Notebook: Radiology of Lung Disease 3

INCREASED RADIOLUCENCY, cont'd.
- congenital emphysema is rare
- usually emphysema is correlated w/ lower airway dz
- asthma: difficulty exhaling leads to increased air retained in lungs
- very dark, black lungs may indicate emphysema.
- even if no bronchial pulmonary pattern, may still be feline asthma
- air in stomach: dyspnea has led patient to swallow air.

See focal increased radiolucency more commonly than diffuse.

Air filled structures in the lung
- cavity, cyst, bulla: Cysts are usually congenital with very thin walls. Bullae usually have no apparent walls.
- if related to the bronchi, called bronchiectasis
- term cavitary lesions: masses with air in the center. Differentials same for any other mass. This term can technically be used for any air-filled lesion within the lung. Typically used to describe a lesion with a very thick wall.

Increased radiolucency is less common than increased radiopacity. There are fewer differentials for increased radiolucency.

Why do we have a pleural space:
- main function: keep lungs attached to the chest wall
- small film of fluid creates a negative pressure.
- lubricates lungs (most animals have sm. amt. of fluid in this space)
Side note: elephants lack pleural space.

Pleural effusion
- as soon as we have dz in pleural space, negative pressure will be lost to some degree, causing lung to retract toward the center.
- usually we don't see the pleural space.
- if lungs pull away from chest wall and from each other, we see the pleural space (called pleural fissure line). Vessels taper and disappear; pleural fissure line does not.
- signs: pleural fissure lines, lung lobe retraction, silhouetting.
- bilateral pleural effusion: More common. Top differentials: congestive heart failure, neoplasia, trauma.
- unilateral pleural effusion: Top differential = inflammatory dz

Note to self: see Dr. Seiler's slides for more info.