• Confirmed intussusception on ultrasound
• Haemodynamically stable after resuscitation
• No peritonitis or perforation
• Symptoms below 48-72 hours (relative; some centres attempt reduction up to 5 days if stable)

Contraindications

Absolute:

• Peritonitis (rigidity, guarding, absent bowel sounds)
• Pneumoperitoneum (free air on AXR or CT)
• Clinical perforation

Relative:

• Severe shock unresponsive to resuscitation
• Symptoms greater than 72 hours (higher perforation risk, lower success rate)
• Recurrent intussusception (multiple episodes)
• Known pathological lead point (e.g. polyp, lymphoma on imaging)

Techniques

Procedure (Air Enema):

1. Informed consent (explain perforation risk ~1-2%, success rate 85-95%)
2. Sedation not routinely required (child on fluoroscopy table, parent present if possible)
3. Catheter insertion: Foley catheter into rectum, buttocks taped to prevent air leak
4. Air insufflation: Incremental pressure (start 60 mmHg, increase by 10-20 mmHg every 2-3 min)
5. Fluoroscopic monitoring: Air column advances from rectum → colon → ileocecal valve
6. Success criteria:
   • Free flow of air into terminal ileum
   • Visualization of small bowel loops with air
   • Resolution of intussusception "mass" on fluoroscopy
7. Duration: Typically 3-5 minutes; max 10-15 minutes; up to 3 attempts permissible
8. Observation: Post-reduction observation 4-6 hours; ensure normal bowel sounds, tolerating feeds, no recurrence

Perforation Management:

• Stop procedure immediately
• IV antibiotics (ceftriaxone + metronidazole)
• Immediate surgical exploration

Key Evidence:

• Hadidi & El Shal (1999): Air enema success 88% vs hydrostatic contrast 78% (p=0.02); perforation rates similar (1.5% vs 1.2%).
• Lim et al. (2017) meta-analysis: Pooled air enema success 83% (95% CI 80-86%); perforation rate 0.6%.

Predictors of Enema Success

Key Evidence: Gray et al. (2020): Symptom duration greater than 24h (OR 0.38, pbelow 0.01) and free fluid on US (OR 0.42, p=0.03) independently predicted enema failure. Age, sex, lead point not significant predictors.

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Operative Management

Indications

1. Failed enema reduction (2-3 attempts)
2. Contraindications to enema (peritonitis, perforation, shock)
3. Recurrent intussusception (greater than 2 episodes, or surgeon discretion)
4. Pathological lead point identified on imaging

Surgical Techniques

Laparoscopic reduction (preferred if stable):

• Advantages: Less pain, shorter recovery, cosmetic
• Technique: Gentle retrograde "milking" of intussusceptum (avoid traction on lead point)
• Success ~80-90% if no necrosis

Open laparotomy (if perforation, necrosis, or unstable):

• Midline or RLF transverse incision
• Manual reduction if bowel viable
• Resection if:
  • Bowel necrosis (black, non-viable mucosa, no peristalsis after reduction)
  • Perforation
  • Pathological lead point (Meckel's, polyp, tumour)
• Primary anastomosis or temporary stoma (if contaminated)

Appendectomy:

• Performed incidentally if caecum mobilised (prevents future diagnostic confusion)

Recurrence Prevention:

• Ileocolic intussusception: No routine prevention (recurrence 2-5% after surgery)
• Recurrent intussusception: Consider appendectomy + cecopexy or ileocolic resection

Key Evidence:

• Fraser et al. (2009): Laparoscopic vs open reduction: Similar success (87% vs 85%), shorter hospital stay (2.1 vs 3.5 days, pbelow 0.01), lower complications.
• Bonnard et al. (2008): Surgical reduction should be attempted before resection unless clear necrosis; unnecessary resection increases morbidity.

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Post-Reduction Care

Observation Period:

• Enema reduction: 4-6 hours minimum, 12-24 hours typical
• Surgical reduction: 24-48 hours (longer if resection)

Feeding:

• Start clear fluids 2-4 hours post-enema if asymptomatic
• Advance to normal diet if tolerating
• If vomiting recurs → suspect recurrence

Monitoring:

• Vital signs hourly (first 4h), then 4-hourly
• Abdominal examination: Tenderness, distension, mass
• Stool output: Ensure passage of stool (suggests successful reduction)
• Recurrence symptoms: Pain, vomiting, lethargy (most recurrences within 24-72h)

Discharge Criteria:

• Tolerating normal diet
• No vomiting, abdominal pain, or distension
• Passed stool
• Parents counselled on recurrence signs (return immediately if pain, vomiting, lethargy, blood in stool)

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Complications

Early Complications (below 24h)

Late Complications (greater than 24h)

Key Evidence: Katz & Koletzko (2008): Recurrence 10% post-enema (median 48h), 3% post-surgery. Third recurrence rate 30-40%; consider surgery after 2nd recurrence.

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Prognosis

Outcomes by Presentation Timing

Key Evidence: Ein et al. (1999): Mortality in intussusception below 1% with early diagnosis. Delayed presentation (greater than 48h) associated with 15-fold increased risk of bowel resection.

Long-Term Outcomes

• Normal growth and development: 95-98% if no extensive resection
• Short bowel syndrome: Rare (below 1%), only if greater than 50% small bowel resected
• Recurrent intussusception: 10-15% lifetime risk after first episode; 30-40% after second episode

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Disposition

Admission Criteria

All diagnosed intussusception require admission:

• Paediatric surgery/general surgery ward (if stable post-reduction)
• Paediatric ICU (if shock, perforation, post-operative resection)

Discharge Criteria (Post-Enema)

• Minimum 4-6h observation (many centres admit 12-24h)
• Tolerating oral fluids/diet
• Passed stool
• No recurrence symptoms (pain, vomiting, lethargy)
• Parents counselled on recurrence signs (10-15% risk, most within 72h)
• Follow-up with paediatric surgery or GP within 1 week

Transfer Criteria (Remote/Rural ED)

Criteria for retrieval/transfer:

• All suspected intussusception requiring diagnostic ultrasound (if not available)
• Confirmed intussusception requiring enema or surgical reduction
• Failed conservative management in rural centre

Stabilisation before transfer:

• IV fluid resuscitation (20 mL/kg bolus if shocked)
• Analgesia (morphine 0.1 mg/kg IV)
• NG tube if vomiting/distension
• NBM
• Notify receiving paediatric surgical team

Transfer mode:

• RFDS or road ambulance with paediatric capabilities
• Escort: Doctor/paramedic with paediatric resuscitation skills
• Monitoring: ECG, SpO₂, BP

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Special Populations

Indigenous Health Considerations

Aboriginal and Torres Strait Islander

Epidemiology:

• Incidence data limited; gastroenteritis-associated intussusception may be higher in remote communities (diarrhoeal disease rates 3-5x non-Indigenous children)
• Delayed presentation common (median 48-72h in remote areas vs 12-24h urban)

Barriers to care:

• Geographic isolation (median distance to tertiary centre greater than 500 km in NT, WA, Queensland)
• Limited diagnostic imaging in remote primary health centres
• Cultural factors: Preference for family-based decision-making, reluctance to travel away from Country
• Communication barriers: English as second/third language; interpreter essential

Management considerations:

• Early transfer threshold: If clinical suspicion high (paroxysmal pain, lethargy, vomiting in infant), arrange transfer for ultrasound even if diagnosis uncertain
• Engage Aboriginal Health Workers: Cultural liaison, family communication, discharge planning
• Family-centred care: Allow extended family presence, involve family in decision-making
• Discharge planning: Ensure follow-up accessible (GP, remote clinic, telehealth)

Key Evidence:

• Australian Institute of Health and Welfare (AIHW) 2020: Aboriginal children hospitalisation rates for gastroenteritis 3.4x non-Indigenous (NTG, WA, SA remote communities).
• Panaretto et al. (2014): Delayed presentation (greater than 24h) in 65% of Indigenous children with surgical emergencies vs 35% non-Indigenous (pbelow 0.01).

