Surgical respiratory tract diseases - Equine 1 & 2 Flashcards
List some primary problems of the equine URT - 6
- nasal discharge
- exercise intolerance/poor athletic performance
- abnormal respiratory noise (stridor and stertor)
- epistaxis
- abnormal swelling of head/neck
- cough
Outline the workup for equine URT disease
- signalment
- hx (past and current)
- PE and URT exam
- examination at work
- special examinations
- (examination of LRT depending on ultimate diagnosis)
What should you examine on the URT?
- nasal discharge
- facial symmetry
- airflow (symmetry)
What should you palpate when examining the URT?
- nostrils
- nasal septum
- sinuses
- GP
- regional LNs
- larynx
- trachea
What should you percuss when examining the URT?
Paranasal sinuses (frontal and maxillary)
What should you look for when examining a horse at work? 4
- onset and character of abnormal noise
- exercise tolerance
- soundness
- respiratory pattern and recovery
What special examinations can be performed on the URT? 5
- endoscopy (common, easy)
- radiography, CT scan
- sinoscopy
- bacterial culture/ sensitivity (relatively unhelpful)
- biopsy for cytology/ histopatholgoy
What dynamic exams can be done when examining a horse URT? 5
- endoscopy at high speeds
- (measurement of airway pressures)
- exercising ECG
- lameness assessment
- standardised exercise trial (fitness and myopathy assessment)
How should nasal discharge be defined? 3
CHARACTER - serous, mucoid, purulent, necrotic
LATERALITY - unilateral (sinuses, nasal passage, GP), bilateral (lungs, pharynx)
ODOUR - none (LRT disease, sinusitis, pharyngitis, pouch empyema) or foul odour (dental disease, neoplasia, necrotising LRT disease)
List 5 possible sources of nasal discharge
- nasal passages
- paranasal sinuses
- GPs
- pharynx/larynx
- LRT
How do you determine the source of a discharge? 3
Follow the trail of a discharge:
- PE
- Endoscopy - paranasal sinuses, GPs, LRT
- Radiography - sinuses, GP
How common is primary nasal passage disease?
Uncommon (in UK)
Causes of primary nasal passage disease - 4
- Bacterial infection of septum or turbinates
- Fungal infection of septum or turbinates
- neoplasia
- FBs
What findings might suggest nasal discharge is due to sinusitis? 5
- PE: decreased resonance on percussion
- ENDOSCOPY: drainage from nasomaxillary opening
- RADIOGRAPH (oblique): fluid lines, mass
- CT
- SINUS CENTESIS: rule out S.equi
Causes - nasal discharge due to sinusitis - 4
- Dental disease * (09-11, M1, M2 M3)
- Bacterial infection
- Fungal infection
- Neoplasia
What might be concurrent findings with nasal discharge due to sinusitis? 3
- decreased airflow
- facial swelling
- dullness on percussion
Tx - sinusitis
MEDICAL - lavage and ABs
SURGERY - sinoscopy (including fenestration of the ventral conchal bulla, VCB), removal of inciting cause (e.g. tooth), flap sinusotomy
What is the most common way to access to sinus for sinoscopy?
Concho frontal sinus approach in most cases and fenestrate the VCB if necessary to access the rostral compartments.
T/F: sinoscopy can be performed in the standing horse
True
What are the causes of nasal discharge due to GP disease? 4
- GP empyema * bacterial infection of GP, often S.equi
- GP catarrah = excessive mucous production by pouch due to inflammation
- (GP mycosis)
- (GP neoplasia)
What are possible concurrent signs of nasal discharge due to GP disease? 2
- swelling at Viborg’s triangle
- other signs of GP mycosis
What are the 3 borders of Viborg’s triangle?
between tendon mandibularis, linguofacial vein and back of the mandible. Viborg’s triangle sits directly over the GP. Becomes swollen in GP empyema.
