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MediastinumMediastinumEsophagus Esophagus

Trachea Trachea

VMB 960

2/28/2011

Mediastinum Mediastinum -- definitiondefinition

Everything between right & left pleural sacs; bounded by mediastinal pleura

Extends from thoracic inlet to diaphragm

Fenestrated; may not contain unilateral disease

Not a closed cavity– Communicates with neck and retroperitoneal space

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Mediastinal ReflectionsMediastinal Reflections

CranioventralCaudoventralCaval; can’t see

Cranioventral Mediastinal ReflectionCranioventral Mediastinal Reflection

Border between the right cranial lung lobe and the cranial part of the left cranial lobe

Cranially, the left lung extends to right

Caudally, the right lung extends to left

Rt. Lung

Lt. Lung

Left SideRight Side

Mediastinum is pushed to the left between

lobes

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Mediastinal Organs Mediastinal Organs Normally SeenNormally Seen

Heart

Trachea

Caudal venal cavaCaudal venal cava

Aorta

Thymus (young animals)

Esophagus (sometimes - left lateral)

Mediastinal AbnormalitiesMediastinal Abnormalities

Lymph nodesEsophageal disordersTracheal disorders Thymic massesEctopic thyroid tissueCystsFluid

Things to confuse with Things to confuse with mediastinal lymphomegalymediastinal lymphomegaly

Heart base mass

Mediastinal cyst

Some other mediastinal masses

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Normal Thymus -

young dogdog

Mediastinal Lymph NodesMediastinal Lymph Nodes

Cranial Mediastinal

HilarHilar

Sternal

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Mediastinum Mediastinum Lymphomegaly

Mediastinal CystsMediastinal Cysts

More common in catsAbnormal development of pharyngeal

(branchial) cleftsUltrasoundUltrasound

Large mediastinal cyst confirmed with u/s

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Mediastinal FluidMediastinal Fluid

Not common

Hemorrhage–Coagulopathyg p y

Exudate–FIP

–Esophageal rupture

Mediastinal HemorrhageMediastinal Hemorrhage

Usually a coagulopathy

Rodenticide toxicity

Usually craniodorsal

Can result in life threatening tracheal compression

Can also be submucosal in trachea

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PneumomediastinumPneumomediastinumHole in Trachea

– Bite wound

– Transtracheal aspirate

E d t h l t b ff i fl ti– Endotracheal tube cuff overinflation

Neck Wound- Jugular vein puncture

Retrograde flow along airways from intrapulmonary rupture

PneumomediastinumPneumomediastinum

Mediastinal structures easy to see – (-) silhouette sign

Pneumomediastinum can progress to pneumothorax if distension severe

Pneumothorax is very unlikely to progress to pneumomediastinum

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Pneumomediastinum (etc)

Mediastinal structuresreadily visible

•Adventitial border of trachea

•Ascending aorta

•Left subclavian artery

•Brachiocephalic trunk

Trachea and BronchiTrachea and Bronchi

Tracheal collapse–IntrathoracicExpirationp

–ExtrathoracicInspiration

HypoplasiaEffect of neck position

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Dynamic Airway Collapse

Complete intrathoracic tracheal

collapse

Trachea Trachea -- MiscellaneousMiscellaneous

Head positionVentral flexion of head and neck

Hypoplastic trachea

- Bulldog predisposed

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EsophagusEsophagus

Is a conduit for ingesta

Functional sphincter at both endsboth ends–Crichopharyngeal

–Gastroesophageal

Dorsal to trachea

EsophagusEsophagusNormally not visible on survey

radiographs

– Air in mediastinum will provide contrastcontrast

Trauma

Jugular venipuncture

Occasionally small amount of gas or fluid, especially in left lateral view

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EsophagramEsophagramValuable for assessing

esophageal function and structureEasy and safe to performIndications

–Regurgitation–Dysphagia–Survey radiographic findings

NEVER…NEVER…give contrast medium give contrast medium ggwithout first making without first making survey radiographssurvey radiographs

The Esophagram: The Esophagram: When to give whatWhen to give what

Usually barium liquid and barium soaked kibble or barium and A/D is used

Rule out esophagitis – Paste and liquid are probably betterq p y

Rule out a vascular ring anomaly– Liquid and barium/food mixture

Rule out esophageal laceration – Do not use barium – Use water soluble iodine (nonionic)

