Pediatric Ultrasound Tricks of the Trade: Abdominal Ultrasound - Emergency Ultrasound Section Newsletter, February 2012
Samuel Lam, MD, RDMS
Assistant Ultrasound Director
Advocate Christ Medical Center
Russ Horowitz, MD, RDMS
Pediatric Emergency Ultrasound Director
Children’s Memorial Hospital
Pediatric bedside ultrasound applications have been gaining in popularity recently. There are several reasons for this, such as better training in emergency medicine residencies and pediatric emergency medicine fellowships, advantages of a no-radiation bedside tool, and the growing literature on various pediatric applications. While many of the “adult” applications can be generalized to the pediatric population, there are some unique pediatric bedside ultrasound applications that require learning of new skill sets. Hence we have developed this section to share such knowledge.
Our first article aims to give the audience some succinct pointers on three pediatric abdominal ultrasound applications. Generally, a high frequency probe is recommended because the anatomical structures we are interested in tend to be quite shallow.
Intussusception Classic teaching is that children with intussusception have a mass in the right upper quadrant and empty right lower quadrant. Although the emergency physician won’t be performing the barium enema reduction, bedside sonographic diagnosis helps prioritize radiology workflow. In hospitals where radiologists are unable to perform intussusception reductions, a bedside diagnosis will help facilitate transfer to an appropriate facility. “I performed a bedside ultrasound and visualized the intussusception” carries more weight than “I think he may have intussusception.”
- Start your search in the RUQ to visualize leading edge of intussception
- Graded compression: Slow, steady pressure on the abdominal cavity in order to displace overlying bowel gas
- Follow the colon (fig.1) or “lawn mower approach” (fig. 2)
| Figure 1
|| Figure 2
Typical Patterns to look for:
- Doughnut/ Target sign: Layers of invaginated bowels seen in cross section (fig. 3)
- Pseudokidney sign: in oblique view (fig. 4)
- Pancake sign: stacked layers of bowel in longitudinal view (fig 5)
Potential Mimics/ Confounders: bowel wall hematoma, enterocolitis, psoas muscle, inflammatory bowel disease
Tip: Stool in colon can mimic intussusception (fig. 6). Though it can be echogenic on ultrasound, stool does not give the layered, concentric view typical of intussusception.
Appendicitis Applies to big kids as well.
- Graded compression
- Scan at point of maximal tenderness
- Most commonly lie between iliac vessels and psoas muscle.
Typical Pattern to look for:
- Non compressible blind ending tubule ≥ 6mm (fig. 7)
- Target sign on cross section (fig. 8)
- Focal free fluid collection (fig. 9)
- Fecalith occasionally (fig. 10). Fecaliths may not shadow!
- Hyperermia surrounding appendix.
Potential Mimics/Confounders: Inflammation from Crohn’s disease/tuboovarian abscess can cause serosal edema and thickening of appendix, inflamed Meckel’s diverticulum
Tips: Specificity high but sensitivity low. Failure to visualize appendix ≠ no appendicitis
Hypertrophic Pyloric Stenosis
- Pylorus is medial to the gallbladder.
- Pylorus is lateral and anterior to the aorta/ superior mesenteric artery
- Find the fluid-filled stomach and follow it distally to the pylorus
Typical Pattern to look for:
- Pyloric muscle is hypoechoic on ultrasound
- Target sign on transverse view (fig. 11)
- Pyloric muscle thickness ≥ 3mm (fig. 12)
- Pyloric channel length ≥ 15 -18 mm (fig.13)
- Lack of gastric emptying
Potential Mimics/Confounders: Tangential section of pyloric muscle can give a false positive result, overdistended stomach can displace the pylorus posteriorly and give a false negative result. Pylorospasm will show a thickened pylorus and delay gastric emptying giving a false positive study.
Tip: Roll child into lateral decubital position and feed child. The stomach will become hypoechoic filled with small hyperechoic air bubbles. Hold probe over pylorus. In children without pyloric stenosis, you will see a steady stream of fluid rush through the pylorus into the small bowel.
Questions? Email Samuel Lam or Russ Horowitz .