FM Radiology Case - Pleural Effusion Flashcards
What is the purpose of the thin film of fluid in the normal pleural space?
Allows the visceral and parietal pleura to glide over each other during respiration
What is a pleural effusion?
Excess fluid accumulation in the pleural space
List the types of fluid that can accumulate in the pleural space.
Transudate, exudate
Pus, blood, chyle, urine
Cholesterol
True or false - the type of fluid of a pleural effusion can be distinguished in plain CXR.
False - they all look the same.
What is the mechanism by which transudative fluid accumulates in the pleural space?
Hydrostatic pressure changes, as in CHF, cirrhosis, and hypoalbuminemia
What is the mechanism by which exudative fluid accumulates in the pleural space?
Inflammation of the pleura, as in malignancy, RA, etc.
What is the mechanism by which pus accumulates in the pleural space?
Empyema from infections
What is the mechanism by which blood accumulates in the pleural space?
Trauma
What is the mechanism by which chyle accumulates in the pleural space?
Rupture of the thoracic duct
What is the mechanism by which urine accumulates in the pleural space?
Urinothorax in hydronephrosis
List the imaging criteria for pleural effusion on CXR.
- Homogenous density
- Density in a dependent position
- Silhouette of upper limit of density (lack of identifiable diaphragm - silhouette sign)
- Loss of silhouette
- Mediastinal shift
How does the density of a pleural effusion change in upright, lateral, lateral decubitus, and supine positions?
Upright - costophrenic angle (PA)
Lateral - anterior and posterior portions of gutter
Lateral decubitis - along the sides
Supine - along posteriorly, giving diffuse haziness on the side of the effusion
How does the mediastinum shift with effusion vs. atelectasis?
Effusion - shifts to the opposite side of the effusion
Atelectasis - pulled to the same side
Compare the hemithorax in pleural effusion vs. atelectasis.
Pleural effusion - larger hemithorax
Atelectasis - smaller hemithorax
Massive pleural effusion is often due to ___.
Malignancy
In ___, effusions are bilateral and more on the right.
CHF
Most effusions start as ___ and can be easily missed.
Sub-pulmonic
Loculated effusion is ___ unless proven otherwise.
Empyema
When should loculation be considered?
When a density is considered to be fluid and does not correspond to anatomical location of fissures; not in the gravity dependent position
When should a lateral decubitus film be ordered?
Confirm pleural effusion as with small or sub-pulmonic effusions; evaluate underlying lung; most of the time it is unnecessary
What other imaging procedures can be of value in evaluating a pleural effusion?
U/S and CT
How is U/S used to evaluate a pleural effusion?
Ideal for localizing loculated or small effusions for thoracentesis; can also guide thoracentesis and placement of drainage tubes
How is CT scan used to evaluate a pleural effusion?
Can detect pleural masses and lung lesions not evidence in CXR; can also guide drainage placement
When should radiologic assistance be used to tap effusions?
Small effusions and loculated effusions
