One segment of bowel telescopes into the next, most often ileocolic
Expansion
- The intussusceptum (the entering segment) telescopes into the intussuscipiens (the receiving segment)
- Most are ileocolic, with the terminal ileum passing through the ileocaecal valve
The mesentery is dragged in with the bowel, so the vessels are compressed. This produces venous congestion, then mucosal bleeding, giving the classic redcurrant jelly stool, and finally arterial compromise and infarction.
Presentation in children (peak 6 months to 2 years) is colicky pain with drawing up of the legs, vomiting and a sausage-shaped mass in the right upper quadrant, with an empty right iliac fossa (Dance’s sign). Ultrasound shows the target or doughnut sign.
The lead point distinction matters: in children it is usually hypertrophied lymphoid tissue after a viral illness, and air or contrast enema reduction usually succeeds. In adults a tumour is the lead point in most cases, so resection is required.