Intussusception

Overview and definitions

Intussusception is telescoping of a proximal intestinal segment (intussusceptum) into an adjacent distal segment (intussuscipiens), producing bowel obstruction, venous and lymphatic congestion, ischemia, and possible necrosis.

Classified by location:

• Ileocolic (terminal ileum into colon) — most common (~90% of pediatric cases)
• Ileoileocolic (ileum into colon with additional ileal component)
• Small‑bowel (jejunojejunal, ileoileal)
• Colocolic (colon into colon)

Etiology: mostly idiopathic in young infants; pathologic lead points (Meckel diverticulum, polyps, lymphoma, duplication cysts, etc.) are more likely in older children and adults.

Epidemiology

• Peak incidence: 4–14 months of age (most cases idiopathic).
• Male predominance (mild).
• Small‑bowel and colonic intussusceptions are less common in children; lead points occur in ~5% of typical infant ileocolic cases but more often in older children.
• Transient increases in incidence historically followed the withdrawn Rotashield® vaccine; current rotavirus vaccines have not been clearly associated with an increased population risk that outweighs benefits.

Pathophysiology

Hypertrophy of Peyer patches/lymphoid tissue (postviral) often initiates ileocolic intussusception in infants. Invagination drags mesentery, compresses venous outflow → edema and progression to arterial compromise if unresolved. Prolonged ischemia → mucosal sloughing, bleeding (“currant‑jelly” stool), perforation, peritonitis, systemic sepsis.

Common pathologic lead points

• Meckel diverticulum
• Polyps (juvenile polyps)
• Duplication cyst
• Lymphoma
• Massive lymphoid hyperplasia
• Henoch‑Schönlein purpura
• Cystic fibrosis
• Appendicitis/periappendicitis

Clinical presentation

• Classic triad (colicky abdominal pain, currant‑jelly stools, abdominal mass) in <50%.
• Maintain high index of suspicion with symptoms of intestinal obstruction: colicky abdominal pain, often with bilious vomiting. Between bouts of colic, infants are quiet but irritable.
• May palpate characteristic soft sausage‑shaped abdominal mass — meniscus sign.
• Diarrhea occurs in ~10% prior to mucosal slough.
• Hypovolemia is variable; some children present atypically with lethargy only.
• Passage of blood and mucus per rectum is a late sign of intussusception.

Differential diagnosis

• Acute gastroenteritis
• Colic
• Appendicitis (older child)
• Malrotation/volvulus
• Bowel obstruction from atresia or adhesions
• Intussusception secondary to lead point (Meckel diverticulum, polyp)
• Henoch‑Schönlein purpura
• Sepsis with ileus

Diagnosis — practical approach

1. Initial stabilization: NPO, IV access, fluid resuscitation, pain control, nasogastric tube if vomiting, monitor vitals and perfusion.
2. Plain abdominal radiograph: useful to exclude perforation (free air) or other causes; frequently nonspecific in intussusception. Classic meniscus sign or soft tissue mass seen in ~25%.
3. Ultrasound (first‑line diagnostic test when available):
   • Transverse view: concentric rings / “doughnut” or “target” sign.
   • Longitudinal view: “pseudokidney” or “sandwich” sign.
   • Sensitivity and specificity approach ≈100% in experienced hands; can identify lead points, estimate bowel viability (wall thickness, Doppler perfusion), and confirm reduction if repeated after therapy.
4. Contrast enema (air or liquid) under fluoroscopic or ultrasound guidance: diagnostic and therapeutic; contraindicated if perforation suspected or patient hemodynamically unstable.
5. CT scan: highly sensitive but usually avoided in children due to radiation; used in atypical/older patients or unclear ultrasound findings.
6. Endoscopy: rarely used diagnostically; can be therapeutic in colocolic intussusception during colonoscopy in specialized situations.

