Transthoracic ultrasound in the assessment of pleural and pulmonary diseases: use and limitations

Abstract

Interest in transthoracic ultrasound (US) procedures increased after the availability of portable US equipment suitable for use at the patient's bedside. It is possible to detect space-occupying lesions of the pleura, pleural effusion, focal or diffuse pleural thickening and subpleural lesions of the lung, even in emergency settings. Transthoracic US is useful as a guidance system for thoracentesis and peripheral lesion biopsy, where it minimises the occurrence of pneumothorax and haemorrhage. Transthoracic US imaging is strongly influenced by physical interaction of the ultrasonic beam at the tissue/air interface, which gives rise to reverberations classified as simple (A-line), "comet tail" and "ring down"(B-line) artifacts. Although these artifacts can be suggestive of a disease condition, they are essentially imaging errors present even in normal subjects and in empty-pleura post-pneumonectomy patients. In order to clarify some confusion and to report on the state of the art, we present a review of the literature on transthoracic US in diseases of the pleura and peripheral lung regions and our own clinical experience over 3 decades. The review focuses on quality assurance procedures and their value in diagnostic imaging and patient monitoring and warns against possible inappropriate indications and misleading information. Thoracic US is much more than "fishing for the moon in the well".

Transthoracic ultrasound for pleural effusion: traps and tricks

“…The 2-8 MHz multifrequency probes, which can be considered the more recent development, are useful for a preliminary diagnostic and, often, even for a conclusive report. The application (preset) for the chest is not normally preinstalled in any ultrasound system and therefore it is necessary to start and save in memory a preset for the ultrasound pleuro-pulmonary assessment; this step is necessary for both the convex and the linear (16)(17)(18). Color and pulsed Doppler are not critical for a first approach ultrasound examination, because are both very often affected by respiratory motion artifacts and heart rate, flash artifacts, for example (19), even optimizing the setting (PFR).…”

“…TUS is always complementary to the thoracic radiographic study (Chest X-Rays, i.e. CXR) and/or to chest CT scan (15,16), and therefore should never be considered end point of a diagnostic process and workup (17). Pleuro-pulmonary TUS can be a key aid for the guidance of interventional diagnostic methods in the field of pulmonology, such as pleural and lung biopsies and pleural drainage (13, 14); both procedures are even less invasive due to the use of probes with a central passage of the fine needle devices, which allow the best approach to interventional pulmonology.…”

“…Some authors have developed formulas for calculating the volume of the effusion (27), the amount of compression-related lung atelectasis and the degree of organization of the pleural fluid. Although some authors have tried to calculate it, the quantification of the effusion by ultrasound is not really reliable since the method is two-dimensional and any calculation formula cannot provide a safe and reliable quantification of three-dimensional real volume and quantity (16). In clinical practice, ultrasound, however, may be sufficient to determine the greater longitudinal and transverse diameters of the effusion (Figure 2).…”

“…Pleuro-pulmonary TUS can be a key aid for the guidance of interventional diagnostic methods in the field of pulmonology, such as pleural and lung biopsies and pleural drainage (13,14); both procedures are even less invasive due to the use of probes with a central passage of the fine needle devices, which allow the best approach to interventional pulmonology. Pleuropulmonary TUS is being increasingly used in Emergency Departments, in all those cases in which such additional examination is a useful guide for the subsequent and immediate diagnostic approach for further study, which are always complementary to chest physical examination and to other established imaging modalities (16).…”

Letter to the Editor

“…To the Editor, We read the article by Dr. Sperandeo and colleagues [1] with great interest. A highlight of the article is the detailed focus on equipment settings and technique, and explanations for the physical origins of artifacts.…”