Intussusception

Intussusception – High-Yield Study Guide for Medical Students

Definition

Intussusception is the invagination (telescoping) of a proximal segment of the intestine (intussusceptum) into an adjacent distal segment (intussuscipiens), leading to bowel obstruction, venous congestion, ischemia, and potential bowel necrosis if not promptly treated.^[1]

Epidemiology

Intussusception is the most common cause of intestinal obstruction in infants and young children.

• Age: Peak incidence between 6–36 months; rare in neonates, less common after 3 years.^[1]
• Sex: Male predominance (≈2:1).
• Location: Most commonly ileocolic (terminal ileum into cecum).
• Etiology:
  • Idiopathic in most children (thought to be related to hypertrophied Peyer patches after viral infection, e.g., adenovirus).
  • Lead point–associated intussusception is more common in older children and adults (e.g., Meckel diverticulum, intestinal polyp, lymphoma, Henoch–Schönlein purpura, duplication cyst).^[2]
• Adults: Rare; usually has a structural lead point (e.g., benign or malignant tumor).

Pathophysiology

The pathophysiology of intussusception is driven by abnormal peristalsis and the presence of a leading focus:

• A segment of bowel is drawn into a distal segment along the axis of peristalsis, usually at the ileocecal junction.
• Mesentery of the proximal segment is dragged along, causing compression of mesenteric veins and lymphatics first, with continued arterial inflow.
• This leads to venous congestion, edema, and increased intraluminal pressure.
• Progressive swelling compromises arterial blood flow, resulting in ischemia, mucosal sloughing, bleeding, and potential transmural necrosis and perforation if untreated.^[1]
• Sloughed mucosa and blood mix with mucus to form “red currant jelly” stool, a late and specific but not very sensitive sign.

Clinical Presentation

Presentation varies with age and duration. Early recognition is critical to prevent ischemia and perforation.

Classic Pediatric Features

• Triad (seen in minority of cases, ~15–30%):
  • Intermittent, severe, colicky abdominal pain – sudden onset, episodes every 15–20 minutes, with normal behavior between episodes.
  • Vomiting – initially non-bilious, may become bilious with prolonged obstruction.
  • “Red currant jelly” stools – blood and mucus in stool, typically late finding.^[2]
• Other common findings:
  • Lethargy, pallor; sometimes lethargy can be the dominant early symptom.
  • Refusal to feed, irritability.
  • Abdominal distension (often later) and decreased stooling.
  • Sausage-shaped, palpable mass usually in the right upper quadrant or epigastrium. The right lower quadrant may feel empty – the Dance sign.^[1]
• Systemic signs (late): fever, tachycardia, hypotension, signs of peritonitis, suggesting perforation or sepsis.

Adult Presentation

• Often chronic or intermittent abdominal pain.
• Nausea, vomiting, altered bowel habits, occasionally GI bleeding.
• Frequently associated with a pathologic lead point (benign or malignant lesion).

Diagnosis

Diagnosis is based on clinical suspicion and confirmed with imaging. Early imaging is crucial for timely, non-operative reduction.

Initial Evaluation

• History and physical exam focusing on abdominal pain characteristics, vomiting, stool changes, and systemic signs.
• Assess hemodynamic status and look for signs of peritonitis (rigidity, guarding, rebound).
• Basic labs may include CBC, electrolytes, type and screen; they support overall assessment but are not diagnostic.

Imaging

• Ultrasound (US) – first-line imaging in children.
  • Highly sensitive and specific when performed by experienced sonographers.
  • Classic US signs:
    • “Target” or “doughnut” sign in transverse view – concentric hypoechoic and hyperechoic rings representing bowel within bowel.^[1]
    • “Pseudokidney” or “sandwich” sign in longitudinal view.
  • Can assess bowel perfusion using color Doppler (helpful for ischemia assessment).
• Abdominal radiograph
  • Non-specific; may show signs of bowel obstruction.
  • Used mainly to look for free intraperitoneal air (perforation) or high-grade obstruction before enema reduction.
• Contrast enema (air or liquid contrast)
  • In children, serves both diagnostic and therapeutic purposes.
  • Shows a filling defect with a characteristic coiled spring or meniscus appearance.
  • Performed under fluoroscopic or ultrasound guidance by experienced radiology and pediatric surgery teams.^[3]
• CT scan
  • More often used in adults or equivocal pediatric cases.
  • Shows a “target” or “sausage-shaped” mass with layers of bowel and mesenteric fat.

