What are the clinical features and diagnosis of intussusception?

Clinical Features and Diagnosis of Intussusception

Clinical Presentation

Intussusception classically presents with intermittent, colicky abdominal pain manifesting as sudden episodes of intense crying with the infant drawing their knees to the chest, followed by periods of relative calm between episodes. 1

Key Clinical Features by Frequency

• Abdominal pain (intermittent, crampy): The most distinctive feature, occurring in approximately 72% of cases 2. The pain is episodic in nature, with the child appearing relatively normal between episodes 3, 1

• Vomiting: Present in 84% of pediatric cases 4. Initially nonbilious, but may become bilious as obstruction progresses later in the disease course 1, 5

• Bloody stools ("currant jelly" stools): A late finding that develops as the condition progresses 3, 1, 5. Gross blood or guaiac-positive stools are common but not always present initially 5

• Palpable abdominal mass ("sausage-shaped"): Found in only 56% of cases 4

• Lethargy or altered mental status: Particularly important in younger infants who may present atypically 5, 6. This can be a primary presenting sign rather than a late finding 5

Critical Clinical Pitfall

The classic triad of abdominal pain, bloody stools, and palpable mass occurs together in only 7.5% of patients 4. Therefore, a high index of suspicion is essential when any individual feature is present, particularly in infants aged 3 months to 5 years 3, 1, 5.

Age-Specific Considerations

• Peak incidence: 3 months to 5 years of age, with most cases occurring between 5-9 months 3, 5, 6

• Unusual before 3 months of life: Intussusception is uncommon in the first 3 months 3

• Etiology varies by age: Most cases in the typical age range (5-9 months) are idiopathic, while 10-25% have an identifiable pathologic lead point (Meckel's diverticulum, polyps, masses) 5, 6. Neonates, older children, and adults more commonly have lead points 6

Diagnostic Approach

Ultrasound is the diagnostic modality of choice for intussusception 1, 5, 6.

Imaging Modalities

• Ultrasound (first-line):

  • Demonstrates the classic "target sign" or "doughnut sign" on transverse view 4
  • Sensitivity of 98.1% for detecting the characteristic target lesion 4
  • Proven highly useful in the pediatric age group for evaluating intussusception 3
  • Low-risk, accurate screening tool when performed by experienced ultrasonographers 6

• Plain abdominal radiographs (supplementary):

  • May show dilated small-bowel loops with air-fluid levels and paucity of colonic gas 3
  • Useful for evaluating for complications such as obstruction or perforation 5
  • Not definitive in many cases and may prolong evaluation 3

• CT scan (adults or complicated cases):

  • Provides more comprehensive information about the entire gastrointestinal tract, 3-D anatomy, and underlying causes 3
  • Preferred by surgeons for adult patient management 3
  • Recommended for hemodynamically stable adults to confirm diagnosis and identify complications 7

Physical Examination Essentials

• Rectal examination with occult blood testing: An important part of the evaluation and frequently positive 6

• Assessment for peritonitis or bowel compromise: Look for signs of strangulation, ischemia, or perforation requiring immediate surgery 7

• Evaluation of hemodynamic stability: Critical for determining intervention urgency 7

• Neurologic assessment: Particularly in younger infants who may present with lethargy or altered mental status as the primary complaint 5

Clinical Algorithm for Diagnosis

1. Maintain high suspicion in any infant 3 months to 5 years presenting with intermittent abdominal pain, vomiting, or unexplained lethargy 3, 1, 5

2. Perform focused physical examination including abdominal palpation for mass and rectal examination with occult blood testing 6

3. Obtain ultrasound immediately as the primary diagnostic test 1, 5, 6

4. Consider plain radiographs if perforation or complete obstruction is suspected 5

5. Assess for complications requiring immediate surgical intervention (peritonitis, hemodynamic instability, signs of bowel necrosis) 7

Important Caveats

• Do not wait for the complete triad: Only 7.5% of patients present with all three classic features together 4. Diagnosis must be considered with any single feature in the appropriate age group 5, 4

• Atypical presentations are common: Lethargy or altered mental status may be the primary presenting sign, especially in younger infants 5, 6

• Time-sensitive diagnosis: If intussusception remains untreated, progression to obstruction, ischemia, necrosis, and perforation occurs 5. The 48-hour threshold is critical, as mortality increases significantly with delayed intervention 7

• Adult cases differ significantly: 86-93% of adult intussusception cases have an underlying pathologic lesion (malignancy, inflammatory bowel disease, adhesions), and approximately 20% may be asymptomatic, discovered incidentally on imaging 7, 2