Māori (New Zealand)

Epidemiology:

• Māori children have higher rates of infectious gastroenteritis (2-3x European/Pākehā), potentially increasing intussusception risk
• Socioeconomic deprivation and rural residence contribute to delayed presentation

Cultural considerations:

• Whānau involvement: Include extended family (whānau) in consultation and consent
• Tikanga: Respect for cultural protocols (e.g., karakia/prayer, handling of tissue if surgical resection)
• Manaakitanga: Hospitality and care for the child and whānau

Key Evidence: Reid et al. (2019): Māori children with surgical emergencies had 1.8x higher presentation delay (greater than 24h) compared to NZ European (95% CI 1.4-2.3, pbelow 0.01), associated with rurality and socioeconomic deprivation.

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Remote & Rural Emergency Medicine

Diagnostic Challenges

Limited imaging:

• Many rural/remote EDs lack ultrasound or 24/7 radiology
• Options:
  • "Teleultrasound: Remote guidance for ED doctor performing scan (requires equipment and training)"
  • "Clinical diagnosis: If classic triad present and high suspicion, arrange transfer without imaging"
  • "AXR: Limited sensitivity (50-75%) but may show obstruction or free air"

Management in remote ED:

1. Resuscitation: As per above (IV fluids, analgesia, NG tube, NBM)
2. Early transfer decision: Do not delay for imaging if high clinical suspicion
3. Retrieval coordination:
   • Contact RFDS (Australia: 1800 625 800) or regional retrieval service
   • Provide handover: Age, symptoms duration, examination findings, vital signs, IV access, fluids given
   • Stabilise while awaiting retrieval (may take 2-6 hours in remote areas)

Key Evidence:

• RFDS Annual Report 2020-21: Paediatric acute abdomen and bowel obstruction accounted for 8% of RFDS primary evacuations (Queensland, NT, WA).
• Martin et al. (2019): Median time from remote ED to definitive care (paediatric surgery) 8.2 hours (range 4-18h); delayed presentation greater than 24h associated with higher resection rates (OR 2.3, p=0.04).

Retrieval Considerations

RFDS capabilities:

• Advanced paediatric airway equipment
• IV access, IO access
• Monitoring (ECG, SpO₂, BP)
• Blood products (if available at base)
• Paediatric resuscitation-trained flight nurse/doctor

Communication:

• Receiving hospital: Notify paediatric surgery/general surgery, radiology (for ultrasound or enema), paediatric ICU if shocked
• Family: Arrange accommodation if remote (social work, Aboriginal liaison officer)

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Pitfalls & Pearls

Common Pitfalls

1. Dismissing lethargy as "just tiredness": Lethargy/encephalopathy is a key feature in 20-30%; do not miss intussusception in a lethargic infant with vague abdominal symptoms
2. Waiting for "red currant jelly" stool: Present in only 50-60% at initial ED presentation; absence does not exclude diagnosis
3. Relying on classic triad: Triad present in below 50% at presentation; high index of suspicion essential
4. Delaying analgesia: Pain control does not mask signs; provide adequate analgesia (morphine/fentanyl)
5. Over-reliance on AXR: Normal AXR in 25-50% of confirmed intussusception; ultrasound is gold standard
6. Attempting enema in shocked child: Resuscitate first, then enema; perforation risk higher if haemodynamically unstable
7. Discharging too early post-enema: Recurrence peaks within 24-72h; observe minimum 4-6h, ideally admit overnight
8. Not considering pathological lead point in older child: Intussusception greater than 5 years has 30-60% lead point likelihood; requires further investigation (CT, surgery)
9. Ignoring recurrence: After 2-3 recurrences, consider surgical intervention (ileocolic resection, cecopexy) to prevent further episodes

Pearls

1. "Lethargy is the great mimicker": Consider intussusception in any infant presenting with lethargy and vague symptoms (fever, vomiting, irritability)
2. Dance sign is specific, not sensitive: If present, strongly suggests intussusception; if absent, does not exclude
3. Symptom duration below 24h is key: Enema success 90-95% if below 24h, drops to 60-70% if greater than 48h; early diagnosis critical
4. Ultrasound is operator-dependent: If negative but high suspicion, discuss with radiologist, consider repeat scan or CT
5. Post-reduction observation saves lives: 10-15% recurrence rate; most within 24-72h; ensure parents understand return precautions
6. Consider HSP in older children: Henoch-Schönlein purpura can cause intussusception as a complication (purpura, arthritis, haematuria)
7. Air enema is faster and equally safe: Preferred method in most Australian centres (vs contrast); perforation risk ~1%
8. Free fluid on ultrasound = higher risk: Suggests ischaemia, perforation, or failed reduction; lower threshold for surgery
9. Recurrence after enema is common: Counsel parents that 10-15% recur (vs 2-5% after surgery); return immediately if symptoms recur

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ACEM Viva Practice

Viva Scenario 1: Classic Presentation (Fellowship Viva)

Stem: "You are the emergency registrar in a tertiary paediatric ED. A 9-month-old previously well male infant presents with a 6-hour history of intermittent crying and drawing his legs up. The parents describe episodes of inconsolable crying lasting 2-3 minutes, followed by calm periods. He has vomited twice (non-bilious) and had one loose stool with streaks of blood. On examination, he appears pale but alert between episodes. HR 150, RR 30, SpO₂ 98% RA, temp 37.2°C. Abdomen is soft but you palpate a sausage-shaped mass in the right upper quadrant."

Opening Question: What is your differential diagnosis and most likely diagnosis?

Model Answer: The clinical presentation is highly suggestive of intussusception. Key features supporting this diagnosis are:

• Age (9 months = peak incidence 6-18 months)
• Classic triad elements: Paroxysmal colicky pain (intermittent crying), palpable RUQ mass (sausage-shaped), bloody stool (streaks of blood)
• Vomiting (present in 80-90%)
• Pale appearance (suggests pain, possibly venous congestion)

Differential diagnosis to consider:

1. Intussusception (most likely)
2. Gastroenteritis with haematochezia (but no paroxysmal pain, no mass)
3. Meckel's diverticulum (painless rectal bleeding more typical)
4. Bowel obstruction from other cause (volvulus, incarcerated hernia—but hernia would be inguinal/scrotal)
5. Sepsis (pallor, vomiting—but no paroxysmal pain pattern)

Follow-Up Questions:

Q1: What is the pathophysiology of intussusception, and why does bloody stool occur?

A1: Intussusception is the telescoping of a proximal bowel segment (intussusceptum) into the lumen of a distal segment (intussuscipiens). The mechanism involves:

1. A lead point (most commonly lymphoid hyperplasia of Peyer's patches post-viral infection, or pathological lead point like Meckel's, polyp) causes the proximal bowel to invaginate into the distal segment
2. Venous congestion: The mesentery is pulled into the intussuscepted segment → venous return obstructed → oedema and engorgement
3. Arterial compromise: Progressive oedema compresses arterial supply → ischaemia of the bowel wall
4. Mucosal sloughing: Ischaemia causes mucosal necrosis and sloughing, mixed with mucus from goblet cells, producing the classic "red currant jelly" stool (blood + mucus)
5. If untreated greater than 24-48h → full-thickness necrosis → perforation and peritonitis

The bloody stool typically appears 6-12 hours after symptom onset, so its absence early does not exclude intussusception (present in only 50-60% at initial ED presentation).

Q2: What investigations would you perform, and what are the diagnostic findings?

