Intussusception

Overview

•Proximal bowel (intussusceptum) telescopes into distal bowel (intussuscipiens) causing obstruction and vascular compromise

•Most common in infants aged 3 months - 2 years; peak 5-9 months; 2x more common in boys

•Majority idiopathic (hypertrophy of Peyer's patches post-viral); beyond age 2, pathological lead point more likely

•Most common site: ileocolic (ileocaecal junction)

•Pathological lead points: Meckel's diverticulum (most important), polyps, lymphoma, HSP submucosal haematoma

Presentation

•Colicky abdominal pain - episodic every 15-20 minutes; infant screams, draws up knees, then appears well between episodes

•Vomiting - initially non-bilious, becomes bilious as obstruction progresses

•Redcurrant jelly stool - blood and mucus from mucosal sloughing; late sign indicating venous congestion and mucosal ischaemia

•Sausage-shaped mass - palpable in the right upper quadrant

•Lethargy, pallor, abdominal distension in advanced cases

🎯

The classic triad (colicky pain + redcurrant jelly stool + sausage-shaped mass) is only present in a minority of cases. Redcurrant jelly stool in any question stem is a near-diagnostic clue.

Investigations

🥇 First-line

•Abdominal ultrasound - investigation of choice; shows target/doughnut sign (transverse) and pseudokidney/sandwich sign (longitudinal)

🏆 Gold standard

•Therapeutic enema (air or contrast) - simultaneously diagnostic and therapeutic; confirms reduction when air/contrast flows freely into the terminal ileum

•Bloods: FBC and U&Es - neutrophilia, electrolyte imbalance from vomiting

•AXR - dilated proximal loops, paucity of distal gas, fluid levels; may be normal early; excludes perforation (free air)

•CT abdomen - second-line; used in adults or if USS inconclusive; identifies lead point

Management

•Resuscitation first: IV fluid resuscitation + nasogastric tube ('drip and suck') for all children

•Definitive: Air or contrast enema reduction under fluoroscopic guidance

🚨

Absolute contraindications to enema reduction: bowel perforation, peritonitis, haemodynamic instability, radiological signs of bowel infarction - these require urgent surgery.

Complications

•Bowel ischaemia, necrosis, perforation - risk increases with delayed diagnosis

•Peritonitis and sepsis - sequelae of perforation or transmural ischaemia

•Recurrence - 5-15% of cases, most commonly within 24-72 hours of reduction; more common after enema than surgical reduction

💡

Mortality in the UK is less than 1% with prompt treatment. Early reduction before bowel ischaemia avoids the need for resection.