Telescoping of one bowel segment into another — most common cause of bowel obstruction in children 6 mo to 3 yr.
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Question 1GastrointestinalMedium
An 8-month-old boy is brought in with sudden episodes of inconsolable crying during which he draws his knees to his chest, separated by intervals of calm. He had a viral upper respiratory illness last week. On exam there is a sausage-shaped mass in the right upper quadrant, and his diaper contains stool mixed with blood and mucus. Abdominal ultrasound shows a target sign on transverse imaging, confirming ileocolic intussusception. Which of the following best explains the bloody, mucoid stool?
- ABacterial invasion of the colonic mucosa triggering an inflammatory exudate and bleeding
- BRupture of an arteriovenous malformation within the bowel wall causing brisk hemorrhage
- CVenous compression of the dragged-in mesentery causing congestion and mucosal sloughing
- DAutoimmune deposition of IgA within submucosal vessel walls causing a vasculitic hemorrhage
Reveal answer & full explanation
Correct answer: C — Venous compression of the dragged-in mesentery causing congestion and mucosal sloughing
- ABacterial invasion of the colonic mucosa triggering an inflammatory exudate and bleeding
- BRupture of an arteriovenous malformation within the bowel wall causing brisk hemorrhage
- CVenous compression of the dragged-in mesentery causing congestion and mucosal sloughing✓
- DAutoimmune deposition of IgA within submucosal vessel walls causing a vasculitic hemorrhage
Why Venous compression of the dragged-in mesentery causing congestion and mucosal sloughing is correct
- As the intussusceptum telescopes into the intussuscipiens, the mesentery and its vessels are dragged in and compressed.
- Low-pressure veins collapse first, producing venous congestion, bowel wall edema, and ischemic sloughing of mucosa.
- The shed blood mixed with mucus from the engorged, ischemic bowel is what produces the classic "currant jelly" stool, a late finding seen in roughly 50-60% of cases.
- Untreated, progressive compression leads to arterial compromise, necrosis, and perforation, which is why prompt pneumatic or hydrostatic enema reduction is indicated.
Why the others are wrong
- Bacterial invasion of the colonic mucosa is the mechanism of invasive bacterial colitis (e.g., Shigella, Campylobacter), causing dysentery with fever and fecal leukocytes, not the mechanical venous congestion of intussusception.
- Autoimmune IgA deposition in vessel walls describes Henoch-Schonlein purpura, which can act as a lead point for intussusception but does not itself explain the currant jelly stool here; this child has a postviral idiopathic lead point, not palpable purpura.
- Arteriovenous malformation rupture (angiodysplasia) causes painless lower GI bleeding, typically in older adults, and does not produce the telescoping mass or paroxysmal pain seen here.
Question 2GastrointestinalMedium
An 11-month-old boy is brought to the emergency department after several hours of sudden, episodic screaming during which he draws his knees to his chest, alternating with periods of lethargy. He has passed a stool mixed with blood and mucus. On examination there is a sausage-shaped mass in the right upper quadrant, and abdominal ultrasound shows a target sign that confirms the diagnosis. His parents decline transfer, and reduction is delayed for several hours. Which of the following complications is most likely to develop if the condition remains untreated?
- ABowel ischemia with perforation
- BToxic megacolon with dilation
- CIleal stricture with obstruction
- DShort-bowel syndrome after resection
Reveal answer & full explanation
Correct answer: A — Bowel ischemia with perforation
- ABowel ischemia with perforation✓
- BToxic megacolon with dilation
- CIleal stricture with obstruction
- DShort-bowel syndrome after resection
Why Bowel ischemia with perforation is correct
- In intussusception the proximal bowel telescopes into the distal segment and drags the mesentery with it; mesenteric compression first causes venous congestion, edema, and mucosal sloughing (the source of the currant jelly stool).
- Continued compression then chokes off arterial inflow, producing ischemia. Without timely reduction this advances to bowel necrosis, perforation, and peritonitis or sepsis. This is the central, highest-yield complication and the reason prompt enema or surgical reduction is mandatory.
- Pneumatic (air) enema reduction succeeds in 80-95% of stable cases; surgery is reserved for perforation, peritonitis, failed reduction, or an identified pathologic lead point.
Why the others are wrong
- Toxic megacolon with dilation — a complication of inflammatory bowel disease and infectious colitis (C. difficile and others), driven by transmural inflammation, not by a mechanically telescoping ileocolic segment.
- Short-bowel syndrome after resection — this follows resection of a long segment of necrotic bowel in the operating room, so it presupposes the surgical treatment this child has not yet received rather than being what happens while the intussusception sits untreated.
- Ileal stricture with obstruction — a fibrotic stricture is a late sequela that appears weeks after an ischemic segment has been reduced and has healed, not the acute complication that supervenes over hours of continued mesenteric compression.
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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