Intussusception

Epidemiology

• Most common cause of intestinal obstruction in infants and young children (second only to appendicitis as a cause of acute abdomen in pediatric patients)
• Peak incidence: 5-9 months; nearly all cases occur under 2 years of age, though it can occur up to school age
• In adults: rare, accounting for only ~1% of all intestinal obstruction cases

Types

Pathophysiology & Lead Points

• Meckel's diverticulum
• Intestinal polyp
• Duplication cyst
• Small bowel lymphoma
• Nasojejunal tubes
• Malignancy (adults - the dominant cause)

Key clinical rule: In adults, symptomatic intussusception is associated with a pathologic - often malignant - process in 80-90% of cases, mandating surgical exploration WITHOUT enema reduction attempts.

• Infants <3 months or children >6-7 years
• Recurrent intussusception

Clinical Features

Classic Triad (less than 25% present with all three)

1. Colicky abdominal pain - episodic, paroxysmal; the child draws up their legs and screams, then appears well between episodes
2. "Currant jelly" / "redcurrant jelly" stools - blood and mucus mixed, from ischemic mucosal sloughing of the intussusceptum
3. Palpable abdominal mass - sausage-shaped mass in the right upper quadrant / right side of abdomen (present in <50%)

Other Features

• Vomiting (early and bilious if obstruction develops)
• Lethargy/pallor
• Signs of dehydration and hypovolemia as disease progresses
• "Dance's sign": empty right iliac fossa due to displacement of caecum

The situation can deteriorate rapidly in infants - hypovolemia and shock can develop quickly. Prolonged symptom duration reduces the likelihood of successful non-operative reduction.

Investigations

Ultrasound - First Line (sensitivity & specificity ~100%)

• Transverse plane: "target sign" or "doughnut sign" - a mass 3-5 cm in diameter with concentric rings
• Longitudinal plane: "sandwich sign"
• "Crescent in doughnut" sign: hyperechoic semilunar structure = mesenteric fat pulled into the intussusceptum - distinguishes from mimickers
• Lymph nodes and free fluid may be seen within the intussusceptum
• Use a high-frequency linear array transducer; mass is usually found just deep to the anterior abdominal wall, right of midline

Plain Radiograph (controversial; not routinely recommended)

• Soft-tissue mass contrasting an air-filled bowel loop ("meniscus sign")
• Proximal dilated gas-filled bowel loops
• Absence of gas in the caecum (suggests ileocaecal intussusception)
• Free intraperitoneal gas is extremely rare but would contraindicate enema reduction

CT Scan (adults / uncertain cases)

Management

Initial Resuscitation (all patients)

• IV fluid resuscitation
• Nasogastric decompression
• Broad-spectrum antibiotics
• Analgesia

Non-operative Reduction (children - first-line)

• Peritonitis (clinical signs)
• Free intraperitoneal air on imaging
• Hemodynamic instability / shock

• Target reduction rate: >80%
• Success is confirmed when air/contrast flows freely into small bowel AND symptoms resolve
• Sedation has been shown to increase success rate without increase in complications
• Recurrence rate: ~5% after successful non-operative reduction

Surgical Management (open or laparoscopic)

• Failed non-operative reduction (>2-3 attempts)
• Perforation or peritonitis
• Clinical deterioration
• Suspected pathological lead point
• Adult intussusception (virtually always)
• Small bowel intussusception (not suited for enema)
• Strangulation / bowel infarction

• Manual reduction: squeeze the intussusceptum back through the intussuscipiens (do NOT pull from the proximal end)
• Resection and anastomosis: if reduction fails, bowel is non-viable, or a pathological lead point is present
• In adults: primary resection without attempted intraoperative reduction is the preferred approach for colonic/ileocolic intussusception, given the high malignancy rate

Adult Intussusception - Special Considerations

• Accounts for <5% of all intussusception cases
• Presents subacutely - symptoms may persist days to weeks
• Often found incidentally at CT or at surgery
• 80-90% have a pathological lead point, most commonly malignant (colonic adenocarcinoma, metastases, lymphoma)
• No attempt at enema reduction - proceed to surgical resection
• Short-segment small bowel intussusception seen incidentally on thin-slice CT in asymptomatic patients is thought to be a normal, transient, physiological finding

Complications

• Bowel ischemia and necrosis
• Perforation and peritonitis
• Colonic perforation during pneumatic reduction (rare)
• Hypovolemic shock
• Death if untreated

Summary Table