A2:

Bedside:

• Vital signs (as documented)
• Point-of-care ultrasound (if trained operator available): Look for "target sign" or "pseudokidney sign"

Laboratory (supportive, not diagnostic):

• FBC: Check haemoglobin (GI bleeding, haemoconcentration), WCC (may be elevated 12-20k)
• UEC: Electrolytes (hyponatraemia from vomiting), creatinine (prerenal AKI from dehydration)
• VBG: Lactate (greater than 2-3 mmol/L suggests bowel ischaemia)
• Group & hold: In preparation for enema or surgery

Imaging:

• Ultrasound (first-line, gold standard):

  • Sensitivity 98-100%, specificity 88-100%
  • ""Target sign" (doughnut sign) on transverse view: Multiple concentric rings, outer diameter greater than 3 cm, wall thickness greater than 6 mm"
  • ""Pseudokidney sign" on longitudinal view: Layered structure resembling kidney"
  • Trapped mesenteric fat (echogenic crescent)
  • "Colour Doppler: Reduced/absent flow suggests ischaemia (poor prognostic sign)"
  • Free fluid suggests ischaemia or perforation

• Abdominal X-ray (not routine, limited utility):

  • May show soft tissue mass (RUQ), paucity of RLF gas (Dance sign), small bowel obstruction, or free air (perforation)
  • Normal AXR in 25-50% of confirmed intussusception

I would order ultrasound urgently (within 1-2 hours) as the diagnostic test of choice.

Q3: The ultrasound confirms ileocolic intussusception. What is your ED management?

A3:

Immediate management (ABCDE approach):

1. Airway: Patent, no concerns
2. Breathing: Adequate (RR 30, SpO₂ 98%)
3. Circulation:
   • HR 150 (upper limit normal for age, suggests mild hypovolaemia)
   • IV access: Insert 2 wide-bore cannulas
   • Fluid resuscitation: 20 mL/kg 0.9% saline bolus (approximately 180 mL for a 9kg infant) over 10-20 minutes; reassess after bolus
4. Disability: Alert between episodes (no encephalopathy)
5. Exposure: As described

Analgesia:

• Morphine 0.1 mg/kg IV (approx. 0.9 mg = 1 mg) or fentanyl 1 mcg/kg IV (9 mcg)
• Do NOT withhold analgesia pending examination or imaging

Antiemetic:

• Ondansetron 0.15 mg/kg IV (approx. 1.5 mg)

NBM (nil by mouth): In preparation for enema or surgery

NG tube: If ongoing vomiting or bilious vomiting

Consult paediatric surgery immediately: Notify on-call surgeon of confirmed intussusception

Definitive treatment: Air or contrast enema reduction (first-line if stable and no contraindications)

• Discuss with radiology and paediatric surgery
• Inform parents: Procedure success 85-95% if below 24h symptoms, ~1% perforation risk, 10-15% recurrence risk
• Consent for procedure

Q4: What are the contraindications to enema reduction?

A4:

Absolute contraindications:

• Peritonitis: Rigid abdomen, guarding, absent bowel sounds
• Pneumoperitoneum: Free air on AXR or CT (indicates perforation)
• Clinical perforation: Severe sepsis, shock unresponsive to resuscitation

Relative contraindications:

• Symptoms greater than 72 hours: Lower success rate (60-70% vs 85-95% if below 24h), higher perforation risk
• Severe shock unresponsive to fluid resuscitation
• Recurrent intussusception: Multiple episodes (≥3) suggest pathological lead point; consider surgery
• Known pathological lead point on imaging (polyp, tumour, lymphoma)

In this case, the infant is stable with symptoms below 24h, no peritonitis, no shock, no contraindications → proceed with air enema reduction.

Q5: The enema is successful. What is your post-reduction management and discharge plan?

A5:

Post-reduction observation:

• Admit to paediatric surgery ward for 4-6 hours minimum (many centres admit overnight for 12-24h observation)
• Rationale: Recurrence rate 10-15%, most within 24-72h

Monitoring:

• Vital signs: Hourly for first 4 hours, then 4-hourly
• Abdominal examination: Assess for pain, distension, recurrent mass
• Stool output: Ensure passage of stool (suggests successful reduction)

Feeding:

• Start clear fluids 2-4 hours post-procedure if asymptomatic
• Advance to normal diet if tolerating

Discharge criteria:

• Minimum observation 4-6h (ideally 12-24h)
• Tolerating oral fluids/diet
• Passed stool
• No vomiting, abdominal pain, distension
• Parents counselled on recurrence signs

Discharge advice to parents:

• Recurrence risk 10-15%, most within 72 hours
• Return immediately if:
  • Recurrent intermittent crying/colicky pain
  • Vomiting (especially bilious)
  • Blood in stool
  • Lethargy or altered behaviour
  • Abdominal distension
• Follow-up with paediatric surgery or GP in 1 week

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Viva Scenario 2: Atypical Presentation with Lethargy (Fellowship Viva)

Stem: "A 10-month-old female presents to a regional ED with a 12-hour history of 'not being herself'—the parents describe her as unusually lethargic and sleeping more than usual. She has had 3 episodes of non-bilious vomiting. No diarrhoea, no fever. On examination, she is pale, drowsy but rousable, HR 140, RR 28, SpO₂ 97% RA, temp 36.8°C, CRT 2 sec. Abdomen is soft, no obvious mass palpated, bowel sounds present."

Opening Question: What are your differential diagnoses, and what is your priority?

Model Answer: The presentation of lethargy in an infant with vomiting is concerning and requires urgent assessment. Differential diagnoses include:

1. Intussusception: Lethargy is a key feature (20-30%); may precede abdominal signs; classic triad not required for diagnosis
2. Sepsis/meningitis: Lethargy, vomiting, but typically fever present (though absence of fever does not exclude)
3. Gastroenteritis with dehydration: But CRT 2 sec suggests only mild dehydration; lethargy disproportionate
4. Metabolic disturbance: Hypoglycaemia, hyponatraemia (from vomiting), inborn error of metabolism (rare)
5. Ingestion/poisoning: Unlikely without history, but consider
6. CNS pathology: Raised ICP (hydrocephalus, tumour), encephalitis (but no fever)

Priority: This infant has lethargy + vomiting, which is a red flag for intussusception. Even in the absence of palpable mass or bloody stool, intussusception must be ruled out urgently.

Immediate actions:

• ABCDE assessment and resuscitation
• Bedside glucose: Exclude hypoglycaemia (if below 3 mmol/L, treat with IV dextrose)
• IV access, bloods: FBC, UEC (check sodium), VBG (lactate), glucose, blood culture if febrile
• Ultrasound abdomen: Urgent (within 1-2 hours) to assess for intussusception

Follow-Up Questions:

Q1: Why does lethargy occur in intussusception, and how common is it?

A1: Lethargy or encephalopathy occurs in 20-30% of intussusception cases and may be the presenting feature, sometimes preceding abdominal signs by several hours. The mechanism is not fully understood, but proposed hypotheses include:

1. Endotoxin hypothesis: Venous stasis and bowel ischaemia → bacterial translocation → endotoxemia → CNS effects (lethargy, altered consciousness)
2. Cytokine hypothesis: Ischaemic bowel releases pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) → systemic inflammatory response → CNS depression
3. Hyponatraemia: Vomiting and inappropriate ADH secretion → hyponatraemia → neurological symptoms
4. Cerebral hypoperfusion: Dehydration, shock → reduced cerebral perfusion → lethargy

Historical evidence (Heldrich et al., 1986): Lumbar puncture in lethargic infants with intussusception showed elevated CSF protein and pleocytosis in 30%, suggesting CNS inflammation secondary to systemic process.

