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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: hbgrosu@mdanderson.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 TOU CH MED ICA L MEDIA 23