In pediatric intussusception, which ultrasound finding is classic?

• A. Pseudokidney sign on longitudinal view.
• B. Target (donut) sign on transverse view representing telescoped bowel.
• C. Double bubble sign.
• D. Thumbprint sign on ultrasound.

Answer: (B)

The most characteristic ultrasound finding in pediatric intussusception is the target (donut) sign seen on the transverse view. This appears as concentric rings formed by the telescoped bowel walls and mesentery, giving a classic doughnut-like image that directly represents the invaginated segment within the receiving bowel. While a longitudinal view can show a pseudokidney sign due to overlapping layers, the transverse target sign is the hallmark that makes the diagnosis most straightforward.

The other signs point to different conditions or less specific features. The double bubble sign appears with duodenal atresia, not intussusception, and the thumbprint sign is a nonspecific indicator of mucosal edema or inflammation rather than the characteristic concentric bowel layering of intussusception.