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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Intussusception classically presents at 6-36 months with episodic severe colicky abdominal pain, drawing legs up, vomiting, and lethargy
- Currant jelly stool is classic but late; do not wait for it
- Ultrasound shows target/doughnut sign and is the diagnostic test of choice
- Stable child without peritonitis: pneumatic or contrast enema is diagnostic and therapeutic
- Peritonitis, perforation, shock, or failed enema requires surgery
Overview
Intussusception occurs when a proximal segment of bowel invaginates into a distal segment, most commonly ileocolic. Lymphoid hyperplasia after viral illness is a common trigger in young children. Older children are more likely to have a pathologic lead point such as Meckel diverticulum, polyp, lymphoma, or IgA vasculitis. The intermittent nature of pain and episodes of lethargy are high-yield exam clues.
Epidemiology
Peak incidence is in infants and toddlers, especially 6-36 months. It is one of the most common abdominal emergencies in this age group. Most cases are idiopathic; pathologic lead points become more likely outside the typical age range, with recurrent episodes, or with small bowel intussusception.
Clinical Features
Symptoms
Sudden episodic severe abdominal pain with crying and knees drawn to chest
Vomiting, initially nonbilious and later bilious if obstruction progresses
Lethargy or altered responsiveness between pain episodes
Bloody mucus currant jelly stool, usually late
Recent viral illness or Henoch-Schonlein purpura symptoms
Signs
Sausage-shaped abdominal mass, often RUQ
Abdominal tenderness or distension
Dehydration or shock in advanced disease
Peritonitis, guarding, or rigid abdomen suggests perforation/ischemia
Empty RLQ Dance sign may be described
Investigations
First-line
Abdominal ultrasoundTest of choice; target/doughnut sign in transverse view and pseudokidney sign longitudinally
Abdominal X-rayAssess obstruction or perforation before enema; may be normal early
Labs if illCBC, electrolytes, lactate, type and screen if shock, perforation, or surgery likely
Second-line
Pneumatic or contrast enemaDiagnostic and therapeutic in stable patients without peritonitis/perforation
CT abdomenRarely needed in typical toddlers; may be used in older children or unclear diagnosis
Specialist
Pediatric radiology and surgeryCoordinate enema reduction with surgical backup
Pediatric surgeryPeritonitis, perforation, failed enema, recurrent pathologic lead point, or unstable child
Management
ACR Appropriateness Criteria for acute abdominal pain and standard US pediatric surgical management1
Initial stabilization
- NPO, IV fluids, analgesia, antiemetics, and correct dehydration
- Assess for peritonitis, shock, and perforation before enema
- Antibiotics if perforation, peritonitis, or surgery anticipated
2
Nonoperative reduction
- Air enema or contrast enema is first-line for stable ileocolic intussusception
- Reduction should occur where surgical backup is available
- Observe after successful reduction for recurrence and oral intake tolerance
3
Surgery
- Immediate surgery for peritonitis, perforation, shock refractory to resuscitation, or failed enema
- Older children or recurrent cases require evaluation for lead point
Complications
- Bowel ischemia and necrosis: Venous congestion and arterial compromise worsen with delayed reduction
- Perforation: Presents with peritonitis/free air and requires surgery
- Recurrence: Can occur after successful enema reduction
- Pathologic lead point: Meckel diverticulum, polyp, lymphoma, or IgA vasculitis, especially in older children
USMLE Step 2 CK Exam Tips
- 1Intermittent colicky pain + knees to chest + lethargy = intussusception
- 2Currant jelly stool is late; absence does not exclude intussusception
- 3Ultrasound target sign is diagnostic
- 4Air enema is both diagnostic and therapeutic in stable patients
- 5Peritonitis or perforation = surgery, not enema
- 6Older child with intussusception = think pathologic lead point
- 7IgA vasculitis can cause intussusception due to bowel wall edema
practicetest your knowledge on intussusceptionApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — pediatrics and beyond.
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