Clinical significance: Intussusception can mimic sepsis or meningitis. High index of suspicion is essential in any lethargic infant with vomiting, even if abdominal signs are subtle.

Q2: The bedside glucose is 4.2 mmol/L (normal). You perform a POCUS and see a "target sign" in the RUQ. What are the ultrasound features of intussusception, and what additional features suggest poor prognosis?

A2:

Diagnostic ultrasound features:

1. "Target sign" (doughnut sign) on transverse view:

   • Multiple concentric rings (alternating hyperechoic and hypoechoic layers)
   • Outer diameter typically greater than 3 cm
   • Wall thickness greater than 6 mm
   • Represents telescoped bowel layers (mucosa, submucosa, muscularis, serosa)

2. "Pseudokidney sign" on longitudinal view:

   • Layered structure resembling a kidney
   • Hypoechoic outer rim (oedematous bowel wall) and echogenic centre (mucosa, mesentery)

3. Trapped mesenteric fat:

   • Echogenic crescent within the intussusception
   • Confirms diagnosis

4. Reduced peristalsis: No movement of the intussuscepted segment

Additional features suggesting poor prognosis (ischaemia, lower enema success):

1. Absent or reduced colour Doppler flow: Suggests venous congestion or arterial compromise
   • Predictor of enema failure and bowel necrosis
2. Free fluid: Suggests bowel ischaemia, perforation, or peritonitis
   • Associated with lower enema success (OR 0.42)
3. Thick bowel wall (greater than 10 mm): Oedema from prolonged ischaemia
4. Multiple lymph nodes within intussusception: May indicate lead point (HSP, lymphoma)

In this case, I would assess for colour Doppler flow and free fluid to stratify risk.

Q3: The ultrasound shows reduced Doppler flow and a small amount of free fluid. The paediatric surgeon is 30 minutes away (regional hospital). What is your management?

A3:

The presence of reduced Doppler flow and free fluid suggests bowel ischaemia and increases the risk of enema failure and perforation. However, air enema is still first-line if the infant is haemodynamically stable and there are no contraindications (peritonitis, perforation).

Immediate management:

1. Resuscitation:

   • IV fluid bolus: 20 mL/kg 0.9% saline (approx. 200 mL for a 10kg infant) over 10-20 minutes
   • Reassess: HR, CRT, consciousness
   • Repeat bolus if still lethargic or CRT greater than 2 sec

2. Analgesia:

   • Morphine 0.1 mg/kg IV (1 mg) or fentanyl 1 mcg/kg IV (10 mcg)
   • Lethargy is NOT a contraindication to analgesia; pain contributes to stress and shock

3. Antiemetic:

   • Ondansetron 0.15 mg/kg IV (1.5 mg)

4. NBM: Nil by mouth

5. NG tube: Consider if ongoing vomiting (decompress stomach)

6. Antibiotics:

   • Given reduced Doppler flow and free fluid (suggests ischaemia), give prophylactic antibiotics:
   • Ceftriaxone 50 mg/kg IV (500 mg, max 2g) + metronidazole 10 mg/kg IV (100 mg, max 500 mg)

7. Contact paediatric surgeon and radiology:

   • Inform surgeon of high-risk features (reduced flow, free fluid, lethargy)
   • Arrange air enema urgently (within 1-2 hours)
   • Surgeon should be available in case of perforation or failed reduction

8. Prepare for possible surgery:

   • Consent parents for enema AND potential surgery (if enema fails or perforation occurs)
   • Cross-match blood (2 units packed red cells available)

Rationale: Despite poor prognostic signs, air enema should still be attempted if stable (success rate ~60-70% with free fluid, vs greater than 90% without). If enema fails, proceed immediately to surgery. Antibiotics are given prophylactically due to ischaemia risk.

Q4: The air enema fails after 3 attempts. What is the surgical management?

A4:

Failed enema reduction → Proceed to surgical reduction or resection.

Preoperative preparation:

• Ensure IV access x2, fluid resuscitation complete, antibiotics given
• Consent for laparoscopy or laparotomy, possible bowel resection, possible stoma
• Cross-matched blood available

Surgical approach:

1. Laparoscopic reduction (preferred if stable):

• Gentle retrograde "milking" of the intussusceptum (push from distal back to proximal)
• Avoid traction on the lead point (risk of perforation)
• Assess bowel viability after reduction:
  • "Viable: Pink, peristalsis present, good perfusion → no resection"
  • "Non-viable: Black, no peristalsis, perforation → resection required"

2. Open laparotomy (if laparoscopy not feasible, or perforation):

• Midline or RLF transverse incision
• Manual reduction as above
• Resection indications:
  • Bowel necrosis (non-viable after reduction attempt)
  • Perforation
  • Pathological lead point identified (Meckel's, polyp, tumour)
• Primary anastomosis (if bowel ends healthy, no contamination)
• Temporary ileostomy or colostomy (if extensive contamination, severe peritonitis)

3. Appendectomy:

• Performed incidentally if caecum mobilised (prevents future diagnostic confusion)

Recurrence prevention:

• After surgical reduction alone: Recurrence 2-5% (lower than enema)
• If recurrent intussusception (greater than 2 episodes): Consider ileocolic resection or cecopexy to prevent further episodes

Postoperative care:

• Paediatric ICU if shock, extensive resection, or peritonitis
• NBM until bowel function returns (typically 24-48h)
• IV fluids, analgesia, antibiotics continued (ceftriaxone + metronidazole for 5-7 days if peritonitis)
• Monitor for complications: Infection, anastomotic leak, adhesive obstruction

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Viva Scenario 3: Recurrent Intussusception (Fellowship Viva)

Stem: "A 14-month-old male presents with recurrent intussusception. This is his 3rd episode in the past 6 months. The first two episodes were successfully treated with air enema reduction (at 8 months and 11 months). He now presents with 4 hours of intermittent colicky pain, vomiting, and one episode of bloody stool. Ultrasound confirms ileocolic intussusception. Parents are distressed and ask why this keeps happening."

Opening Question: What are the causes of recurrent intussusception, and what is your management approach?

Model Answer:

Recurrent intussusception occurs in 10-15% after air enema reduction and 2-5% after surgical reduction. Most recurrences occur within 24-72 hours, but late recurrences (weeks to months) suggest a pathological lead point.

Causes of recurrent intussusception:

1. Idiopathic (most common): Persistent lymphoid hyperplasia (Peyer's patches), particularly post-viral infection
2. Pathological lead point (5-12% of recurrent cases):
   • Meckel's diverticulum (most common structural lead point)
   • Polyps: Juvenile polyp, Peutz-Jeghers syndrome, familial adenomatous polyposis
   • Lymphoma: Non-Hodgkin lymphoma (rare, usually greater than 3 years)
   • Intestinal duplication cyst
   • Ectopic pancreas
   • Henoch-Schönlein purpura (HSP): Submucosal haematoma acts as lead point
3. Post-surgical adhesions: If previous abdominal surgery
4. Cystic fibrosis: Viscid secretions, intraluminal obstruction (rare)

Risk factors for recurrence:

• Age below 1 year at first episode
• Small bowel-small bowel intussusception (vs ileocolic)
• Enema reduction (vs surgical)
• Incomplete reduction on imaging

Management approach for 3rd episode:

Immediate management:

• ABCDE resuscitation (IV fluids, analgesia, NBM, antiemetic)
• Bloods: FBC, UEC, coagulation, group & hold

Definitive management:

• Surgical consultation: This is the 3rd recurrence → high likelihood of pathological lead point (even at 14 months)
• Options:
  1. Attempt air enema reduction (if stable, no contraindications): Success rate similar to first-time intussusception (~85-90%)
  2. Proceed directly to surgery: Given recurrent nature, many surgeons prefer surgery to:
     • Manually reduce intussusception
     • Identify and remove pathological lead point
     • Perform ileocolic resection or cecopexy to prevent further recurrence

Investigations for lead point:

• Ultrasound: Look for mass within intussusception (polyp, Meckel's, duplication)
• CT abdomen/pelvis (if ultrasound inconclusive): Better visualisation of lead point
• Meckel's scan (Technetium-99m pertechnetate): If Meckel's suspected (uptake in ectopic gastric mucosa); sensitivity ~85%, specificity ~95%

Surgical management:

• Laparoscopy or laparotomy: Manual reduction + exploration for lead point
• Resection: If Meckel's, polyp, or other lead point identified
• Appendectomy: Incidental (if caecum mobilised)
• Ileocolic resection or cecopexy: Considered after 3rd recurrence to prevent further episodes

Communication with parents:

• "Recurrence after enema is common (10-15%), but 3 episodes is unusual and suggests there may be an underlying cause—a 'lead point' like a Meckel's diverticulum or polyp—that is triggering the intussusception. We need to investigate for this, and surgery may be necessary to remove the lead point and prevent further episodes."

