Telescoping of one bowel segment into another — most common cause of bowel obstruction in children 6 mo to 3 yr.
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Risk factors
- Recent viral illness (often adenovirus, rotavirus) — lymphoid hyperplasia of Peyer patches as lead point
- Meckel diverticulum, polyps, intestinal duplication (more common as lead points in older children >2 yr)
- Henoch-Schönlein purpura (small bowel intussusception with intramural hematoma as lead point)
- Cystic fibrosis, celiac disease (older children)
- Lymphoma, neuroblastoma (older children, adults)
Pathophysiology
A lead point or lymphoid tissue is dragged forward by peristalsis, pulling proximal bowel into distal bowel. The mesentery is compressed, causing venous congestion, edema, and mucosal sloughing (producing the classic 'currant jelly' stool of blood and mucus). Without reduction, progressive ischemia leads to necrosis, perforation, and peritonitis.
Clinical presentation
Symptoms
- Sudden, episodic, severe abdominal pain — child draws knees to chest, screams, then becomes calm between episodes
- Vomiting, initially nonbilious then bilious if obstruction progresses
- 'Currant jelly' stools (late finding, ~50-60%) — mixed blood and mucus
- Lethargy and altered mental status can be a striking and sometimes sole presentation
Signs / physical exam
- Sausage-shaped mass in the right upper quadrant (palpable in ~60%)
- Dance sign: empty right lower quadrant (cecum displaced superiorly)
- Abdominal distention, peritoneal signs if perforated
- Tachycardia, dehydration
Classic findings
Intermittent inconsolable crying with knees drawn up in a 6-12 month old, with or without currant jelly stool, is intussusception until proven otherwise.
Differential diagnosis
- Gastroenteritis — Diffuse vomiting and diarrhea without paroxysmal abdominal pain or palpable mass
- Malrotation with volvulus — Bilious emesis in infant <1 month is volvulus until proven otherwise; upper GI series is the test of choice
- Incarcerated hernia — Groin or umbilical bulge; clinical exam
- Meckel diverticulitis — Painless lower GI bleeding more common than obstruction; technetium scan
- Appendicitis (older child) — RLQ pain, fever, peritoneal signs; usually >5 yr
- Pyloric stenosis (younger infant) — Nonbilious projectile vomiting at 3-6 weeks; palpable olive; ultrasound diagnostic
- Constipation — Hard stool palpable, no paroxysmal pain or currant jelly stool
Diagnostic workup
Diagnostic criteria
Ultrasound demonstration of target or pseudokidney sign establishes the diagnosis.
Labs
- CBC, BMP, lactate, type and screen
- Stool guaiac if rectal exam performed
Imaging
- Abdominal ultrasound — first-line; 'target' or 'donut' sign on transverse view, 'pseudokidney' on longitudinal view; sensitivity and specificity ~98%
- Abdominal radiograph — may show paucity of gas in RLQ, soft tissue mass; nondiagnostic alone but excludes free air
- Contrast (air or water-soluble) enema — both diagnostic and therapeutic
Treatment
First-line
- IV access, fluid resuscitation, NPO, NG decompression if vomiting
- Surgical consultation prior to attempted reduction
- Pneumatic (air) enema reduction under fluoroscopy — first-line, success rate 80-95%
- Hydrostatic (saline or water-soluble contrast) enema reduction is an acceptable alternative
- Broad-spectrum antibiotics (e.g., piperacillin-tazobactam or ampicillin-sulbactam) if signs of ischemia or before surgery
Complications
- Bowel ischemia, necrosis, and perforation
- Peritonitis and sepsis
- Short bowel syndrome after extensive resection
- Recurrent intussusception (~10%)
- Death (rare with prompt treatment, high if untreated)
PANCE pearls
- Always consider intussusception in a previously well child <2 years with intermittent, severe abdominal pain — the absence of currant jelly stool does not rule it out.
- Lethargy out of proportion to physical findings can be the only presenting feature.
- Ultrasound has replaced contrast enema for diagnosis; enema is reserved for therapeutic reduction.
- Pathologic lead points (Meckel, polyp, lymphoma) are uncommon under age 2 but common over age 5 — investigate accordingly.
- Rotavirus vaccine has a very small absolute increased risk of intussusception (~1-5 per 100,000); benefit far outweighs risk.
References
- AAP 2017 — AAP clinical practice guidance on the evaluation and management of pediatric intussusception
- ESPGHAN 2019 — European Society for Paediatric Gastroenterology Hepatology and Nutrition position paper on intussusception
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