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Normal Canine EsophagramNormal Canine Esophagram

Normal Canine EsophagramNormal Canine Esophagram

Normal Feline EsophagramNormal Feline Esophagram

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MegaesophagusMegaesophagus

Segmental vs. generalized

Congenital vs. acquired

Radiographic Signs of Radiographic Signs of Generalized MegaesophagusGeneralized Megaesophagus

Esophagus may be gas or fluid filled

Trachea is displaced ventrallyp y

Converging “funnel” shaped opacities in caudal thorax on VD

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Assess Assess esophagus esophagus on DV / VDon DV / VD

Generalized MegaesophagusGeneralized Megaesophagus

Congenital

Myesthenia Gravis (MG)

Hypothyroidism

Intracranial mass

Toxicity(MG)

Thymoma + MG

Addisons Disease

Neuromuscular disease

Toxicity

Stricture at gastroesophageal junction

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Radiographic Signs of Radiographic Signs of Segmental MegaesophagusSegmental Megaesophagus

Focal mass effect or gas accumulation

Trachea displaced ventrally ifTrachea displaced ventrally if

abnormality is cranial to heart base

Midline opacity on VD view

Congenital MegaesophagusCongenital Megaesophagus

Segmental–Vascular ring anomaly

R d d t h–Redundant esophagus

Generalized

–"Megaesophagus"

Vascular Ring AnomaliesVascular Ring Anomalies

More common in dogs

Arise from aortic arch or subclavian abnormalities

Patient may also have generalized megaesophagus

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Vascular Ring AnomaliesVascular Ring AnomaliesAssess the location of the compression

relative to the heart base. Always attempt to assess esophageal

motility caudal to the compression

Breeds predisposed to PRAAGerman Shepherd

Great DaneIrish Setter

P.R.A.A.P.R.A.A.

Aorta

Aorta

Normal

R R LL

MPA MPA

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Acquired segmental Acquired segmental megaesophagusmegaesophagus

Obstruction

– Foreign body

– Cicatrix

Tumor– Tumor

Esophageal DysfunctionEsophageal Dysfunction

Aspiration pneumonia is a common complication of esophageal dysfunction

An intense alveolar pattern, primarily in the ventral lung lobes (lung patterns next week)the ventral lung lobes (lung patterns next week)

Assess the lungs for evidence of aspiration with megaesophagus

Assess the esophagus when evidence of aspiration – megaesophagus may not be evident on surveys

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Swallowing DisordersSwallowing Disorders

Review Fluoroscopy movies- via http://radstudents.ncsu.edu

Folder = fluoroscopy moviesFolder = fluoroscopy movies

Sliding Hiatal HerniaSliding Hiatal HerniaSharpei

Brachycephalic breeds

Siamese

Often manifests in patients with partial upper airway obstruction

Sliding hiatal hernia

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Inspiration during laryngeal collapse

Inspiration after intubation

Larynx and bronchi Larynx and bronchi –– ensure you know ensure you know normal anatomynormal anatomy

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Mediastinum Mediastinum

Case DiscussionsCase Discussions

3/01/20113/01/2011

Case 1Case 1

6 year old Golden Retriever 60096 year old Golden Retriever 6009

Male castrate Male castrate

Poor exercise tolerance, collapses with minimal Poor exercise tolerance, collapses with minimal iiexercise exercise

Rattles when breathing Rattles when breathing

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Case 1 Findings Case 1 Findings

The esophagus is gas distended in all views The esophagus is gas distended in all views There is no evidence of inhalation pneumonia There is no evidence of inhalation pneumonia

Note the ventral deviation of the cranial intrathoracic Note the ventral deviation of the cranial intrathoracic trachea.trachea.

Dx: Generalized megaesophagus Dx: Generalized megaesophagus

What are some differentials for generalized megaesophagus?What are some differentials for generalized megaesophagus?

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Case 2Case 2

7 year old DSH7 year old DSH 7162471624

Male castrateMale castrate

Dyspnea, possible feline asthmaDyspnea, possible feline asthma

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Case 2 Findings Case 2 Findings

Pneumomediastinum, pneumoretroperitoneum and pneumothorax are Pneumomediastinum, pneumoretroperitoneum and pneumothorax are present.present.

A large amount of subcutaneous emphysema is present, predominantly A large amount of subcutaneous emphysema is present, predominantly located within the cervical and axillarylocated within the cervical and axillary soft tissues.soft tissues.

