The most common known cause of intussusception in children is .
USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
An 18-month old boy comes to the emergency department with an 8-hour history of non-bilious, non-projectile vomiting and abdominal pain.The pain began suddenly and was intermittent with periods of complete resolution in between episodes. His parents note that he had several bowel movements containing both blood and mucus. Two weeks ago, he had an upper respiratory infection, but he has otherwise been healthy and developing appropriately. He is curled in pain on the examination table with his knees to his chest. Physical examination shows right upper and lower quadrant tenderness to palpation without rebound tenderness or tympany. A sausage-shaped mass can be palpated in the right upper quadrant. Rectal examination shows normal sphincter tone and the fecal occult blood test is positive. Barium enema is done, showing intussusception of the distal segment of ileum into the cecum. Which of the following intestinal layers within the entrapped segment of the ileum is most vulnerable to ischemia from lack of arterial blood supply?