Transthoracic ultrasound for pleural effusion: traps and tricks

Abstract

Pleural effusion is excess fluid that accumulates between the two pleural layers. Excessive amounts of such fluid can impair breathing by limiting the expansion of the lungs during ventilation. Pleural effusion is still usually diagnosed on the basis of medical history and physical examination, and confirmed by chest x-ray. It is observed in many pulmonary and extra-pulmonary disease; its cause can be relatively benign or definitely malign (cancer), and may require drainage for treatment or for achieving a diagnosis which is available at the bedside by physical examination and Thoracic Ultrasound (TUS). Pleural effusion is detected by TUS even when its volume is very little: it is possible to perform and repeat at bedside, by sufficiently trained physicians. Diagnostic intervention procedures are safer if performed using US probes specifically designed for this use, i.e. with a central hole which allows the co-axial passage of the disposable tools for drainage or Fine Needle Aspiration Biopsy (FNAB). Over-trusting in US criteria not evidence-based and, more important, which are demonstrated to be unreliable when critically re-appraised must be discouraged; reversal of such scarcely validated but recommended practices, which could be harmful for patients, is actively in progress also in this field of medicine. No special trick is needed and no actual trap is present when the assessment of pleural effusion is performed by a sufficiently skilled MD and with a reliable and well set echo machine. Echo-assisted thoracentesis is an excellent procedure when appropriately performed in all its phases, which are: choice of the site of insertion, visualization in real-time during the drainage and serial control during lung re-expansion (so as to avoid pneumothorax).