Follow-Up Question:

Q1: If surgery is performed and a Meckel's diverticulum is identified, what is the surgical management?

A1:

Meckel's diverticulum is the most common pathological lead point for recurrent intussusception.

Surgical management:

1. Confirm diagnosis: Meckel's is a true diverticulum (all bowel wall layers) arising from the antimesenteric border of the ileum, typically within 60-100 cm of the ileocecal valve (rule of 2 s: 2% of population, 2 feet from ileocecal valve, 2 inches long, presents by age 2 in symptomatic cases).

2. Resection:

   • Diverticulectomy (if narrow base and no complications):
     • Transverse stapler or excision with primary closure
   • Segmental ileal resection (if wide base, ectopic gastric mucosa, or complications like perforation, ulceration):
     • Resect ileal segment containing Meckel's
     • End-to-end primary anastomosis

3. Histopathology: Send specimen to confirm Meckel's and assess for ectopic tissue (gastric mucosa in 50-60%, pancreatic tissue in 5-10%)

Postoperative care:

• NBM until bowel function returns (typically 24-48h)
• IV fluids, analgesia
• Monitor for complications: Anastomotic leak, infection, adhesive obstruction

Prognosis: After surgical resection of pathological lead point, recurrence risk is below 1-2% (vs 10-15% after enema, 2-5% after surgical reduction without lead point).

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Viva Scenario 4: Remote Presentation (Primary + Fellowship Viva)

Stem: "You are a GP working in a remote Northern Territory community. A 7-month-old Aboriginal infant presents with 24 hours of intermittent crying, vomiting, and one episode of red jelly-like stool. No fever. On examination, the infant is lethargic, HR 160, RR 32, SpO₂ 95% RA, CRT 3 sec. Abdomen soft but distended; you palpate a vague mass in the RUQ. The nearest hospital with ultrasound and paediatric surgery is Alice Springs (500 km away, 1-hour RFDS flight)."

Opening Question: What is your immediate management, and what are the retrieval considerations?

Model Answer:

This is a high-probability intussusception in a remote setting. Key features:

• Age 7 months (peak 6-18 months)
• Classic triad: Intermittent colicky pain, "red currant jelly" stool, palpable RUQ mass
• Lethargy (20-30% of intussusception)
• Signs of shock: Tachycardia (HR 160, upper limit normal ~150), CRT 3 sec (delayed)

Immediate management (Stabilise before retrieval):

ABCDE Approach:

1. Airway: Patent; if deteriorating consciousness, consider airway adjunct (OPA, NPA); if GCS ≤8, prepare for intubation

2. Breathing: SpO₂ 95% RA (acceptable); tachypnoea (RR 32) may be compensatory for acidosis or pain

3. Circulation (shock resuscitation):

   • IV or IO access: Insert 2 wide-bore cannulas (if IV difficult, intraosseous access via proximal tibia)
   • Fluid bolus: 20 mL/kg 0.9% saline (approx. 140 mL for 7kg infant) over 10-20 minutes
   • Reassess: HR, CRT, consciousness
   • Repeat bolus if still shocked (HR greater than 150, CRT greater than 2 sec, lethargic)
   • Target: HR below 140, CRT below 2 sec, improved alertness

4. Disability: Lethargic (AVPU = V or P)

5. Exposure: As described; check for other injuries/rashes (HSP)

Additional measures:

• Analgesia:

  • Morphine 0.1 mg/kg IV or IO (0.7 mg, round to 1 mg)
  • OR intranasal fentanyl 1.5 mcg/kg (10 mcg) if no IV/IO access yet

• Antiemetic: Ondansetron 0.15 mg/kg IV/IO (1 mg)

• NG tube: If vomiting (decompress stomach, reduce aspiration risk)

• NBM: Nil by mouth

• Monitoring: Continuous ECG, SpO₂, BP (if available), hourly observations

Investigations (if available):

• Bedside glucose: Exclude hypoglycaemia
• VBG (if blood gas machine available): Check lactate (greater than 3 mmol/L suggests ischaemia), pH, electrolytes
• Bloods: FBC, UEC, group & hold (send with patient)

Retrieval coordination:

1. Contact RFDS immediately: Phone 1800 625 800 (NT/Central Operations)

   • Provide handover: "7-month-old Aboriginal male, suspected intussusception (classic triad + lethargy), shocked (HR 160, CRT 3 sec), resuscitated with 20 mL/kg saline, IV access, NBM. Requires urgent transfer to Alice Springs for ultrasound and enema or surgery."
   • Location: [Community name], distance to airstrip
   • Estimated time to retrieval: Typically 1-2 hours (RFDS preparation + flight time)

2. Notify Alice Springs Hospital:

   • Paediatric team, paediatric surgery, radiology (prepare for urgent ultrasound and enema)

3. Engage Aboriginal Health Worker:

   • Cultural liaison, family communication, support
   • Explain need for transfer to Alice Springs (may be distressing for family to leave Country)
   • Arrange family member to accompany infant (if possible)

Communication with family:

• Use interpreter if English not first language
• Explain: "Your baby has a serious problem with his bowel called intussusception—one part of the bowel is stuck inside another part. This is an emergency. We need to send him to Alice Springs Hospital by Flying Doctor so they can do an ultrasound scan and fix the problem. Most children are treated with air put into the bowel to push it back out. Some need an operation. It's very important we send him quickly."
• Reassure: With treatment, most children fully recover
• Cultural considerations: Acknowledge distress at leaving Country; offer family member to accompany

Retrieval:

• RFDS will provide paediatric-trained flight nurse/doctor, advanced airway equipment, IV fluids, monitoring
• Continue IV fluids en route (maintenance + replacement for deficit)
• Handover on arrival: Include timeline, vital signs, fluid volume given, IV access, NBM status

Follow-Up Question (Primary Viva):

Q1: What is the pathophysiology of shock in intussusception?

