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Intussusception is a medical emergency where one segment of bowel telescopes into an adjacent segment, creating a bowel-within-bowel configuration that can lead to obstruction, ischemia, and perforation. It is the most common cause of bowel obstruction in children between 6 months and 2 years of age, though it can occur in adults. Early recognition and treatment are crucial to prevent serious complications including bowel necrosis and death.
Intussusception occurs when peristaltic waves cause one portion of bowel (intussusceptum) to invaginate into the lumen of an adjacent distal segment (intussuscipiens). This telescoping effect traps the mesenteric blood vessels between the bowel layers, leading to venous congestion, arterial compromise, and progressive bowel wall edema. If untreated, the process progresses from reversible ischemia to irreversible necrosis, perforation, and peritonitis.
The classic triad of intermittent crampy abdominal pain, vomiting, and bloody 'currant jelly' stools is present in only 20% of cases, making diagnosis challenging. Clinicians should maintain high suspicion in infants presenting with episodic crying, drawing up of legs, and periods of lethargy between pain episodes. Ultrasound showing the pathognomonic 'target sign' or 'donut sign' is the preferred initial imaging, while contrast enema can be both diagnostic and therapeutic in appropriate cases without signs of perforation or peritonitis.
Key imaging focus: Target sign (transverse), pseudokidney sign (longitudinal), trapped mesenteric fat