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Canine otitis externa - Coggle Diagram

- - - - Conformation
        
        pendulous pinnae
        
        hair or stenotic canals
        
        long, steeply sloping canals
      - Maceration
        
        swimming
        
        environmental temperature (high)
        
        high humidity
      - Trauma
        
        inappropriate cleaning
      - errors in otic pharmacy/ management of ear disease
        
        E.g. need to shake bottles if in suspension, may need to dispense 1ml syringe to ensure correct amount deposited into ear
      - concurrent disease
        
        e.g. pyrexia
      - Tumours, polyps, cysts
        
        otic neoplasia
        
        nasal-pharyngeal polyp
        
        obstructs the ear canal
        
        rarely tumours adjacent to ears may compress or invade the ear canals and middle ears
  - - - Foreign bodies, tumours, polyps
        
        e.g. grass awns
      - Ectoparasites
        
        otodectes
        
        otodectes cynotis infection has characteristic appearance
        
        large amounts of dry, dark brown, waxy debris with variable amounts of inflammation
        
        may visualise mites upon otoscopic examination or scrapes under microscope
        
        some respond to acaricdal treatment, even though no mites can be found
        
        demodex
        
        Neotrombicula
        
        ticks
      - certain infections
        
        dermatophytosis (rare)
        
        BIOFILM
        
        e.g. produced by staphylococcus epidermis, pseudomonas aeruginosa
        
        N-acetylcysteine
        
        bacterial infection
        
        staphylococcus spp
        
        streptococcus spp
        
        proteus spp.
        
        high yellow exudate, discharge becomes darker in concomitant wax production
        
        pseudomonas spp.
        
        often found in ears that are v painful, inflamed, eroded or ulcerated
        
        copious amounts of bright yellow-green, foul-smelling exudate
        
        often chronic cases, but acute suppurative otitis due to this is not uncommon
      - Hypersensitivities
        
        atopic dermatitis
        
        cutaneous food reactions
        
        contact
        
        most common triggers for recurrent otitis in dogs
        
        ears commonly affected in allergy and sometimes the only affected area
        
        with otitis in allergy there is a tendency for chronicity and for infection
      - Disorders of keratisation
        
        often associated with chronic otitis externa
        
        breed predisposition (often accompanied by narrow, hirsute ear canals)
        
        e.g. cocker spaniels
      - autoimmune conditions
        
        may be associated with pustules and crusts on the pinnae and otic epithelium
        
        pemphigus foliaceus
        
        may cause ulceration in ear canal
        
        associated with lesions elsewhere and systemic ear disease
      - contact reactions to ear cleaners and medications
      - hypothyroidism, hyperadrenocorticism and sex hormone dermatosis which can give rise to immunologic and cutaneous changes
  - - - S. (pseudo)intermedius
      - pseudomonas
      - Proteus
      - Klebsiella
      - E.coli
      - Others
  - - - Changes in microflora leading to overgrowth and infection
        
        staphylococcal
        
        malassezia
        
        often chocolate-brown waxy discharge
      - Otitis media
        
        Often unrecognised
        
        infection in bullae -> reservoir for relapse and continued signs
        
        infection may persist despite healed tympanic membrane
        
        other pathology
        
        neoplasia
        
        polyp
        
        cholsteatoma
        
        Primary secretary otitis media (PSOM)
        
        cavalier king charles spaniel (most 3-7yrs)
        
        pain, near signs, pruritic, otitis externa, impaired hearing
        
        Clinical signs
        
        subclinical
        
        facial nerve damage
        
        drooping ear/lip
        
        dribbling, head tilt
        
        pain, deficient palpebral reflex
        
        Horner's syndrome
        
        miosis
        
        ptosis
        
        enophthalmos
        
        prolapsed nictitating membrane
        
        systemic illness
        
        Otitis interna
        
        lack of orientation
        
        nystagmus
        
        ataxia
        
        circling
        
        pain
        
        vomiting
        
        MUST BE REVERSED
        
        Myringotomy
        
        repeated flushing
        
        expensive
        
        surgery
      - Progressive chronic pathologic changes in otic epithelium and underlying cartilage
        
        ulceration
        
        glandular hypertrophy/stenosis
        
        (hyperplasia of the apocrine glands)
        
        thickened, folded canals
        
        MUST BE REVERSED
        
        Topical glucocorticoids
        
        Oral glucocorticoids
        
        Oral ciclosporin
        
        reduction of effective diameter of ear canal
        
        decreased epidermal cell migration
        
        increased humidity within the canal lumen
        
        in severe chronic cases
        
        chronic fibrosis
        
        ossification of external ear canal and associated cartilage
- - - - neoplasia or polyp
    - - otodectic mange
  - - - normal tympanum should be translucent with radiating stria
- - - - leukocytes
        
        neutrophils
        
        contact reactions
        
        degenerate neutrophils with intracellular bacteria seen in lots of infections
        
        present in ulceration along with RBCs
      - squames +/- acanthocytes
      - neoplastic cells
      - yeast
        
        peanut shape indicates malasezzia
      - bacteria
        
        cocci
        
        indicates staphylococci or streptococci
        
        G-ve Rods
        
        indicates pseudomonas or proteus
  - - - views
        
        dorsoventral skull
        
        left and right lateral obliques
        
        open mouth rostrocaudal (under GA)
      - Occlusion and bony change in ear canals
      - soft tissue opacity of middle ear cavity
      - lysis/proliferation of bulla wall
      - osseous changes should prompt a consideration of surgery
    - - detect fluid and soft tissue within tympanic bullae
- - - - massage for 1-2 min to loosen and dissolve the debris
        
