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Practice Pearl Thoracic Ultrasound
Practice Pearls for Performing Pleural
Ultrasound with Focus on Pleural Effusion
and Pleural Thickening
Macarena R Vial 1 and Horiana B Grosu 2
1. Interventional Pulmonology Unit, Clinica Alemana de Santiago-Universidad del Desarrollo, Chile; 2. Department of Pulmonary Medicine, The
University of Texas MD Anderson Cancer Center, Houston, TX, US
U ltrasonography can provide guidance for several diagnostic and therapeutic procedures, and is now considered the standard of care
for the evaluation of patients with pleural diseases. Ultrasonography is a particularly useful tool in the evaluation of pleural effusion and
pleural thickening, with advantages such as portability, low cost, and safety.
Keywords General considerations
Ultrasound, pleural effusion, pleural thickening
Pleural ultrasound examination can be performed in any position: supine or sitting. A low-frequency
phased array transducer of 3.5–5 MHz is generally preferred for evaluation of pleural diseases.
High-frequency linear transducers do not provide acceptable penetration for visualizing deep
structures, but do provide better imaging of the pleural lining and better assessment of pleural
thickness. The operator should adjust the ultrasound settings such as depth, gain, and time-gain
compensation to obtain the best possible image.
Disclosure: Macarena R Vial and Horiana B Grosu have
nothing to declare in relation to this article. This article
is a short opinion piece and has not been submitted
to external peer reviewers. A member of the editorial
board reviewed the article before publication.
Authorship: All named authors meet the International
Committee of Medical Journal Editors (ICMJE) criteria
for authorship of this manuscript, take responsibility
for the integrity of the work as a whole, and have
given final approval to the version to be published.
Open Access: This article is published under the
Creative Commons Attribution Noncommercial License,
which permits any noncommercial use, distribution,
adaptation, and reproduction provided the original
author(s) and source are given appropriate credit.
Received: October 16, 2017
Published Online: December 12, 2017
Citation: US Respiratory & Pulmonary Diseases,
2017;2(1):23–5 Identifying a pleural effusion
Multiple studies have confirmed that the diagnostic accuracy of ultrasound is superior to that of chest
radiography for detection of pleural effusions. 1 Pleural ultrasound can detect physiologic amounts of
pleural fluid and is highly sensitive for effusions of >100 ml. 2
Free-flowing effusions accumulate in the most dependent portions of the thorax. Most commonly
effusions accumulate in the posterio-lateral costophrenic recesses in seated or supine patients, but
they can also accumulate anteriorly in mechanically-ventilated patients in a prone position.
Corresponding Author: Horiana B Grosu, Department
of Pulmonary Medicine, Unit 1462, The University of
Texas MD Anderson Cancer Center, 1515 Holcombe Blvd,
Houston, TX 77030, US. E: firstname.lastname@example.org
Pleural effusions are best evaluated starting at the level of the diaphragm. The transducer should
be placed in a longitudinal plane on the posterior axillary line at the level of the diaphragm with the
transducer orientation marker pointed cephalad.
Support: No funding was received in
the publication of this article.
The following structures must be identified to diagnose a pleural effusion: liver, spleen, diaphragm,
lung, and chest wall. In the absence of pleural fluid, examination of the costophrenic angle will reveal
the diaphragm and underlying organ (liver or spleen), with lung tissue coming into view during deep
inspiration; this is called the curtain sign. 3 This sign, however, does not rule out the presence of
loculated or interlobar effusions.
Quantifying pleural fluid
Several methods have been proposed to quantify the size of pleural effusions, but a precise
estimate of fluid volume on ultrasonography is not possible. The largest study of this to date
found a strong correlation between calculated and actual volumes drained by thoracentesis. 4
This uses the formula of: volume (in ml) = 16 × parietal-to-visceral pleural distance (in mm) at the
level of mid-diaphragm to quantify pleural fluid. In general, we measure the deepest pocket of fluid
in a still picture, or the number of rib spaces where the fluid can be seen by holding the probe
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