Intussusception at the Ileocolic Junction
The most likely anatomic location is the junction of the ileum and ascending colon (ileocolic junction), which is the classic site for intussusception in infants presenting with this clinical triad.
Clinical Presentation Analysis
The patient's presentation is pathognomonic for intussusception:
- Bilious vomiting indicates intestinal obstruction distal to the ampulla of Vater 1
- Intermittent, colicky abdominal pain with drawing legs to chest represents the classic "paroxysmal" pain pattern 2
- "Currant jelly" stool (blood in diaper) results from venous congestion and mucosal sloughing at the intussusception site 2
- Periods of normal behavior between episodes is characteristic of the intermittent nature of intussusception 2
Anatomic Location
Ileocolic intussusception (ileum telescoping into the ascending colon at the ileocecal junction) accounts for the vast majority of pediatric cases:
- The ileocecal junction represents the transition point where the terminal ileum enters the cecum/ascending colon 3, 4
- This anatomic site has a localized muscle thickening at the base of the ileal papilla, creating a natural "lead point" for intussusception 3
- The ileocecal area is a specialized segment regulating intestinal transit, making it vulnerable to telescoping 5
Why Other Locations Are Incorrect
- Descending colon-cecum junction: These structures are not anatomically adjacent 6
- Ileum-jejunum junction: Would not produce the classic ileocolic intussusception pattern seen with bloody stools 1
- Transverse-ascending colon junction: Colonic-colonic intussusception is rare in infants 4
- Transverse-descending colon junction: Similarly, this represents colonic intussusception which is uncommon in this age group 4
Critical Diagnostic Considerations
This is a surgical emergency requiring immediate evaluation:
- Ultrasound should identify the pathognomonic "target sign" or "donut sign" representing the telescoped bowel 1
- The "whirlpool sign" on ultrasound (clockwise wrapping of mesentery) may be visible, though this is more specific for midgut volvulus 1
- Delayed diagnosis risks bowel ischemia, perforation, and significantly increased mortality 7
Management Pitfall
Do not confuse this presentation with malrotation/midgut volvulus, which typically presents in the first 2 days of life with bilious vomiting but without the intermittent colicky pain pattern or bloody stools 1, 2. The age of presentation and intermittent symptoms clearly point to intussusception rather than malrotation.