        wipe with cotton wool and repeat until solution clear of exudate/debris
  - - - higher dose of ketamine is preferred as provides better restraint for about 20 minutes
  - - - if animal swallows/gags/coughs when fluid placed in ear this is a good indication that TM is ruptured
      - if this is unable to rinse away exudate/debris
        
        solution containing propylene glycol, malic acid, benzoic acid and salicylic acid can be used
        
        epic-otic (virbac) has also been used without apparent signs of ototoxicity
        
        always flush middle ear after with saline
      - NOTE: there is no completely safe solution for cleaning middle ear. Even water may cause loss of cochlear and vestibular function
  - - - neomycin
      - gentamicin
      - polymyxin b
        
        bactericidal
        
        alteration of cytoplasmic membrane permeability
        
        ototoxic
        
        inactivated by cellular debris, so association with ear cleaning important
      - fusidic acid
        
        bacteriostatic
        
        interference with bacterial protein synthesis
    - - topical preparation containing one of the penicillins or c+s
    - - gentamicin
      - polymyxin B
        
        evidence that this and miconazole have synergistic activity v staphylococci and pseudomonas
      - enrofloxacin
      - amikacin sulfate
      - Tobramycin injectable
      - ciprofloxacin
      - clavulanate potentiated ticarcillin
      - ofloxacin
      - marbofloxacin
      - ceftazidime
    - - clotrimazole
      - miconazole
      - cuprimyxin
      - nystatin
      - amphotericin B
    - - glucocorticoids
        
        reduce pruritis, swelling, exudation and tissue hyper proliferation
        
        long term use of topical glucocorticoids can result in systemic absorption
        
        elevation of liver enzymes
        
        suppression of the adrenal response to adrenocorticotropic hormone
    - - Polyvinyl acetate
        
        soaked with an antibiotic + trizEDTA
      - alternative to repeated topical treatments
      - inserted into ear canal under GA
      - absorb discharge, draw antibiotic solution into the ear canal and act as a reservoir
      - steroid soaked wicks can be effective in resolving stenosis
        
        also help prevent cicatricial stenosis following surgery to remove polyps and other masses in ear canal
    - - e.g. o.cyanotis infection
      - systemic acaricides
        
        ivermectin
        
        selamectin
        
        moxidectin
        
        fipronil
      - all contact animals should be treated as asymptomatic carriers as they may be a source of reinfection
      - use of systemic treatments ensures O.cynotis on other body areas also killed
  - - - prednisolone/methyprednisolone
      - 10-14d
      - reduce severe inflammation and swelling due to hypersensitivity states or foreign body reaction that occurs due to rupture of cystic apocrine glands
        
        reduce stenosis
        
        reduce oedema
        
        reduce hyperplasia
        
        allow otoscopic examination and allow a better cleaning process
    - - when TM ruptured and infection present in middle ear
        
        middle ear (tympanic bulla) contains highly vascular mucous membrane lining, so drugs may diffuse better here than external canal.
        
        antibiotics recognised effective for treatment of otitis media
        
        c+s
        
        Enrofloxacin 5-20mg/Kg once daily
        
        Marbofloxacin 2-5mg/Kg once daily
        
        Ciprofloxacin (off label) 10-20mg/Kg once daily
        
        Orbifloxacin 2.5mg/Kg once daily
        
        Cefalexin 20-30mg/Kg twice daily
        
        In case of multi-resistance
        
        Ceftazidime (off label) 30mg/Kg four times daily
        
        Ticarcillin (off label) 40-80mg/Kg three times daily
        
        Meropem (off label) 8mg/Kg twice daily
      - when poor response to topical treatment
      - choice based off c+s
      - unless ear canal epithelium eroded/ulcerated extensively systemic ABs unlikely to achieve therapeutic concentrations within fluid and waxy exudates of the external canals in which the infectious organisms are harboured
        
        thus systemic abs also indicated in cases of stenosis, ulcerations and deep infections
    - - cases of otitis media cause by Malassezia spp or when topical therapy not an option
      - drugs used include
        
        Ketoconazole (off label) 10mg/Kg once daily
        
        Itraconazole (off label) 5mg/Kg once daily
        
        Fluconazole (off label) 2.5-5mg/Kg once daily
  - - - seborrheic ears
      - hirsute ears
      - stenotic ears
      - pendulous ears
      - purulent discharge
    - - ceruminolytics, surfactants and foaming agents
        
        e.g. sodium docusate
      - astringents or drying agents.g. isopropyl alcohol
      - antimicrobial agents
        
        parachlorometaxylenol (PCMX)
  - - - when entire external ear +/- middle ear need thorough cleaning
    - - avoid fluids running from ear into respiratory tract through the Eustachian tube
    - - video otoscope
      - urinary catheter
      - feeding tube connected to a syringe and sterile saline, preferably through a 3 way tap
  - - - suspected or confirmed otitis media
      - samples required for cytology and culture from tympanic bulla
      - allow flushing of middle ear cavities
- - - - endstage otitis externa
      - persistent otitis after LWR or VCA
      - otitis media
      - para-aural abscess
      - horizontal canal neoplasia
        
        ceruminous gland adenocarcinoma
        
        squamous cell carcinoma
      - severe ear canal trauma
    - - deafness
      - facial nerve paralysis
      - vestibular disease
      - haemorrhage
      - wound breakdown
      - fistula/sinus formation
      - avascular necrosis of pinna
  - - - horners syndrome (more common in cats)
      - facial nerve paralysis (less than with TECA/LBO)
      - Vestibular syndrome
      - Recurrence of polyps
      - hypoglossal nerve damage