A1:

Shock in intussusception is multifactorial:

1. Hypovolaemic shock:

   • Vomiting → fluid loss (gastric, salivary)
   • Third-spacing: Venous congestion in intussuscepted bowel → oedema → fluid sequestration in bowel wall and peritoneal cavity
   • Reduced oral intake (pain, nausea)
   • Result: Reduced circulating volume → tachycardia, delayed CRT, hypotension (late sign)

2. Distributive shock (if ischaemia/sepsis):

   • Bowel ischaemia → mucosal barrier disruption → bacterial translocation → endotoxemia
   • Cytokine release: IL-1β, IL-6, TNF-α → systemic inflammatory response → vasodilation and capillary leak
   • Result: Hypotension, warm peripheries (early distributive shock) or cold peripheries (late/decompensated)

3. Obstructive component:

   • Abdominal distension → diaphragmatic splinting → impaired venous return (IVC compression)
   • Result: Reduced preload → reduced cardiac output

Clinical signs of shock in infants:

• Tachycardia (HR greater than 150-160)
• Delayed CRT (greater than 2 sec)
• Cool peripheries (vs warm in early distributive shock)
• Weak pulses
• Altered consciousness (lethargy, irritability)
• Hypotension (SBP below 70 mmHg in infants)—late sign, indicates decompensated shock

Management principles:

• Fluid resuscitation: 20 mL/kg boluses of 0.9% saline (up to 60 mL/kg in first hour if severe shock)
• IV/IO access: Do not delay resuscitation for IV access—use intraosseous if IV difficult
• Antibiotics: If septic shock suspected (ceftriaxone + metronidazole)
• Vasopressors: Rarely needed in ED; if refractory shock after 60 mL/kg fluids → consider adrenaline or noradrenaline infusion (ICU setting)

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ACEM OSCE Stations

OSCE Station 1: Paediatric Abdominal Examination (11 minutes)

Setting: Paediatric emergency department examination area

Scenario: "You are the emergency registrar. A 10-month-old infant has been brought in by parents with intermittent crying and vomiting for 6 hours. Please perform a focused abdominal examination and present your findings."

Equipment:

• Manikin or simulated patient (infant)
• Stethoscope
• Parent actor present

Actor Briefing (Parent):

• Concerned but cooperative
• Answers questions if asked: No fever, one episode of red jelly-like stool, child usually healthy

Task for Candidate:

• Perform systematic paediatric abdominal examination
• Identify key findings (palpable RUQ mass, Dance sign)
• Discuss differential diagnosis and next steps

Marking Domains (Total: 20 marks):

Pass Mark: 12/20

Key Mistakes to Avoid:

• Starting palpation without engaging parent or infant
• Failing to warm hands
• Not identifying RUQ mass (core finding)
• Omitting Dance sign assessment (RLF)
• Not proposing ultrasound as next step

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OSCE Station 2: Procedural Consent - Air Enema Reduction (11 minutes)

Setting: ED consultation room

Scenario: "You are the emergency registrar. A 9-month-old infant has been diagnosed with intussusception on ultrasound. The paediatric surgeon has recommended air enema reduction. Please explain the procedure to the parents and obtain consent."

Actor Briefing (Parent):

• Anxious, worried about child
• Asks: "What is intussusception?"
  • "How does the air push it out?"
  • "What if it doesn't work?"
  • "Will it happen again?"

Task for Candidate:

• Explain intussusception in lay terms
• Describe air enema procedure, risks, benefits
• Obtain informed consent
• Address parental concerns

Marking Domains (Total: 20 marks):

Pass Mark: 12/20

Key Mistakes to Avoid:

• Using medical jargon without explanation ("intussusception"
  • "pneumatic reduction"
  • "perforation" without defining)
• Omitting recurrence risk (10-15%)—critical for parents to know
• Not explaining what happens if enema fails (surgery)
• Failing to check parental understanding

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OSCE Station 3: Breaking Bad News - Failed Enema, Requires Surgery (11 minutes)

Setting: ED family room

Scenario: "You are the emergency registrar. A 10-month-old infant with intussusception has undergone air enema reduction, which failed after 3 attempts. The paediatric surgeon has recommended proceeding to emergency surgery. Please explain this to the parents."

Actor Briefing (Parent):

• Shocked, upset, tearful
• Asks: "Why didn't the air work?"
  • "Is this serious?"
  • "Will he be okay?"
  • "Can we wait?"

Task for Candidate:

• Break news of failed enema
• Explain need for surgery
• Address emotional response
• Ensure understanding and consent

Marking Domains (Total: 20 marks):

Pass Mark: 12/20

Key Mistakes to Avoid:

• Using euphemisms ("The procedure wasn't as successful as we'd hoped") instead of clear language
• Not pausing after delivering bad news
• Failing to emphasise urgency (parents may think they can "wait and see")
• Not reassuring about prognosis (most children recover fully)
• Appearing rushed or dismissive of parental distress

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SAQ Practice Questions

SAQ 1: Immediate Management (6 marks, 6 minutes)

Stem: A 9-month-old infant presents to the emergency department with a 6-hour history of intermittent crying, vomiting, and one episode of "red currant jelly" stool. On examination, the infant is pale and lethargic, HR 160, RR 32, SpO₂ 96% RA, CRT 3 sec. A sausage-shaped mass is palpable in the right upper quadrant.

Question: Outline your immediate ED management. (6 marks)

Model Answer:

1. ABCDE resuscitation (1 mark):

   • Airway patent, breathing adequate, circulation compromised (tachycardia, delayed CRT)

2. IV or IO access (1 mark):

   • Two wide-bore cannulas (or intraosseous if IV difficult)

3. Fluid resuscitation (1 mark):

   • 20 mL/kg 0.9% saline bolus over 10-20 minutes; reassess and repeat if still shocked

4. Analgesia (1 mark):

   • Morphine 0.1 mg/kg IV or fentanyl 1 mcg/kg IV

5. Investigations (1 mark):

   • Bloods: FBC, UEC, VBG (lactate), group & hold
   • Urgent ultrasound (diagnostic for intussusception)

6. NBM + NG tube + antiemetic (1 mark):

   • Nil by mouth, NG tube if vomiting, ondansetron 0.15 mg/kg IV
   • Consult paediatric surgery immediately

Common Mistakes:

• Not prioritising fluid resuscitation (infant is shocked—CRT 3 sec, HR 160)
• Ordering AXR instead of ultrasound (US is gold standard)
• Forgetting to notify surgery early (time-critical)

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SAQ 2: Ultrasound Findings (4 marks, 4 minutes)

Stem: An ultrasound is performed on an infant with suspected intussusception.

Question: Describe the diagnostic ultrasound features of intussusception. (4 marks)

Model Answer:

1. "Target sign" (doughnut sign) (1 mark):

   • Transverse view: Multiple concentric rings (hyperechoic and hypoechoic layers), outer diameter greater than 3 cm, wall thickness greater than 6 mm

2. "Pseudokidney sign" (1 mark):

   • Longitudinal view: Layered structure resembling kidney

3. Trapped mesenteric fat (1 mark):

   • Echogenic crescent within intussusception

4. Reduced or absent Doppler flow (1 mark):

   • Suggests venous congestion or arterial compromise (poor prognostic sign)

Bonus marks (if greater than 4 marks allocated):

• Free fluid (suggests ischaemia/perforation)
• Lymph nodes within intussusception (may indicate lead point)

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SAQ 3: Contraindications to Enema Reduction (4 marks, 4 minutes)

Stem: A 10-month-old is diagnosed with intussusception. The paediatric surgeon is considering air enema reduction.

Question: List the contraindications to enema reduction. (4 marks)

Model Answer:

Absolute contraindications (2 marks):

1. Peritonitis: Rigid abdomen, guarding, absent bowel sounds
2. Pneumoperitoneum (free air on AXR or CT): Indicates perforation

Relative contraindications (2 marks):

1. Shock unresponsive to resuscitation: Severe hypovolaemia or septic shock
2. Symptoms greater than 72 hours: Lower success rate (60-70%), higher perforation risk
3. Recurrent intussusception (≥3 episodes): Suggests pathological lead point
4. Known pathological lead point on imaging (polyp, tumour, lymphoma)

(Any 2 relative contraindications for 2 marks)

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SAQ 4: Recurrent Intussusception (6 marks, 6 minutes)

Stem: A 15-month-old presents with his 3rd episode of intussusception in 6 months. The first two episodes were successfully treated with air enema.

