A mother brings her 11-month-old infant into a rural ED for inconsolable crying. You note the infant lying in the stretcher crying with his knees drawn to his chest. You perform a physical exam and leave the room to order blood work. When you return to the examination room, you note the infant now appears lethargic. An abdominal radiograph is obtained and interpreted by the radiologist as nonspecific. Which of the following diagnostic tests should be performed next?
A) Abdominal CT scan
B) Abdominal ultrasound
C) Nasogastric tube lavage
D) Upper GI series

The correct answer is option B, that is, abdominal ultrasound.

Explanation:

Abdominal ultrasound is the most commonly used diagnostic method for the infants or the child having a suspect intussusception. Ultrasound is considered as the first line of testing for diagnosing the possible case of pediatric intussusception. It reduces the threat of exposing the child to harmful radiations and also assists in eliminating other probable reasons for abdominal pain. Abdominal ultrasound is preferred for diagnosing 98 percent of the intussusception cases.  

Intussusception refers to a condition in which one part of the intestine moves over the neighboring section of the intestine, also known as telescoping. In the condition, the passage of the food or the fluid gets blocked, and in extreme cases, the supply of the blood to the affected part also gets prevented. The condition is most generally witnessed in children below three years of age. The reason for the majority of the cases of intussusception is not known in children.