Management

Management aims to stabilize the patient, reduce the intussusception, and address any underlying lead point. Timely intervention is crucial to prevent ischemia, necrosis, and perforation.

Initial Stabilization

• Airway, breathing, circulation (ABCs) – prioritize hemodynamic stability.
• IV access, fluid resuscitation with isotonic crystalloids as indicated.
• NPO (nothing by mouth) and NG tube decompression if significant distension or vomiting.
• Pain control and monitoring of vital signs.
Broad-spectrum antibiotics if there are signs of systemic toxicity, peritonitis, or concern for ischemia/perforation.

Definitive Treatment in Children

• Non-operative reduction (preferred if no signs of perforation or peritonitis):
  • Pneumatic (air) enema reduction or hydrostatic enema with contrast (barium or water-soluble) or saline under fluoroscopic or ultrasound guidance.
  • Success rates are high (≈80–90% in appropriate candidates).^[3]
  • Contraindications include suspicion of perforation, severe peritonitis, or profound shock not yet stabilized.
• Surgical management:
  • Indicated when:
    • Enema reduction is unsuccessful or not available.
    • There is evidence of perforation or peritonitis.
    • A lead point is strongly suspected (older child, recurrent intussusception, atypical location).
  • Laparotomy or laparoscopy with gentle manual reduction of the intussusception.
  • Resection of nonviable bowel and removal of an identifiable lead point.

Adult Intussusception Management

• Greater likelihood of an underlying pathologic lead point, often neoplastic.
• Management typically involves surgical resection of the involved segment rather than enema reduction, especially in colonic lesions, due to malignancy risk.
• Preoperative imaging helps define extent and likely etiology.

Post-Reduction Care

• Observe for several hours after enema reduction for recurrence, persistent pain, or perforation.
• Gradual reintroduction of oral intake as tolerated.
• Parents/caregivers should be educated on signs of recurrence.
• Recurrence rate after successful enema reduction: approximately 5–10%.^[3]

Complications

• Bowel ischemia and necrosis due to prolonged vascular compromise.
• Perforation, either from disease progression or during enema/surgical reduction.
• Peritonitis and sepsis.
• Short bowel syndrome if extensive resection is required.
• Recurrence of intussusception.

Prognosis

• With early diagnosis and appropriate management, prognosis in children is excellent.
• Delay in treatment increases risk of ischemia, necrosis, perforation, and mortality.
• Prognosis in adults depends heavily on the underlying cause (e.g., malignancy).

Key Clinical Pearls (High-Yield for Exams)

• Most common cause of intestinal obstruction in infants and toddlers, especially 6–36 months.
• Classical triad – intermittent colicky pain, vomiting, red currant jelly stool – is high-yield but present in a minority; absence does not exclude diagnosis.
• Look for a sausage-shaped mass in RUQ and an empty RLQ (Dance sign).
• Ultrasound is the diagnostic test of choice in children (target sign).
• Air or contrast enema is both diagnostic and therapeutic; contraindicated if perforation or peritonitis is suspected.
• In older children and adults, always think of an underlying pathologic lead point (e.g., Meckel diverticulum, tumor).
• Lethargy can be the predominant symptom in infants and should not be misinterpreted as primarily neurologic or septic without considering abdominal pathology.
• Recurrence after non-operative reduction is possible; ensure appropriate follow-up and caregiver education.

Exam Tip Summary

• USMLE-style stem: 1-year-old with intermittent crying, draws up legs, vomiting, currant jelly stool, RUQ mass – think intussusception.
• Best next diagnostic step in a stable child: Ultrasound.
• Best therapeutic step if no perforation/peritonitis: air enema reduction.
• Adults with intussusception usually need segmental resection due to high malignancy association.

References

• 1. Blakelock RT, Beasley SW. (2017). Intussusception in children. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. Available at: https://www.ncbi.nlm.nih.gov/books/NBK431078/
• 2. UpToDate. Intussusception in children: Clinical features and diagnosis. Available at: https://www.uptodate.com/contents/intussusception-in-children-clinical-features-and-diagnosis
• 3. UpToDate. Intussusception in children: Management. Available at: https://www.uptodate.com/contents/intussusception-in-children-management