Mediastinum

Question 1

Mediastinum

Answer 1

The space between right and left pleural sacs; bounded by mediastinal parietal pleura
extends from thoracic inlet to diaphragm
not a closed cavity- communicates with neck and retroperitoneal space
Fenestrated; usually does not contain unilateral disease

Question 2

Mediastinal reflections

Answer 2

locations where the mediastinum deviates from the midline
Cranioventral
Caudoventral
Caval; cant see

Question 3

Cranioventral mediastinal reflection

Answer 3

Between the right cranial lung lobe and the cranial part of the left cranial lobe
the left lung curves to the right, cranial to the right cranial lung lobe
Creates a curve in the cranioventral mediastinum

Question 4

Caudoventral mediastinal reflection

Answer 4

Border between the accessory lobe (R lung) and left caudal lobe (L lung)
The medial aspect of the accessory lobe crosses midline pushing mediastinla pleura to the left

Question 5

Mediastinal organs normally seen

Answer 5

Heart, trachea, Caudal vena cava, aorta, esophagus (sometimes), thymus in young

Question 6

Mediastinal organs not normally visible

Answer 6

cranial vena cava
azygos vein
lymph nodes
nerves
various small arteries and veins

Question 7

Mediastinal abnormalities

Answer 7

Shift, mass, gas, fluid

Question 8

Mediastinal abnormalities- shift

Answer 8

caused by: atelectasis- most common cause
Large masses
displacement of heart is most reliable sign

Question 9

Mediastinal abnormalities- mass

Answer 9

common causes: enlarged lymph nodes, thymus, esophagus enlargement
Features: on midline or in a reflection
displace another mediastinal organ
Cranioventral: Cr mediastinal LN; thymus; sternal LN; cyst
Hilar: tracheobronchial LN, LA, heart base tumor
Dorsal: esophagus

Question 10

Cranial mediastinal LN drainage

Answer 10

thoracic wall, trachea, thyroid

Question 11

Tracheobronchial LN drainage

Answer 11

lungs

Question 12

Sternal LN drainage

Answer 12

mammary glands, peritoneum

Peritoneal disease may cause sternal lymphadenopathy

Question 13

Dx cause of mediastinal mass

Answer 13

rule outs can be narrowed based on location
Sonography or CT may help
Usually need cytology

Question 14

Confounding effect of pleural fluid

Answer 14

prevents identification of mediastinal mass
Need to take additional steps
Drain fluid and re reradiograph
Ultrasound

Question 15

Pneumomediastinum

Answer 15

Mediastinal structures become more conspicuous due to contrast provided by mediastinal gas
Structures not normally visible are seen
Pneumomediastinum can progress to pneumothorax if distension severe
Pneumothorax will not progress to pneumomediastinum
Lateral view= money shot

Question 16

Pneumomediastinum- causes

Answer 16

Skin wound in neck with caudal dissection of gas into mediastinum
Hole in trachea with caudal dissection of gas into mediastinum (bite wound, jugular vein puncture, endotracheal tube cuff over inflation)
Intrapulmonary tear with air leakage along airways into mediastinum (visceral pleura intact, occurs commonly after blunt trauma, of excessive PPV)

Question 17

Macklin effect

Answer 17

Alveolar rupture inside lung
Air leaks out to mediastinum
then back into pleural space and sub q space to go all over body

Question 18

Pneumomediastinum- makes organs visible

Answer 18

adventitial border of trachea
ascending aorta
left subclavian artery
Brachiocephalic trunk

Question 19

Mediastinal fluid

Answer 19

Not common
hemorrhage-coagulopathy
exudate- FIP, esophageal rupture