Th l l b h i fl t d i b l i f th l l i t thTh l l b h i fl t d i b l i f th l l i t th The lung lobes are hyperinflated, causing bulging of the pleural margins at the The lung lobes are hyperinflated, causing bulging of the pleural margins at the intercostal spaces and caudal displacement of the diaphragm.intercostal spaces and caudal displacement of the diaphragm.

The large amount of air in the thoracic cavity is resulting in caudal The large amount of air in the thoracic cavity is resulting in caudal displacement of the diaphragm as with tension pneumothorax, possibly displacement of the diaphragm as with tension pneumothorax, possibly exacerbated by pulmonary hyperinflation.exacerbated by pulmonary hyperinflation.

There is an alveolar pattern cranial to the cardiac silhouette on the lateral There is an alveolar pattern cranial to the cardiac silhouette on the lateral projections, likely secondary to recumbent atelectasis.projections, likely secondary to recumbent atelectasis. An endotracheal tube An endotracheal tube is present, presumably within the tracheal lumen.is present, presumably within the tracheal lumen.

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Case 3Case 3

8 year DLH8 year DLH 4895348953

Male castrate Male castrate

Recent weight lossRecent weight loss

Mass palpated on left kidney Mass palpated on left kidney

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Case 3 FindingsCase 3 Findings

There is an increase in soft tissue opacity caudal There is an increase in soft tissue opacity caudal to the cardiac silhouette that silhouettes with to the cardiac silhouette that silhouettes with both the diaphragm and the heart. There is poor both the diaphragm and the heart. There is poor distinction of the diaphragm at this level. distinction of the diaphragm at this level.

These findings are consistent with a peritoneal These findings are consistent with a peritoneal pericardial diaphragmatic hernia. pericardial diaphragmatic hernia.

How would you confirm this diagnosis?How would you confirm this diagnosis?

Case 4Case 4

10 year old Labrador Retriever 10 year old Labrador Retriever 8385783857

Female spayed Female spayed

Polydypsia and weight loss, non regenerative Polydypsia and weight loss, non regenerative anemia anemia

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Case 4 FindingsCase 4 Findings The trachea is dorsally displaced cranial to the heart by an ill The trachea is dorsally displaced cranial to the heart by an ill

defined soft tissue mass. defined soft tissue mass.

There is a soft tissue mass dorsal to the cranial sternebrae. There is a soft tissue mass dorsal to the cranial sternebrae.

The principal bronchi are displaced laterally and ventrally.The principal bronchi are displaced laterally and ventrally.

Findings are consistent with enlargement of the sternal, cranial Findings are consistent with enlargement of the sternal, cranial mediastinal and tracheobronchial lymph nodes. mediastinal and tracheobronchial lymph nodes.

The pulmonary parenchyma and cardiovascular structures are The pulmonary parenchyma and cardiovascular structures are within normal limits. within normal limits.

What are some differentials for thoracic lymphomegaly?What are some differentials for thoracic lymphomegaly?

Case 5Case 5

14 year old Siamese 14 year old Siamese

Male castrateMale castrate

Lethargy, anorexia Lethargy, anorexia

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Case 5 Findings Case 5 Findings

In lateral views there is an illIn lateral views there is an ill--defined soft tissue defined soft tissue and gas mass effect in the caudodorsal aspect of and gas mass effect in the caudodorsal aspect of the thorax. This is not apparent VD or DV the thorax. This is not apparent VD or DV views and is most consistent with a hiatal herniaviews and is most consistent with a hiatal herniaviews and is most consistent with a hiatal hernia. views and is most consistent with a hiatal hernia.

No other abnormalities are identified.No other abnormalities are identified.

Case 6 Case 6

9 year old Greyhound 9 year old Greyhound 6894468944

Male castrateMale castrate

Vomiting and diarrhea for 3 days Vomiting and diarrhea for 3 days

History of LSAHistory of LSA

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Case 6 Findings Case 6 Findings

There is gas dissecting around mediastinal There is gas dissecting around mediastinal structures indicating pneumomediastinum, structures indicating pneumomediastinum, possibly due to jugular venipuncture. possibly due to jugular venipuncture.

Residual barium persists in the peritoneal space, Residual barium persists in the peritoneal space, presumed cisterna chyli, and within the sternal presumed cisterna chyli, and within the sternal lymph nodes. lymph nodes.