Nonoperative (radiologic) reduction — principles and technique

• Two main methods: pneumatic (air) enema and hydrostatic (saline or contrast) enema.
• Indications: hemodynamically stable child without signs of perforation or peritonitis.
• Contraindications: clinical perforation/peritonitis, free intraperitoneal air on radiograph, unstable shock despite resuscitation.
• Pneumatic (air) enema advantages: shorter procedure time, less radiation (if fluoroscopy optimized), high success rates; many centers prefer air for ileocolic intussusception.
• Hydrostatic (saline) enema under ultrasound guidance avoids radiation and is effective; saline is increasingly the liquid of choice when doing hydrostatic reductions.
• Success rates: typically 75%–90% for first attempt (higher for early presentations and ileocolic cases). Success depends on duration of symptoms, presence of lead point, small‑bowel location, and bowel ischemia.
• Technique essentials: experienced radiology team, controlled pressure gradients (monitor height/pressure), continuous monitoring of patient, swift termination with signs of perforation or instability.
• Complications: bowel perforation (~1% across techniques), tension pneumoperitoneum after air enema (rare), recurrence (early recurrence within 48 hours relatively low but possible).
• After successful reduction: observe for several hours, confirm passage of stool, ensure stable vitals and feeding tolerance before discharge in typical uncomplicated infants; schedule follow‑up and counsel caregivers about recurrence signs.

Recurrence and failure

• Recurrence rate after successful enema reduction: variable, commonly 5%–10%; most recurrences occur early (within 48 hours) but can occur later.
• Predictors of failed enema reduction: symptom duration >24–48 hours, presence of pathologic lead point, small‑bowel (jejunojejunal/ileoileal) intussusception, signs of perforation, multiple recurrences, or evidence of bowel compromise.

Surgical management

• Indications for surgery: failed nonoperative reduction, peritonitis, perforation, hemodynamic instability, or suspicion of pathologic lead point requiring resection.
• Operative options: manual reduction (attempt gentle reduction), segmental resection with primary anastomosis when bowel necrosis or irreducible lead point present, and appendectomy if indicated.
• Laparoscopic reduction is possible in selected stable patients and centers with expertise.
• Intraoperative considerations: inspect for Meckel diverticulum, polyps, duplication cyst, lymphoma; resect only nonviable or pathologic bowel; avoid excessive force during attempted reduction to minimize risk of tear or perforation.

Special situations

• Infants <3 months: atypical presentation, higher risk of pathological lead point and perforation; lower success rates for enema; maintain high suspicion.
• Older children and adults: greater likelihood of pathological lead point (e.g., tumor); CT imaging more frequently used; operative management more common.
• Small‑bowel intussusception: frequently transient and self‑resolving if short; persistent symptomatic small‑bowel intussusception or one with lead point requires intervention.

Complications and prognosis

• Early complications: bowel ischemia and necrosis, perforation, peritonitis, sepsis, shock.
• Late complications: adhesive small‑bowel obstruction after surgery, short bowel when extensive resection required, recurrent intussusception.
• Prognosis: excellent with prompt diagnosis and reduction for typical ileocolic cases; morbidity and mortality increase with delayed diagnosis, bowel necrosis, perforation, or when lead points (e.g., malignancy) are present.

Prevention and public health notes

No specific primary prevention for idiopathic intussusception. Recognition of vaccine associations has led to surveillance; modern rotavirus vaccines carry a small attributable risk in some studies but confer major benefits and remain recommended in most settings. Educate caregivers on signs of recurrence after discharge (recurrent severe abdominal pain, vomiting, lethargy, bloody stools).

High‑yield clinical pearls (board and clinical)

• Suspect intussusception in any infant/toddler with intermittent severe abdominal pain and vomiting — evaluate urgently.
• Ultrasound is the diagnostic modality of choice in children (doughnut/target on transverse; pseudokidney on longitudinal).
• Contrast/air enema is both diagnostic and therapeutic; pneumatic and hydrostatic techniques have similar efficacy when performed by experienced teams.
• Avoid enemas when perforation/peritonitis suspected; stabilize hemodynamically first.
• Older children or atypical presentations are more likely to have a pathologic lead point; imaging and surgical consultation should be expedited.

Quick reference table — distinguishing features