Mediastinum Flashcards
Mediastinum
Everything between the right and left pleural sacs bounded by mediastinal pleura
Extends from the thoracic inlet to the diaphragm
NOT A CLOSED CAVITY!
What are the three Mediastinal reflections?
Cranioventral
Caudoventral
Caval
Cranioventral mediastinal reflection
border between the right cranial lung lobe and the cranial part of the left cranial lobe
What does the thymus look like in a VD?
A sail!
Caudoventral mediastinal reflection
border between the accessory lobe and the left caudal lobe
What lives in the Caudoventral mediastinal reflection?
The phrenic nerve
What lives in the Cranioventral mediastinal reflection?
Thymus
What mediastinal organs are visible?
Heart Trachea Caudal Vena Cava Aorta Thymus Esophagus
What mediastinal organs are NOT visible?
Cranial Vena Cava Azygos vein Lymph nodes Nerves Small arteries and veins
Which do you see on radiographs, Cranial or Caudal Vena Cava?
Caudal Vena Cava!
What causes Mediastinal shift?
Atelectasis
How do you dissociate Atelectasis from Lung Disease?
Lung opacity, no heart shift = disease
Lung opacity, heart shift = atelectasis
What could be the reason for a cranioventral mediastinal mass?
Mediastinal LN
Thymus
Sternal LN
Cyst
What could be the reason for a hilar mediastinal mass?
Tracheobronchial LN
Left Atrium
Heart Base tumor
What could be the reason for a dorsal mediastinal mass?
Esophagus
What do the Cranial Mediastinal Lymph nodes drain?
Thoracic wall
Trachea
Thyroid
What do the Tracheobronchial Lymph nodes drain?
Lungs
What do the Sternal Lymph nodes drain?
Mammary glands
Thoracic wall
peritoneum
What could an enlarged sternal lymph node mean?
Peritoneal disease
Hemorrhage
Ruptured Splenic Tumor
What does the “Bow Legged Cowboy” sign mean when seen on a radiograph?
The tracheobronchial lymph node has swollen
Can you see a mediastinal mass with pleural fluid?
NO! DRAIN THE FLUID AND RE-RADIOGRAPH!
How does the trachea appear with Tracheobronchial Lymphomegaly?
Ventral angulation of the tracheal bifurcation
What happens to the trachea when the left atrium is enlarged?
The trachea is angled upward
What happen to structures with Pneumomediastinum?
structures become more conspicuous that you wouldn’t normally see
Ex: Azygous vein
What happens if Pneumomediastinum progresses?
Pneumothorax
Can Pneumothorax progress to Pneumomediastinum?
NO!
What view is the best to see Pneumomediastinum?
Lateral view
What two ways can cause Pneumomediastinum?
Retrograde slow along the airways from intrapulmonary rupture
Hole in Trachea
Neck wound
What causes a hole in the trachea?
Bite wound
Jugular vein puncture
Transtracheal aspirate
Endotracheal tube cuff overinflation
Macklin effect
gas in the lung parenchyma getting out of the bronchi and vessels and into the mediastinum
Which structures become visible with Pneumomediastinum?
Adventitial border of the trachea
Ascending aorta
Left Subclavian artery
Brachiocephalic trunk
What other clinical signs can you see with Pneumomedistinum?
Air under the skin - “crunchy” feeling
Animal appears twice its normal size
What are the different types of fluid seen in the mediastinum?
Hemorrhage
Exudate
