Category: 9. Pediatric Abdominal Ultrasound Applications

Intussusception occurs when a segment of bowel “telescopes” onto another segment, or onto itself, because of peristalsis. It is a common cause of acute abdomen in children, the most common cause of intestinal obstruction in children, and has significant complications, such as bowel necrosis, making its timely detection imperative (Edwards).

The classic triad of intussusception is intermittent abdominal pain, vomiting, and the presence of a right upper quadrant mass. When paired with the presence of gross or occult bleeding on rectal exam, this has a high positive predictive value for intussusception.

The most common ultrasound findings for intussusception are:

• Target sign: inflamed bands of hyperechoic mucosa and relatively hypoechoic submucosa are visible.
• Pseudokidney sign: fat-containing mesentery is dragged into the intussusception, resembling the kidney hilum. The resultant longitudinal appearance is of a small kidney.

Pyloric stenosis refers to idiopathic, hypertrophic thickening of the py­loric musculature, which progresses to gastric outlet obstruction. Symptoms typically present at 2-8 weeks of age. Classically, this will feature a neonate with non-bilious, projectile vomiting. You may also appreciate an olive-sized mass in the right upper quadrant on physical exam.

On ultrasound, the diagnosis of pyloric stenosis is based on 2 measurements: a pyloric muscle diameter > 4mm, and a pyloric canal length > 14mm.

Abdominal ultrasound has numerous pediatric applications. Here, we focus on appendicitis vs mesenteric adenitis, pyloric stenosis, and intussusception.

Appendicitis vs Mesenteric Adenitis

Our technique for detecting appendicitis is described in the section above.

An important differential diagnosis in appendicitis includes mesenteric adenitis. In contrast to appendicitis, ultrasound findings for mesenteric adenitis will be the absence of a visibly enlarged appendix, and the presence of enlarged mesenteric nodes, as pictured below.