Imaging: Pleural Space + Mediastinum

Question 1

pneumothorax on radiographs

Answer 1

• bilateral (communicates through mediastinum)
• dorsal elevation of cardiac silhouette w/ underlying radiolucent region
• retraction of the lung lobes from the thoracic wall

Question 2

tension pneumothorax

Answer 2

severe pneumothorax caused by increased pressure in the pleural space

• unilateral (lung collapse)
• mediastinum shifts away from the collapsed lung

Question 3

pleural effusion

Answer 3

• homogenous ST opacity in the ventral thorax
• loss of cardiac margins
• dorsal retraction of lung lobes w/ ST opacity between lungs and wall
• pleural fissure lines between lobes

Question 4

how can you differentiate between pulmonary edema and pleural effusion

Answer 4

use VD shot

pleural effusion will distribute throughout the wider area of the dorsum

Question 5

pleural effusion on large animal radiographs

Answer 5

use lateral view only
- homogenous ST opacity
- similar to alveolar pattern but without air bronchogram
- fluid line between ventral and dorsal aspect
- loss of cardiac silhouette margins

Question 6

ddx for pleural effusion

Answer 6

R sided heart failure
neoplasia
hemothorax
chylothorax
pyothorax

Question 7

what is a unilateral pleural effusion likely to be

Answer 7

inflammatory (pyothorax) due to closure of mediastinal fenestrations

Question 8

chronic pleural effusion on radiographs

Answer 8

rounded lung borders due to pleural fibrosis
- usually chronic chylothorax or pyothorax

Question 9

diaphragmatic rupture on radiographs

Answer 9

• unilateral pleural effusion
• irregular diaphragm outline
• abdominal organs in thoracic cavity

Question 10

peritoneal pericardial diaphragmatic hernia

Answer 10

congenital failure of the diaphragm to close
- bilateral
- cardiomegaly
- bowel loops in pericardium

Question 11

where is the mediastinum

Answer 11

space in between the two layers of mediastinal pleura

contains heart, great vessels, trachea, esophagus, lymph nodes, and thymus

Question 12

what does the mediastinum communicate with

Answer 12

neck and retroperitoneal space

Question 13

pneumomediastinum

Answer 13

• increased visibility of the cranial vena cava/other great vessels
• increased visibility of esophagus and tracheal walls

Question 14

cranial mediastinal masses appearance

Answer 14

• wide cranial mediastinum
• dorsally elevated trachea

Question 15

cranial mediastinal mass ddx

Answer 15

lymphoma
thymoma

Question 16

lymphadenopathy on radiographs

Answer 16

• enlarged LNs dorsally, ventrally, or both to the trachea

If both sternal & tracheobronchial: lymphoma or fungal disease

If sternal only: abdominal disease

Question 17

heart base mass appearance and DDX

Answer 17

increased ST opacity at the heart base

DDX: chemodectoma, hemangiosarcoma

Question 18

caudal mediastinal mass

Answer 18

mass between heart and diaphragm

Question 19

megaesophagus

Answer 19

diffusely gas dilated esophagus

Question 20

persistent R aortic arch

Answer 20

• food/foreign material in cranial esophagus
• enlarged cranial mediastinum
• focally deviated trachea to the left

Question 21

hiatal hernia

Answer 21

• caudodorsal, dynamic changes in opacity

take multiple radiographs to determine if present

Question 22

thoracic wall masses

Answer 22

• broad base (sessile base) centered on ribcage
• rib involvement (lysis or displacement)

Question 23

mediastinal masses

Answer 23

• centrally located
• tracheal displacement possible

Question 24

pulmonary masses

Answer 24

• right or left sided
• better visualized on one lateral view over the other
• no rib changes or tracheal displacement