Pleural Effusion

Question 1

3 mechanisms of pleural effusion?

Answer 1

• increased drainage of fluid into the space
• increased production of fluid by cells in the space
• decreased drainage of fluid from the space

Question 2

What is intrapleural pressure?

Answer 2

• neg pressure is created in pleural space as thoracic cage enlarges and lungs recoil during normal inspiration
• negative pressure may be lost if fluid collects in pleural space, making the lung unable to expand fully

Question 3

Normal amt of pleural fluid?

Answer 3

• up to 25 ml is normally present, not detectable on conventional radiographs
• pleural effusion: abnorm accum of fluid into pleural space

Question 4

What are the main causes of pleural effusion?

Answer 4

• CHF (venous pressure increased - fluid exceeds hydrostatic pressure)
• liver failure ( decreased albumin = decreased oncotic pressure)
• infection
• atelectasis
• cancer
• trauma

Question 5

What is a hemothorax?

Answer 5

• blood in pleural cavity
• usually b/c of chest injury
• blood vessel ruptures into pleural space or bulging area into aorta (aortic aneurysm) leaks blood into pleural space
• can occur as a result of bleeding from ribs, chest wall, pleura and lung

Question 6

Diff types of pleural fluid?

Answer 6

• transudate: serum w/o protein
• exudate: protein in fluid; infection, inflammation
• empyema: infection - pus accum
• chyle: lymph fluid (milky appearance)
• hemothorax

Question 7

How much fluid needs to be present to be visible on XR? What position can confirm fluid? Other signs on imaging?

Answer 7

• 250 ml to be seen on PA CXR
• Lateral decubitus on affected side will almost always confirm fluid
• fluid will sit in Costophrenic angles or fissures
• pleural fluid becomes traped by pleural adhesions, form unusual colelctions along chest wall or in lung fissures - US or CT is uesful to locate loculated or small effusions
• massive pleural effusion: is usually caused by cancer but has been observed in TB and other diseases
• CT scanning is useful in free or loculated pleural fluid