Which term describes the accumulation of fluid within the pleural space?

Pleural effusion is the term used to describe the accumulation of fluid within the pleural space, which is the cavity between the lungs and the chest wall. This condition can lead to symptoms such as difficulty breathing and chest pain due to pressure on the lungs. It can result from various causes, including infections, heart failure, or malignancies, and is a significant clinical finding that requires further investigation and management.

The other terms are related to respiratory and medical conditions but refer to different issues. Atelectasis pertains to the collapse or incomplete expansion of the lung or a part of it, preventing proper air exchange and leading to difficulties in ventilation. Extirpation is a surgical term that means the removal of tissue or an organ, while adhesion refers to the abnormal fibrous connections that can form between tissues or organs, which can also impact respiratory function but not in the context of fluid accumulation. Therefore, pleural effusion specifically identifies the condition of fluid accumulation in the pleural space, making it the correct answer.