Intussusception in children

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Intussusception in Children

Definition and Mechanism

Intussusception is the telescoping (invagination) of a proximal segment of bowel (the intussusceptum) into a more distal segment (the intussuscipiens), driven by peristaltic force acting on a lead point. This causes mechanical bowel obstruction, followed by venous congestion, bowel wall edema, ischemia, and - if untreated - gangrene and perforation.

Diagram showing lead point, intussusceptum, intussuscipiens, apex and neck

Schematic: the lead point drives the intussusceptum into the intussuscipiens. The apex is the most distal point; the neck is the entry point.

Epidemiology

Most common cause of intestinal obstruction in children under 2 years; second most common pediatric acute abdomen after appendicitis
Peak incidence: 5-12 months of age (most series say 5-9 months)
50% occur under age 1; <25% occur after age 2
Male predominance (approximately 3:2)

Types

Type	Frequency	Notes
Ileocolic	>80%	Most common; ileum telescopes through ileocecal valve into colon
Ileoileocolic	Uncommon
Ileo-ileal	Rare	More likely in HSP; not amenable to enema reduction
Colocolic	Rare

Etiology and Lead Points

Idiopathic (>90% in young children): Caused by hypertrophy of Peyer's patches - typically following a viral infection (gastroenteritis, upper respiratory infection). The rotavirus vaccine has also been implicated in triggering lymphoid swelling.

Pathologic lead points (5-12%): More common in children >5-6 years old and in recurrences. Causes include:

Meckel's diverticulum (most common pathologic lead point)
Intestinal polyps
Intestinal duplication cyst
Submucosal hemorrhage from Henoch-Schönlein Purpura (HSP)
Lymphoma
Appendiceal inflammation
Foreign body
Ectopic gastric/pancreatic tissue
Nasojejunal tubes (iatrogenic)
Cystic fibrosis, celiac disease, postsurgical adhesions

Clinical Presentation

The classic triad - present together in only a minority of patients:

Colicky abdominal pain - the most consistent symptom. Episodic, severe, lasting 10-15 minutes with 15-30 minute pain-free intervals; child draws legs up, is inconsolable during attacks, appears well between episodes
"Currant jelly" stool - bloody mucus stool; a late finding, seen in <50%; indicates bowel ischemia
Palpable sausage-shaped abdominal mass - in the right upper/mid abdomen; present in <50%

Other features:

Vomiting (common, initially non-bilious)
Dehydration
Lethargy or altered consciousness - an important atypical presentation; can mimic neurologic emergencies
Pallor
Progressive abdominal distension
Signs of shock if presentation is delayed

Differential Diagnosis

Condition	Distinguishing features
Appendicitis	Fever, RLQ tenderness, WBC rise, gradual onset
Volvulus	Bilious vomiting, more sudden, neonates
Meckel diverticulitis	Painless rectal bleeding typical
Gastroenteritis	No obstruction pattern, diarrhea predominates
HSP	Rash, arthritis, hematuria
Incarcerated hernia	Groin/scrotal mass
Testicular/ovarian torsion	Sudden severe pain, groin/pelvic location

Imaging and Diagnosis

Ultrasound (modality of choice)

Sensitivity and specificity approaching 100% in trained hands. Key findings:

Target sign / Bull's eye / Doughnut sign - transverse view shows concentric rings of bowel wall (3-5 cm mass)
Pseudokidney sign / Sandwich sign - longitudinal view showing the intussusceptum protruding into the colon
Crescent-in-doughnut sign - hyperechoic crescentic mesenteric fat pulled into the intussusceptum
Lymph nodes and fluid may be visible within the mass
Look for secondary lead points and free fluid

Ultrasound target sign (A, transverse) and pseudokidney sign (B, longitudinal) of ileocolic intussusception in the RLQ

(A) Transverse view: the classic "target sign" - multilayered concentric ring appearance. (B) Longitudinal (sagittal) view: the "pseudokidney sign."

Plain Abdominal Radiograph

Not routinely recommended as a first-line test, but may show:

Meniscus sign - soft tissue mass contrasting against air-filled bowel
Paucity of gas in RIF (cecum may be absent from its usual location)
Dilated proximal small bowel loops (obstruction)
Free intraperitoneal air (perforation - rare but important to exclude before reduction)

Plain abdominal X-ray showing soft tissue density in RUQ with obscured liver edge and dilated bowel - intussusception

Abdominal X-ray: arrows point to the soft tissue shadow of the intussusceptum producing a meniscus appearance.

Management

Initial Resuscitation

IV access and fluid boluses (20 mL/kg normal saline) until hemodynamically stable
NPO, nasogastric tube if vomiting/distended
Broad-spectrum antibiotics (given risk of ischemic bowel)
Prompt surgical consultation before any reduction attempt

Non-Operative Reduction (First-line)

Pneumatic (air) enema is preferred at most centers:

Air is insufflated under fluoroscopic guidance
Confirms reduction when air flows freely into terminal ileum
Overall success rate 80-90% for ileocolic intussusception
Faster, no radiation from contrast, equally efficacious compared to barium/water-soluble enema

Hydrostatic (contrast) enema:

Barium or water-soluble contrast under fluoroscopic control
Equivalent success rates

Contraindications to non-operative reduction:

Free intraperitoneal air (perforation)
Clinical peritonitis
Hemodynamic instability / shock
Entirely small bowel intussusception (not amenable to enema)

Complications: Colonic perforation (rare but can cause tension pneumoperitoneum if air enema).

Operative Management

Indicated when:

Non-operative reduction fails
Peritonitis or perforation present
Hemodynamic instability
Multiple recurrences (third recurrence)
Known/suspected pathologic lead point

Technique: Open or laparoscopic. Retrograde squeezing (pushing, not pulling) of the intussusceptum proximally. Bowel viability is assessed after reduction. If non-viable bowel or pathologic lead point: resection + primary anastomosis. The lymphoid tissue at the ileocecal valve may be deliberately excised (incidental appendectomy also done by many surgeons).

Intraoperative view of ileocolic intussusception being manually reduced

Intraoperative photograph of ileocolic intussusception showing the characteristic appearance during surgical reduction.

Recurrence

After non-operative reduction: ~5-11% recurrence rate, usually within 24-48 hours
Most recurrences are managed with repeat enema
A third recurrence is an indication for operative management (to exclude a pathologic lead point and prevent future episodes)
Observation for 6 hours post-reduction is appropriate; if tolerating oral fluids, discharge is safe

Disposition

Brief observation (6 hours) after successful non-operative reduction
Children tolerating oral intake can be discharged home
Fever is common after reduction and typically resolves without specific treatment
Return precautions for recurrence symptoms

Key Points Summary

Feature	Detail
Age	Peak 5-12 months; most under 2 years
Most common type	Ileocolic (>80%)
Most common lead point in >2yr	Meckel's diverticulum
Pathognomonic stool	"Currant jelly" (late, <50%)
Imaging of choice	Ultrasound (sensitivity/specificity ~100%)
Treatment of choice	Pneumatic (air) enema reduction
Success rate	80-90%
Recurrence	~5-11%; repeat enema usually effective
Surgery indication	Failed reduction, peritonitis, perforation, shock

Sources: Rosen's Emergency Medicine (9th ed.) - Ch. 166; Bailey and Love's Surgery (28th ed.) - Ch. 17; Sabiston Textbook of Surgery; Grainger & Allison's Diagnostic Radiology - Ch. 71; Fischer's Mastery of Surgery (8th ed.)

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