Dx - GP empyema - 4
- ENDOSCOPY (discharge or fluid accumulation in the pouch)
- RADIOGRAPHY (fluid line)
- chondroids (inspissated pus)
- culture
Tx - GP empyema - 2
MEDICAL - pouch lavage, AB, removal of chondroids (before lavage)
SURGERY - viborg’s triangle approach for drainage, ventral paramedian approach for chondroid removal, dyspnoeic horses may require tracheostomy
What are the main causes of abnormal respiratory noise/ poor performance?
PHARYNX: DDSP, postural compression (nasopharyngeal collapse), pharyngeal cysts
LARYNX: RLN, AAE, arytenoid chondroitis
What causes an abnormal noise?
Turbulent flow (2 conditions for this - flow and decreased lumen size/obstruction)
Outline resistance in the airway
INSPIRATION: resistance is predominantly in the URT
EXPIRATION: resistance is predominantly in the lung
Poiseuille’s law: resistance is inversely proportional to teh 4th power of the radius of the airway
How can you refine the problem of URT obstruction causing abnormal noise? 3
- CONSTANCY - Fixed (mass lesions, chondritis, strictures), dynamic (RLN, DDSP, AEE)
- QUALITY - stridor (narrowed airway - RLN, chondritis, mass lesions, strictures), stertor (tissue vibration - DDSP, nostril problems)
- PHASE - inspiratory (RLN), expiratory (DDSP, AEE), both (mass lesions, chondritis)
What are the different sites of URT obstruction? 5
- NOSTRILS - alar fold collapse/flutter, incomplete dilation of the nares
- NASAL PASSAGES - septal disease, small nasal passages, eruption bumps (tubercula transitoria), mass lesions
- SINUSES (expansile lesions) - cysts, mass lesions
- PHARYNX - DDSP, postural compression, pharyngeal cysts
- LARYNX - RLN/ roaring, epiglottic entrapment, arytenoid chondritis
Describe the anatomic basis of DDSP
- normally the palate is buttoned onto the larynx forming an airtight seal. Free border of palate is under epiglottis –> obligate nasal breather
- In DDSP, the free border of the palate moves dorsal to the epiglottis during exercise –> functional obstruction (decreased CSA of nasopharynx and increased resistance to airflow).
CS - DDSP
‘choking down’ = expiratory noise (stertor),
- decreased athletic performance
- mouth breathing (pathognomic)
Dx - DDSP
- Gold standard = dynamic endoscopy*
- Difficult at rest
- Typical hx (normal at rest)
- Rule out other URT disorders
- Assess GPs (inflammation, exudation and retropharyngeal lymphadenopathy)
DDSP suspected if:
- horse readily displaces with nasal occlusion and doesn’t easily replace palate
- there is marked hypoplasia or deformity of the epiglottis
What are the 2 broad treatment options for DDSP?
Conservative and surgical
Outline conservative tx of DDSP
- Treat concurrent disorders (GP or LRT disease)
- Minimise poll flexion
- Keep mouth closed
- Tongue-tie
- The Cornell Collar (mimics function of TH mm)
Outline surgical treatment of DDSP
- Numerous procedures described (aetiology not well understood)
- Llewelyn procedure: sternothyrideus myectomy +/- staphylectomy (trim edge of palate)
- Thermal palatoplasty (thermal or cautery) - stiffen soft palate to prevent billowing, surgical tension palatoplasty with similar concept
- Laryngeal ‘tie-forward’ (Cornell) - placement of a prosthetic suture to mimic function of thyrohyoideus mm)
Name 3 different sites of pharyngeal cysts
- Subepiglottic (thyroglossal duct)
- Dorsal pharyngeal (craniopharyngeal duct)
- Palatine
CS - pharyngeal cysts?
Foals versus young adults
- FOALS - dysphagia, dyspnoea
- YOUNG ADULTS - poor performance, respiratory noise
Cause - Recurrent laryngeal neuropathy (RLN)
due to degenerative axonopathy of the recurrent laryngeal nerve. left side affected. most common in large stature horses. The result is the impaired function of the cricoarytenoideus dorsalis muscle (CAD mm), the primary abductor of the arytenoid cartilage.
RLN - CS
- asymptomatic (rest and low levels of exercise)
- inspiratory stridor (moderate to marked exercise)
- impaired athletic performance (high exercise)