Invagination or telescoping of 1 segment of gastrointestinal tract and its mesentery (intussusceptum) into lumen of adjacent distal segment (intussuscipiens)

Bowel within bowel appearance: Concentric parallel rings of bowel wall (target, doughnut, or bull’s-eye sign)

Echogenic crescent of intussuscepted mesenteric fat (crescent within doughnut sign)

Central lead point lesion or lymph nodes

Layering of fluid trapped between compressed bowel segments

Mesenteric vessels trapped between entering and returning limbs of intussusceptum

Reduced or absent mural vascularity of intussusceptum indicative of vascular compromise → ischemia with risk of infarction and perforation

Ultrasound: 1st line in children

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  High sensitivity (98-100%) and specificity (88-100%)

CT: Often 1st investigation in adults presenting acutely; high sensitivity and specificity and accessible

Tumor, inflammation, infection

Occurs anywhere from stomach to rectum

Children: Idiopathic in 95%; enlarged lymphoid tissue post infection; rare before 3 months of age

Adults: Identifiable etiology in 90%

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  Lead point, celiac, Whipple disease, or cystic fibrosis

  
  
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  Transient intussusception: Nonobstructing, spontaneous resolution

Children (95%): Most common abdominal surgical emergency

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  Acute pain, palpable mass, “red currant jelly” stools

  
  
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  Accounts for 80% cases of infantile obstruction; lead point uncommon

Adults (5%): Insidious, vague abdominal symptoms, vomiting, red blood in stool

< 2% adult obstructions

Complications: Obstruction, bowel ischemia, or infarction

Surgery indicated where lead point identified or complications evident on CT

Large-volume ascites, debris, and free gas are suggestive of perforation