What labs, tests, questions, and physical exam do I perform for a suspected intussusception in a 2-year-old?

Diagnostic Approach to Suspected Intussusception in a 2-Year-Old

For a 2-year-old with suspected intussusception, ultrasound should be the first-line diagnostic imaging modality due to its high sensitivity (97.9%) and specificity (97.8%) for detecting intussusception. 1

Clinical Presentation Assessment

Key History Questions:

• Pattern of abdominal pain (especially intermittent, colicky pain)
• Presence of vomiting (typically non-bilious)
• Stool characteristics (blood in stool, "currant jelly" stools)
• Recent viral illness or respiratory infection
• Duration of symptoms
• Lethargy or altered mental status
• Previous episodes of similar symptoms
• Family history of polyposis syndromes or other GI conditions

Physical Examination Focus:

• Vital signs (assess for fever, tachycardia)
• General appearance (lethargy, irritability)
• Abdominal examination:
  • Palpate for sausage-shaped mass (typically in right upper quadrant)
  • Assess for tenderness, guarding, or peritoneal signs
  • Listen for bowel sounds (may be hyperactive or absent)
• Digital rectal examination:
  • Check for blood or "currant jelly" stool
  • May detect intussusception if advanced to rectum 2
• Assess hydration status

Diagnostic Testing

First-Line Imaging:

• Abdominal ultrasound - most accurate initial test 1
  • Look for characteristic "target" or "pseudokidney" sign
  • Assess for reducibility and identify potential lead points
  • High sensitivity (97.9%) and specificity (97.8%)

Laboratory Tests:

• Complete blood count (CBC) - may show leukocytosis
• Basic metabolic panel - assess for electrolyte abnormalities due to vomiting/dehydration
• Blood type and screen if surgical intervention anticipated

Additional Imaging (if ultrasound is inconclusive):

• Plain abdominal radiographs:
  • Limited utility (sensitivity only 48%, specificity 21%) 1
  • May show signs of obstruction or perforation
  • Should not delay definitive diagnosis or treatment
• CT scan or MRI:
  • Consider if ultrasound is inconclusive and clinical suspicion remains high 3
  • Higher radiation exposure with CT is a concern in children

Diagnostic Pitfalls to Avoid

1. Relying solely on the classic triad - The classic triad of intermittent abdominal pain, currant jelly stool, and palpable sausage-shaped mass is uncommon 4

2. Delaying imaging - Early diagnosis is critical to prevent complications like bowel ischemia, necrosis, and perforation 2

3. Misinterpreting normal radiographs - Abdominal X-rays can be misleading in 20-40% of patients 1

4. Missing atypical presentations - Younger patients may present with altered mental status or lethargy rather than classic abdominal symptoms 4

5. Failing to consider lead points - While most cases in children under 2 years are idiopathic, 10-25% have pathologic lead points 4

Management Considerations

Once diagnosed, prompt reduction is essential:

• Non-operative reduction (hydrostatic or pneumatic) is first-line for stable patients without perforation 5
• Surgical intervention is necessary for unstable patients, those with peritonitis, or when a focal lead point is identified 4

Early diagnosis and management significantly reduces morbidity and mortality and decreases the need for surgical intervention 5.