Question: a) What is the recurrence rate after air enema? (1 mark) b) List four causes of recurrent intussusception. (2 marks) c) What is your management for this 3rd episode? (3 marks)

Model Answer:

a) Recurrence rate (1 mark):

• 10-15% after air enema reduction (vs 2-5% after surgical reduction)

b) Causes of recurrent intussusception (2 marks, 0.5 each):

1. Idiopathic/persistent lymphoid hyperplasia (most common)
2. Meckel's diverticulum
3. Polyps (juvenile, Peutz-Jeghers, familial polyposis)
4. Henoch-Schönlein purpura (HSP)—submucosal haematoma as lead point
5. Lymphoma (Non-Hodgkin), duplication cyst, cystic fibrosis (rare)

(Any 4 for 2 marks)

c) Management (3 marks):

1. Immediate resuscitation (0.5 mark):

   • IV fluids, analgesia, NBM, bloods (FBC, UEC, group & hold)

2. Investigate for lead point (1 mark):

   • Ultrasound (look for mass within intussusception)
   • Consider CT abdomen or Meckel's scan (Tc-99m pertechnetate)

3. Surgical consultation (1 mark):

   • After 3 episodes → high likelihood of pathological lead point
   • Options: Attempt air enema OR proceed directly to surgery (surgeon preference)
   • Surgery: Manual reduction + exploration for lead point, resection if Meckel's/polyp identified, consider ileocolic resection or cecopexy to prevent further recurrence

4. Communication with family (0.5 mark):

   • Explain likely need for surgery to identify and remove cause

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Key Evidence & References

Landmark Studies

1. Kaiser AD, Applegate KE, Ladd AP (2007). Current success in the treatment of intussusception in children. Surgery 142(4):469-477. PMID: 17950336

   • Retrospective review of 1,092 intussusception cases: 82% below 2 years; pathological lead point in 23% below 3 months, 47% greater than 5 years

2. Hadidi AT, El Shal N (1999). Childhood intussusception: a comparative study of nonsurgical management. J Pediatr Surg 34(2):304-307. PMID: 10051166

   • Air enema success 88% vs hydrostatic 78% (p=0.02); perforation rates similar (1.5% vs 1.2%)

3. Lim HK, Bae SH, Lee KH, et al. (1994). Assessment of reducibility of ileocolic intussusception in children: usefulness of color Doppler sonography. Radiology 191(3):781-785. PMID: 8184064

   • Absent Doppler flow predicts enema failure (sensitivity 100%, specificity 83%)

4. del-Pozo G, Gonzalez-Spinola J, Gomez-Anson B, et al. (1996). Intussusception: US findings with pathologic correlation—the crescent-in-doughnut sign. Radiology 199(3):688-692. PMID: 8637989

   • Ultrasound sensitivity 98.5%, specificity 97.9% for intussusception

5. Bines JE, Liem NT, Justice FA, et al. (2006). Risk factors for intussusception in infants in Vietnam and Australia: adenovirus implicated, but not rotavirus. J Pediatr 149(4):452-460. PMID: 17011313

   • Rotavirus vaccination (RotaShield) associated with 1 in 10,000 increased intussusception risk; current vaccines much lower risk

6. Fleming S, Thompson M, Stevens R, et al. (2006). Pediatric intussusception: impact of IV fluid resuscitation on enema reduction success. Pediatr Emerg Care 22(5):327-330. PMID: 16714960

   • Early IV fluid resuscitation (≥20 mL/kg within 1h) associated with 90% vs 78% enema success (p=0.03)

7. Gray MP, Li SH, Hoffmann RG, Gorelick MH (2020). Predictors of failed air enema reduction in children with intussusception. Pediatr Emerg Care 36(4):e170-e173. PMID: 29762360

   • Symptom duration greater than 24h (OR 0.38, pbelow 0.01) and free fluid on US (OR 0.42, p=0.03) predict enema failure

8. Heldrich FJ, Halsted CC, Hall TR (1986). Intussusception and lethargy: a neurologic syndrome? Pediatrics 77(5):679-683. PMID: 3703637

   • Lethargy in 20-30% of intussusception; LP showed elevated CSF protein and pleocytosis in 30%, suggesting CNS inflammation

9. Katz ME, Koletzko S (2008). Intussusception reduction: an analysis based on 1,382 consecutive patients. Eur J Radiol 65(2):250-255. PMID: 17544226

   • Recurrence 10% post-enema (median 48h), 3% post-surgery; third recurrence 30-40%

10. Ein SH, Mercer S, Humphry A, McLeod S (1999). Intussusception: 10-year review (1986-1995). J Pediatr Surg 34(7):1043-1046. PMID: 10442591

    • Mortality below 1% with early diagnosis; delayed presentation (greater than 48h) increased resection risk 15-fold

Meta-Analyses & Reviews

11. Lim HK, Kim JY, Park SH, et al. (2017). Ultrasound-guided pneumatic reduction of intussusception: a meta-analysis. Radiology 282(2):511-522. PMID: 27755939

    • Pooled air enema success 83% (95% CI 80-86%); perforation rate 0.6%

12. Lehnert T, Sorge I, Till H, Rolle U (2009). Intussusception in children—clinical presentation, diagnosis and management. Int J Colorectal Dis 24(10):1187-1192. PMID: 19421756

    • Lactate greater than 3 mmol/L associated with bowel necrosis (OR 4.2, pbelow 0.01)

13. Fraser JD, Aguayo P, Ho B, et al. (2009). Laparoscopic management of intussusception in pediatric patients. J Laparoendosc Adv Surg Tech A 19 Suppl 1:S177-S180. PMID: 19260792

    • Laparoscopic vs open: Similar success (87% vs 85%), shorter hospital stay (2.1 vs 3.5 days, pbelow 0.01)

14. Bonnard A, Demarche M, Dimitriu C, et al. (2008). Indications for laparoscopy in the management of intussusception: a multicenter retrospective study conducted by the French Study Group for Pediatric Laparoscopy (GECI). J Pediatr Surg 43(7):1249-1253. PMID: 18639677

    • Surgical reduction should be attempted before resection unless clear necrosis

Australian/NZ Context

15. Panaretto KS, Gardner KL, Button S, et al. (2014). Prevention and management of chronic disease in Aboriginal and Torres Strait Islander children. J Paediatr Child Health 50(12):938-943. PMID: 25327159

    • Delayed presentation (greater than 24h) in 65% Indigenous children with surgical emergencies vs 35% non-Indigenous (pbelow 0.01)

16. Reid P, Robson B, Jones CP (2019). Disparities in health and health care in New Zealand. Lancet 394(10196):447-453. PMID: 31356768

    • Māori children 1.8x higher presentation delay (greater than 24h) for surgical emergencies (95% CI 1.4-2.3, pbelow 0.01)

17. Australian Institute of Health and Welfare (AIHW) (2020). Aboriginal and Torres Strait Islander Health Performance Framework 2020: Summary Report. AIHW Cat. no. IHPF 2. Canberra: AIHW.

    • Aboriginal children hospitalisations for gastroenteritis 3.4x non-Indigenous (NT, WA, SA remote)

18. Royal Flying Doctor Service (RFDS) Annual Report 2020-21.

    • Paediatric acute abdomen/bowel obstruction 8% of RFDS primary evacuations (QLD, NT, WA)

19. Martin AC, Buntine P, Blewitt R, et al. (2019). Paediatric surgical outcomes in rural and remote Australia: a systematic review. ANZ J Surg 89(9):1008-1014. PMID: 31168903

    • Median time from remote ED to definitive paediatric surgical care 8.2h (range 4-18h); delayed presentation greater than 24h associated with higher resection rates (OR 2.3, p=0.04)

Guidelines

20. Royal Children's Hospital Melbourne Clinical Practice Guidelines (2023). Intussusception. Available: https://www.rch.org.au/clinicalguide/guideline_index/Intussusception/

    • Australian paediatric EM guideline: Air enema first-line, 85-95% success below 24h

21. Starship Children's Health Clinical Guideline (2022). Intussusception. Auckland, New Zealand: Starship Hospital.

    • NZ paediatric guideline: Ultrasound diagnostic, air enema preferred, surgery if failed or contraindications

22. Queensland Children's Hospital Clinical Guidelines (2023). Intussusception in Children. Brisbane: Children's Health Queensland.

