Intussusception

Intussusception involves the telescoping of a proximal intestinal segment (the intussusceptum) into the lumen of the adjacent distal segment (the intussuscipiens), creating a bowel-within-bowel configuration. The ileocolic type accounts for approximately 90% of pediatric cases, while adult intussusception is more likely enteroenteric and has a pathological lead point in up to 90% of cases. The NP must understand the ischemic cascade: mesenteric venous compression leads to venous congestion, edema, and mucosal hemorrhage; continued progression compresses arterial supply, causing transmural ischemia, necrosis, perforation, and peritonitis. In pediatric populations, viral-induced lymphoid hyperplasia of Peyer patches (from adenovirus, rotavirus, or post-rotavirus vaccination) creates functional lead points. In adults, lead points include Meckel diverticulum, lipomas, leiomyomas, lymphoma, adenocarcinoma, metastatic melanoma, and inflammatory polyps. The NP applies clinical decision-making regarding imaging selection (ultrasound target sign with sensitivity >98% in pediatric patients; CT with IV contrast for adult cases revealing target sign, sausage-shaped mass, or small bowel obstruction pattern), determines candidacy for non-operative reduction (pneumatic or hydrostatic enema for uncomplicated pediatric ileocolic intussusception), identifies contraindications to enema reduction (free intraperitoneal air, peritonitis, hemodynamic instability, prolonged symptoms...