Intussusception
Pediatric Surgery
Illness script · Pediatric Surgery
Intussusception
Telescoping of a proximal bowel segment into a distal one, causing obstruction and ischemia; most common in infants 6–36 months.
This illness script for Intussusception covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Peak age: 6–36 months; male > female (3:2)
- Most cases ileocolic (terminal ileum into cecum)
- Idiopathic in ~90% of children (lymphoid hyperplasia/Peyer's patches as lead point)
- Pathologic lead point more common >2 yr: Meckel's diverticulum, polyp, lymphoma
- Post-viral (adenovirus, rotavirus) a common trigger
- Adults: almost always pathologic lead point (malignancy must be excluded)
02
Presentation
- Classic triad: intermittent colicky abdominal pain, vomiting, currant jelly stool (only ~25% have full triad)
- Episodic severe crying with knee-to-chest posture, then appears well between attacks
- Currant jelly stool = bloody mucus; late/ominous sign indicating ischemia
- Palpable sausage-shaped RUQ/epigastric mass (~60%)
- Dance's sign: empty RLQ on palpation (cecum displaced)
- Lethargy/altered mental status can be prominent — mimics encephalopathy
03
Pathophysiology
- Proximal bowel invaginates into distal lumen, dragging mesentery with it
- Venous/lymphatic obstruction → edema → arterial compromise → ischemia/necrosis
- Bowel wall congestion causes mucus mixed with blood ('currant jelly stool') — late sign
- Complete obstruction → perforation if untreated
04
Diagnostics
- Ultrasound is first-line: 'target sign' (donut sign) on transverse view, >2.5 cm — sensitivity >95%
- Plain X-ray: may show paucity of bowel gas RLQ, soft-tissue mass, or obstruction — low sensitivity
- Air-contrast (pneumatic) enema is diagnostic AND therapeutic — gold standard procedure
- CT scan used in adults or equivocal pediatric cases to identify pathologic lead point
- Do NOT attempt enema if peritonitis or perforation suspected — go straight to OR
05
Management
- Stabilize: IV fluids, NPO, NG decompression, IV access
- Pneumatic (air) or hydrostatic (saline/contrast) enema: first-line definitive treatment; ~80–95% success
- Surgical reduction if: enema fails, perforation, peritonitis, or pathologic lead point suspected
- Recurrence rate ~10% after enema reduction; repeat enema acceptable for first recurrence
- Post-reduction observation 12–24 hr; discharge when tolerating feeds and no recurrence
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Meckel's Diverticulum
Also causes painless rectal bleeding in children, but NO palpable mass or colicky intermittent pain; Meckel's scan (Tc-99m pertechnetate) confirms
Volvulus (Midgut)
Bilious vomiting and 'double bubble' / whirlpool sign on imaging; peak in neonates <1 month, not 6–36 month range
Gastroenteritis
Diarrhea is watery/non-bloody early; pain is constant rather than episodic; NO palpable abdominal mass or target sign on US
Incarcerated Inguinal Hernia
Tender groin mass; bowel obstruction but no RUQ sausage mass; ultrasound shows hernia not target sign
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Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.