The pleural effusion, formerly called pleural spill, is an accumulation of fluid in the pleural space, as a consequence of an imbalance between the formation and reabsorption of such fluid, or due to an alteration in the drainage to lymph nodes. The purpose of this bibliographic review is to establish the importance of the use of ultrasound in pleural diffusion diagnosis. The authors discuss the use of ultrasonography in the diagnosis and therapeutic approach of this disease, and stress the importance of ultrasonography in chest diseases diagnosis, its advantages, limitations and disadvantages when compared to the common x-ray, computed tomography and physical examination. The authors also discuss the definition of pleural effusion, its physiopathology, morbidity, mortality, main causes and clinical presentation. The examination technique is systematically approached both by thoracic and abdominal pathways.

Keywords: Pleural effusion, Pleural spill, Ultrasound