A 3 month old male presents as a transfer from an outside hospital with a radiographic diagnosis of pneumonia. X-ray is shown on figure 1. On arrival, the patient is in mild respiratory distress, but overall not toxic appearing. Vital signs are as follows: T 100.3°F (37.94°C), HR 145 (sinus) BP 99/59 RR 35. On examination, the patient has scattered and mild wheezing on auscultation, but no focal findings.
You perform a bedside ultrasound to confirm the x-ray findings of pneumonia and find the following:
Based on the x-ray and the ultrasound, what structure is most likely visualized by both modalities?
What is the diagnosis? (Click the button for the answer!)
Thymus; viral infection
Your bedside ultrasound demonstrates the appearance of a thymus. Due to concern for admitting the patient without a clear picture of a bacterial pneumonia, you obtain a second x-ray, which is seen below in figure 2. After the second x-ray is obtained, the admitting pediatric team is consulted and the patient is deemed appropriate for outpatient management of a presumed viral pneumonia.
- The thymus reaches is maximum size at around 5 months of age, and decreases size during the first decade of life. 1
- The thymus has smaller internal echoes with more homogenous and hypoechoic tissue, as well as having discrete borders.1
- Pneumonia has less homogenous tissue with scattered shadowing as well as less discrete borders (shred sign).
- In the pediatric patient, lung ultrasound has been found to be 96% sensitive and 93% specific for pneumonia. 2
The following clip shows an example of a pneumonia in a four-year-old.
For a tutorial on how to perform the examination, check out the 5 minute sono video on pneumonia
Case Courtesy of Russ Horowitz, MD
Peer Reviewed by Ben Smith, MD
References
- Gravel CA, Bachur RG. Point-of-Care Ultrasound Differentiation of Lung Consolidation and Normal Thymus in Pediatric Patients: An Educational Case Series. The Journal of emergency medicine. 2018; 55(2):235-239. [PMID: 29784474]
- Pereda MA, Chavez MA, Hooper-Miele CC. Lung ultrasound for the diagnosis of pneumonia in children: a meta-analysis. Pediatrics. 2015; 135(4):714-22. [PMID: 25780071]
