Equine Throat/Thorax

Question 1

Clinical significance

Answer 1

Imaging is important in the evaluation of the equine airway and thorax

radiography and endoscopy are complementary
Large emphasis on equine medicine that focuses athletics
Specifically on the airway
decreased time = bigger benefits- $$

Question 2

Radiography

Answer 2

still image

morphologic abnormalities

Question 3

Endoscopy

Answer 3

Morphologic and functional abnormalities

Question 4

Preparation and safety

Answer 4

equipment

restraint

Question 5

Physical restraint

Answer 5

halter-radiolucent

+/- stocks

Question 6

Chemical restraint

Answer 6

xylazine- may cause head twitching, whihc can cause blurry image
detomidine
+/- opioid
Sedation= decreased muscle tone- can confuse endoscopic exam results

Question 7

Radiation safety

Answer 7

aprons
gloves
thyroid protectors

Question 8

Positioning for throat radiograph

Answer 8

lateral view= most common

center of plate over throat

Question 9

Epiglottis

Answer 9

should always be sitting on top of soft palate

horses are nasal breathers

Question 10

Endoscopy- throat

at rest

Answer 10

good for initial evaluation
ideally w/o sedation
because there would be muscle relaxation with it

Question 11

Endoscopy- throat

after exercise

Answer 11

increased respiratory effort

some airway dz occurs only during exercise

Question 12

Endoscopy- throat

during exercise

Answer 12

dynamic exam of the airway
treadmill
overland/dynamic endoscopy

Question 13

Placement of the endoscope

Answer 13

ventral meatus

advance to the nasopharynx

Question 14

Normal larynx anatomy

Answer 14

symmetrical arytenoid cartilages
opening to airway
vocal cord
guttural pouch opening
epiglottis- should have scalloped edge and should see vascularization over it

Question 15

Endoscopy-guttural pouch

Answer 15

using instrument to hold flap open

to put scope into guttural pouch

Question 16

ultrasonography

Answer 16

not as common as endoscopy and radiography for pharynx and larynx
equipment typically available in practive
non invasive
requires experience
Linear or curvilinear transducer
8-10 MHz
Transducer placed lateral

Question 17

Computed Tomography

Answer 17

CT
limited availability
may require general anesthesia
more assistance
more money
more common for skull and neck

Question 18

Radiographic signs- laryngeal disease

Answer 18

epiglottis position relative to soft palate
epiglottic thickening
epiglottic margination
malposition or malformed aryepiglottic folds
gas or mineralization in or around the pharynx
hyoid apparatus (bone)

Question 19

radiographic lesions- epiglottis

Answer 19

acute inflammation
may increase size of epiglottis
trauma-secondary to naso-tracheal intubation- common cause

Question 20

Masses of the epiglottis

Answer 20

medium to large
subepiglottic, epiglottic and para-epiglottic
Displacement of epiglottis
DDX: cyst, granuloma, abscess, rarely neoplasia

Question 21

Epiglottic entrapment

Answer 21

entraped in aryepiglottic fold
may or may not be detectable radiograpically
causes: decreased epiglottic size, altered shape and positioning- relative to soft palate
no scalloped edge or vascularization

Question 22

dorsal displacement of the soft palate

Answer 22

may be intermittent in normal horses- may induce with sedation or anesthesia - sounds like snoring 
consider abnormal until proven otherwise
Etiologies include: 
epiglotic hypoplasia
persistent epiglottic frenulum
epiglottic scaring or entrapment
palatal hypoplasia 
may be linked with other airway disease

Question 23

Arytenoid chondritis

Answer 23

performance-limiting upper airway disease
etiology-unknown
mucosal trauma with secondary viral or bacterial infection

horse will have difficulty breathing and have an abnormal upper resp noise
likely exercise intolerant

Question 24

Radiographic lesions- pharynx

Answer 24

radiographic signs: decreased gas content
alteration in size and contour
changes in size, shape, position of soft palate
diseases that result in reduced pharyngeal volume:
-trauma- fractures, foreign bodies
-retropharyngeal abscess
-retropharyngeal lymphadenopathy

Question 25

Palatal cyst

Answer 25

second to persistent dorsal displacement

Question 26

retropharyngeal abscess

Answer 26

significant narrowing of the pharynx
pushes guttural pouch dorsal
strep equi common cause 40%

Question 27

Guttural pouch disease

Answer 27

increase or decrease in air content
increased soft tissue/fluid opacity
deformity
intraluminal mass
pharyngeal compression 
displacement of the larynx and or trachea

Question 28

Guttural pouch tympany

Answer 28

several gaseous distention
foals
often unilateral
compresses the pharynx
displaces the larynx and trachea ventrally
etiology unknown
-congenital abnormality creating mucosal flap acting as a one way valve 
soft on palpation (abscess feels firm)

Question 29

Guttural pouch effusions

Answer 29

fluid/gas interfaces- standing horizontal beam radiography
hemorrhage (mycosis)
exudates (empyema)- strep equi
less likely causes- other bacterial infections; ruptured retropharyngeal abscess; regional trauma or penetrating foreign body
unilateral-commonly

Question 30

Chondroids

Answer 30

intraluminal masses
inspissated pus
chronic strep equi infection
must be large enough and surrounded by air to be detected

Question 31

Temporohydoid osteoarthopathy

Answer 31

middle ear disease
Dz of temporohyoid joint- stylohyoid and petrous temporal bones
etiology unknown
-infection of inflammation spreading from nearby structures
-such as the inner ear or guttural pouch

Question 32

Guttural pouch mycosis

Answer 32

life threatening dz
ticking time bomb
first signs- epistaxis, CN signs
little radiographic evidence
many important structures

Question 33

Dx imaging- equine thorax

Answer 33

not as common in horses compared to SA
limited due to size-lose detail with mass
foals=1-2 cassettes to obtain a lateral view
adults= 3-4 cassettes to obtain a lateral view - heart always in image as a reference point
Detail in adult patient is optimized by place in the lesion closer to the cassette
adult horse is limited to the lateral view
limitations with portable equipment
-cassette size
-generator power

Question 34

Thoracic ultrasonography- thorax

Answer 34

ideally examination area clipped
no 40 clipper blade
size of clipped area-based on the auscultation findings, enlarged as needed
excellent tool for:
locating fluid pockets
guiding a needle for a dx sample
assessment of pleural thickening
fibrin deposition or adhesion formation 
area of U/S=area of auscultation