Diseases Of The Ear Flashcards
Otitis externa - definition and occurance
- Acute or chronic inflammation of the external ear canal
- Prevalence: 15-20% (dogs), 6-7% (cats)
- Affects one third of patients
What is the etiology of otitis externa?
- I. Primary factors
- II. Secondary factors
- III. Predisposing factors
- IV. Perpetuating factors
Primary factors
Diseases that cause OE directly, such as:
(90% due to allergy - skin covered tube!!)
• Atopy
• Food allergy
• Contact - hypersensitivity
• Parasites (otodectes, demodex, sarcoptes, etc)
• Foreign Bodies
• Disorders of keratinization
• Autoimmune disorders
• Endocrine disorders (hypothyroidisim)
• Tumors
Secundary factors
Do not cause problems in a healthy ear, but can cause problems in case of primary/predisposing factors (eg. Inflammation turn purulent)
• Bacteria
• Yeasts
• Irritative substances
• Overcleaning
–> Only treating these wont cure if underlying condition helping the overgrowth
Predisposing factors
Factors that alter the externa ear canal, thus make it susceptible for OE - preventing self cleaning!
• Pendulous/naturally narrowed (chow chow, pug) auditory canal
• Frequent bathing, swimming (humid - infection)
• Increased soft tissue content (glandular hyperplasia)
• Increased amount of hair within the ear canal (Blocking epith migration, incr temp)
Perpetuating factors
Consequences of OE that maintain inflammation - must treat to as they maintain!!!
• Skin edema, fibrosis (diameter)
• Reduced epithelial migration (Ear cells act like threadmill slowly tp everything outwards, If not poroper - debris build up)
• Ulceration, thickened skin
• Ceruminous gland dilatation and obstruction • Stricture
• Otitis Media (OM) (Eg pseudomonas migrate through tymp memb -> colonize in middle ear. Can also travel outwards)
What are the most important diagnostic steps of otitis externa?
For successful treatment all must be fullfilled!!!
• First: Precise diagnosis
• Signalment + History -> Primary and predisposing
factors (food, localization of scratching - systemic derm?, FB, other animal, behaviour)
•Thorough otoscope examination of the external ear canal to evaluate six key points (see on next card)
•Additional examinations to uncover actual problems (cytology!!!!, microbiology, histopathology)
What are the 6 points you have to assess during the otoscopic examination?
- Skin of concave surface of the pinna
- Width and length of ear canal
- Amount and quality of discharge
- Skin of ear canal
- Sensitivity and palpation of the ear canal (nonsensitive terrible looking irreversible, resection?)
- State of tympanic membrane (Obscured by hair, discharge etc
Good way to check intactness wo visualization - fill with water, no bubbles/leaking = Intact!)
Why is cleaning so important?
• Important to evaluate some of the former parameters
• Very useful in treatment (incr surface area for medication to work)
• First thing after/during examination of
the ear canal
• Client education (do it in front of owner!)
How do you clean?
•If a thorough cleaning is not possible without it, sedation is necessary - must schedule later appointment
•Mechanical cleaning -> Warm (lukewarm) saline infusion, tapwater in great quantities until all content is removed
- (cold touch TM -> caloric? Effect -> ataxia etc suddenly, traumatic for owner)
- avoid eyes!
- mostly work of the owner, regularily! (Weekly eg, all depending)
What do you use for cleaning when water/saline isnt enough?
- Cerumenolytics
- drying agents
- disinfectants
Cerumenolytics
- Mainly for waxy/lipid containing contents. Contain ingredients that emulgeate wax and lipids, such as Dioctil Sodium (DSS), Calcium Sulphosuccinate, squalene and glycerin
• SQUALENE - Not ototoxic, no worries if rupture of tymp - also not more expensive, less effective etc, so use it!!!
Drying agents
When very maceratied wet ears, drying out ear properly important!
Lower the pH of the ear, cause ceratolysis, and slight antimicrobial effect.
• Boric acid, salicylic acid, benzoic acid, acetic acid, lactic acid
Disinfectants
Damage of microbes - purulent ears important
They potentiate the effect of antimicrobials by destroying bacterial cell wall, lowering resistance, and dissolving biofilm.
• Chlorhexidine, tris EDTA
• Chlorhexidine is available in multiple concentrations. The higher the cc the more effective, and more irritative chlorhexidine is (Middle Ear!) use LOWER conc!!!!
What are the steps of approching otitis externa?
Step by step
- : History
- : Examining the ear
- : Otoscopic examination
- : Cleaning
- : Repeated otoscopic examination, evaluating cleaning, further cleaning if necessary
- : Sampling
- : Sending the patient home with preliminary treatment
- : Modifying treatment based on progress (Control)
Treatment of otitis externa - overview of possibilities
• Cleaning is enough on its own • Specific treatment - Antibiotics - Antimicotics - Antiparasitics • Anti-inflammatory drugs • Diet (allergy - atopic dermatitis)
Sampling
- cytology is best sample, shows everything we need to know!!
- microbio may be misleading - normal flora of ear
- problem - treat, no problem - dont treat!
Topical or systemic treatment?
- Topical: Very beneficial in case of non ototoxic materials, as topical concentration is a lot higher(!!!), and can break through antibiotic resistance. Available drugs choice is limited in case of a perforated TM.
- Systemic: Beneficial in middle ear involvement, but reaches the ear in very low concentration + side effects (Not always possible - dog wont let you do it - systemic sometimes only option)
- Decision should be on a case by case basis
What happens with an untreated OE?
OE IS A PROGESSIVE DISEASE!
• Untreated acute otitis externa (OE) can progress into chronic OE
- Sebaceous gland hyperplasia
- Epithel hyperplasia
- Hyperkeratosis
- Ceruminous gland hyperplasia
- Follicular hyperplasia
- Ceruminous glands dilate > Cerumen production increases > Increased humidity and pH, lowered lipid concentration of cerumen
- Long term effect: Apocrine gland rupture, sebaceous gland degeneration, auditory canal fibrosis, stricture, calcification
–> may turn irreversible - resection surgery!
Name the 5 most common causes of OE
90% of cases its one of these! • Bacterial otitis externa • Malesseziosis • Parasitic otitis externa • Foreign bodies • Masses
Bacterial OE
Secondary, requiring primary: - Allergy - Foreign body or predisposing factors: - Too much hair - Water in the ear
Bacterial OE agents
🔺Part of flora - can mult fast if predisposing, already there!
• Staphylococci: Part of the flora of the healthy ear canal
• Streptococci: Also part of healthy ear flora, except for ß hemolyzing
🔺Not in flora:
• Pseudomonas (Not part of ear flora in this climate - tropical!)
Hard to rid of, multires, but on its own we can treat eventually. From ground dog can scratch into ear.
Cononizers, rare:
• Escherichia Coli
• Enterobacteriaceae
• Proteus
Bacterial anamnesis/ how can you recognize bacterial OE?
- Patient shows signs of OE (pain, scratching)
- Ear starts to stink, unique smell
- Purulent discharge in neglected cases
- Common in dogs, extremely rare in cats (if pus in cat, probably polyp!)