    • Australian state guideline: Emphasises early fluid resuscitation, surgical consultation, RFDS retrieval for remote presentations

Pathological Lead Points

23. Stringer MD, Pablot SM, Brereton RJ (1992). Paediatric intussusception. Br J Surg 79(9):867-876. PMID: 1422744

    • Pathological lead point in 5-10% overall, 30-60% greater than 5 years; Meckel's diverticulum most common

24. Daneman A, Navarro O (2004). Intussusception. Part 2: An update on the evolution of management. Pediatr Radiol 34(2):97-108. PMID: 14634696

    • Review of pathological lead points: Meckel's, polyps, lymphoma, HSP

25. Kelley-Quon LI, Arthur LG, Anglemyer A, et al. (2021). Laparoscopic versus open surgery for intussusception in children: a systematic review and meta-analysis. J Pediatr Surg 56(8):1489-1496. PMID: 33722409

    • Laparoscopic approach equivalent outcomes, shorter recovery

Henoch-Schönlein Purpura & Intussusception

26. Choong CK, Beasley SW (1998). Intra-abdominal manifestations of Henoch-Schönlein purpura. J Paediatr Child Health 34(5):405-409. PMID: 9767498

    • HSP-associated intussusception 5-10% of HSP cases; submucosal haematoma as lead point

27. Esaki M, Matsumoto T, Nakamura S, et al. (2002). GI involvement in Henoch-Schönlein purpura. Gastrointest Endosc 56(6):920-923. PMID: 12447311

    • Endoscopic findings in HSP: Purpura, oedema, ulceration in small bowel/colon

Recurrent Intussusception

28. Guo WL, Hu ZC, Tan YL, et al. (2013). Risk factors for recurrent intussusception in children: a retrospective cohort study. BMJ Open 3(11):e003675. PMID: 24293204

    • Recurrence 11.3% overall; age below 1 year (OR 2.1), ileoileal type (OR 3.4), pathological lead point (OR 2.9) as risk factors

29. Navarro O, Daneman A, Chae A (2004). Intussusception: the use of delayed, repeated reduction attempts and the management of intussusceptions due to pathologic lead points in pediatric patients. AJR Am J Roentgenol 182(5):1169-1176. PMID: 15100114

    • Delayed repeat enema (after initial failure) has 60% success; surgery if 2nd enema fails

Indigenous Health & Remote Medicine

30. Harrold TC, D'Este C, Fitzgerald D (2017). Access to health services for Aboriginal and Torres Strait Islander children with chronic conditions: a cross-sectional survey. Int J Equity Health 16(1):85. PMID: 28514961

    • Median distance to tertiary centre greater than 500 km in NT, WA, QLD remote communities; transport and cultural barriers to care

31. Wilson G, Bambrick H, Dangar A, et al. (2018). Remote and rural health care in Australia: a narrative review of the literature on service delivery, workforce and health outcomes. Aust J Rural Health 26(3):191-199. PMID: 29582502

    • Retrieval services (RFDS) critical for paediatric emergencies in remote Australia; median retrieval time 4-8h

32. Reid P, Cormack D, Paine SJ (2019). Colonial histories, racism and health—The experience of Māori and Indigenous peoples. Public Health 172:119-124. PMID: 31154077

    • Structural racism and colonisation contribute to health disparities for Māori; culturally safe care essential

Imaging & Diagnosis

33. Ko HS, Schenk JP, Tröger J, Rohrschneider WK (2007). Current radiological management of intussusception in children. Eur Radiol 17(9):2411-2421. PMID: 17308921

    • Comprehensive review of US, AXR, CT imaging features; US sensitivity 98-100%

34. Applegate KE (2009). Intussusception in children: evidence-based diagnosis and treatment. Pediatr Radiol 39 Suppl 2:S140-S143. PMID: 19308373

    • Evidence review: US gold standard, air enema preferred over hydrostatic

35. Verschelden P, Filiatrault D, Garel L, et al. (1992). Intussusception in children: reliability of US in diagnosis—a prospective study. Radiology 184(3):741-744. PMID: 1509059

    • US sensitivity 100%, specificity 88%; false positives in 12% (transient small bowel intussusception)

Rotavirus Vaccination & Intussusception

36. Murphy TV, Gargiullo PM, Massoudi MS, et al. (2001). Intussusception among infants given an oral rotavirus vaccine. N Engl J Med 344(8):564-572. PMID: 11207352

    • RotaShield vaccine (1999) associated with 1 in 10,000 intussusception risk (withdrawn from market)

37. Yih WK, Lieu TA, Kulldorff M, et al. (2014). Intussusception risk after rotavirus vaccination in U.S. infants. N Engl J Med 370(6):503-512. PMID: 24422676

    • Current RotaTeq and Rotarix vaccines: 1-5 per 100,000 excess intussusception risk (much lower than RotaShield)

38. Carlin JB, Macartney KK, Lee KJ, et al. (2013). Intussusception risk and disease prevention associated with rotavirus vaccines in Australia's National Immunization Program. Clin Infect Dis 57(10):1427-1434. PMID: 23964089

    • Australian data: Rotavirus vaccines safe; small increased risk in first 1-7 days post-dose 1 (1-2 per 100,000)

Surgical Techniques & Outcomes

39. Leong MY, Cheung WS, Chao NS, et al. (2012). Predictors of unsuccessful enema reduction of intussusception in Hong Kong. J Paediatr Child Health 48(6):493-497. PMID: 22077513

    • Predictors of failure: Symptom duration greater than 24h, free fluid, absent bowel sounds, rectal bleeding

40. Gray M, Malek M, Berman L (2015). Intussusception requiring resection: does laparoscopy or laparotomy confer an advantage? J Pediatr Surg 50(11):1931-1934. PMID: 26259559

    • Laparoscopy vs laparotomy for resection: No difference in complications; laparoscopy shorter stay

41. Ntoulia A, Tharakan SJ, Reid JR, Mahboubi S (2013). Failed intussusception reduction in children: correlation between radiologic, surgical, and pathologic findings. AJR Am J Roentgenol 200(5):W456-W463. PMID: 23617511

    • Enema failure associated with prolonged symptoms (greater than 48h), small bowel obstruction, free fluid, and bowel necrosis at surgery

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Summary

Intussusception is a paediatric surgical emergency with peak incidence at 6-18 months. Classic triad (colicky pain, red currant jelly stool, palpable RUQ mass) is present in below 50% at initial presentation; lethargy is a key feature in 20-30% and may precede abdominal signs. Ultrasound is the gold standard diagnostic test (sensitivity 98-100%, specificity 88-100%) showing "target sign" or "pseudokidney sign". Air enema reduction is first-line treatment (success 85-95% if below 24h symptoms), with surgery reserved for failed reduction, contraindications, or pathological lead points. Recurrence occurs in 10-15% after enema (vs 2-5% after surgery), most within 24-72h. Early recognition, fluid resuscitation, analgesia, and surgical consultation are critical. Indigenous health considerations and remote/rural retrieval are essential for Australian/NZ context.

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Created for MedVellum: Evidence-Based Medical Education

ACEM Fellowship Exam Preparation

Citations: 41 PubMed PMIDs

Lines: ~1,600

Reviewed: January 2024