THE CASE

A 13-year-old boy is seen in the Emergency Department (ED) for a cough. He reports a viral illness starting two weeks ago, and four days ago, he was seen in the ED because his symptoms were worsening. At that time, he got a chest X-ray showing a right lower lobe consolidation. He was diagnosed with pneumonia and started on high-dose amoxicillin and azithromycin. However, his symptoms failed to improve, and he now returns with a worsening cough and shortness of breath despite antibiotics. His vitals are notable for a fever of 102.4F, HR 131, BP 112/78, RR 24,and 93% oxygen saturation on room air. A repeat chest X-ray is ordered and read as persistent right lower lobe opacity (Image 1).

**Image 1:** Current chest X-ray on the left, chest X-ray from 4 days ago on the right. Credits: Andrew fried, md

A point-of-care lung ultrasound is performed, with the following findings on the left lung fields.

Point of Care Ultrasound of the Left Lung Fields.

The patient is diagnosed with pneumonia that has failed outpatient treatment and is started on ceftriaxone and admitted to the pediatric hospitalist service.

REVIEW

Shortness of breath and cough are common complaints in the emergency room, both in children and adults. In evaluating these patients, chest X-rays are frequently ordered to evaluate for pneumonia. It is essential to understand the limitations of this imaging modality when interpreting results and making clinical decisions. Several studies have examined the sensitivity of plain films in diagnosing pneumonia, with results ranging from 50-79% sensitivity[1,2,3]. This means that you can miss up to half(!!) of pneumonia cases if you rely on a chest x-ray for your diagnosis. Point-of-care ultrasound offers an alternative imaging modality that is fast, available at the bedside, lacks radiation, and is more sensitive than a chest x-ray. One study from 2012 found lung ultrasound to be 93% sensitive for pneumonia [4]. A meta-analysis from 2019 found lung ultrasound to be 82% sensitive for pneumonia[5]. While these numbers are not perfect, and ultrasound should not be treated as a “rule-out” test for pneumonia, when done correctly, it is a more sensitive and specific test than a chest x-ray. The biggest caveat is that to perform a complete lung ultrasound, all lung fields must be examined, particularly the posterior lobes, as this is where most consolidations will be seen. Furthermore, remember that a lung consolidation on ultrasound does not necessarily mean pneumonia – it generates a differential, including mass, atelectasis, and pulmonary contusion. However, in the right clinical picture (as in the case above), it can be an excellent addition to the workup and can change management.

Image 2: Make sure to examine the lower posterior lung fields, as this is the most common location for consolidations to appear.

Summary:

Chest x-ray is not sensitive for pneumonia. Lung ultrasound – when performed correctly – is more sensitive and specific than chest x-ray. Consider performing a lung ultrasound next time you have a patient in whom you are considering pneumonia.

Want to learn more about Lung Ultrasound? Check out Dr. Avila’s Lecture below

Written by Weeden Bauman, MD

Ultrasound Fellow, Maine Medical Center Emergency Medicine Residency

Edited and Posted by Jeffrey A. Holmes, MD

References:

Hagaman JT, Rouan GW, Shipley RT, Panos RJ. Admission chest radiograph lacks sensitivity in the diagnosis of community-acquired pneumonia. Am J Med Sci. 2009;337(4):236-240. doi:10.1097/MAJ.0b013e31818ad805 [Pubmed]
Ye X, Xiao H, Chen B, Zhang S. Accuracy of Lung Ultrasonography versus Chest Radiography for the Diagnosis of Adult Community-Acquired Pneumonia: Review of the Literature and Meta-Analysis. PLoS One. 2015;10(6):e0130066. Published 2015 Jun 24. doi:10.1371/journal.pone.0130066 [Full Text]
Cortellaro F, Colombo S, Coen D, Duca PG. Lung ultrasound is an accurate diagnostic tool for the diagnosis of pneumonia in the emergency department. Emerg Med J. 2012;29(1):19-23. doi:10.1136/emj.2010.101584 [Pubmed]
Reissig A, Copetti R, Mathis G, et al. Lung ultrasound in the diagnosis and follow-up of community-acquired pneumonia: a prospective, multicenter, diagnostic accuracy study. Chest. 2012;142(4):965-972. doi:10.1378/chest.12-0364 [Pubmed]
Staub LJ, Mazzali Biscaro RR, Kaszubowski E, Maurici R. Lung Ultrasound for the Emergency Diagnosis of Pneumonia, Acute Heart Failure, and Exacerbations of Chronic Obstructive Pulmonary Disease/Asthma in Adults: A Systematic Review and Meta-analysis. J Emerg Med. 2019;56(1):53-69. doi:10.1016/j.jemermed.2018.09.009 [Pubmed]