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Examination Procedure
In the following photographs the dog is positioned
in lateral recumbancy with the nose pointed to the right of the screen and dorsal at the
top of the image. To better orient you, some images have a close-up image to the right of
a larger field view of the same image.
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Few dogs or cats will allow a
thorough examination of the ear canals while awake. Heavy sedation or general anesthesia
are usually required in order to perform a thorough examination and ear cleaning.
The animal should be
positioned in lateral recumbancy |
Indications for otoscopic exam include:
- ear scratching/ rubbing
- head shaking
- ear odor
- discharge, redness or swelling of the ear
- hair loss around the ears
- signs of facial nerve paralysis indicating middle ear
disease
- deafness
- head tilt indicating middle ear disease
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The ear has the following
components:
- pinna (helix) which is the flap of the ear
- the external ear canal which has a vertical component and a
horizontal component
- the ear drum (tympanic membrane)
- the typanic bulla (middle ear) which is normally filled with
air
- the inner ear (represented simply by the gray oval)
The external ear canal is surrounded by the auricular
cartilage which limits its distensibilty.
The external ear canal is lined by pink, mostly hairless
tissue.
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| The external flap of the ear is called the
pinna or helix. Breeds with upright (prick ear) pinnae have fewer ear problems that
breeds with heavy pendulous ears (like Cocker Spaniels). There is a greater airflow
in an upright ear canal, which prevents moisture from building up in the ear canal. A
moist ear is more susceptible to infection. Both the
external and internal aspects of the pinnae should be examined. The external pinnae are
usually haired. If the ear is pruritic, scratching may result in hair loss on the pinnae
or at the base of the ear. Severe scratching may also lead to excoriation of the skin of
the ear and/or tears at the ear margins. There are some ear diseases that result in loss
of hair from the pinnae in the absence of pruritis. For example, Daschund dogs may develop
a non pruritic alopecia of the pinnae.
The inner side of the pinnae are less haired than the
external aspect. Breeds vary in the amount of hair they have on the inner aspect of the
pinnae. Poodles often have very hairy ears while Boxer's ears have minimal hair on the
inside of the pinnae. Animals with hairy ears will have reduced air flow in the ear canal
are are predisposed to infection.
The inside of the pinnae should be examined for redness,
discharge and excoriation. |
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If the ear is infected but
discharge is not visible, the infection can often be detected by smelling the ear. I
always smell the ear canal of awake dogs and cats as part of a routine physical
examination. |
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To align the
horizontal and vertical portions of the ear canal and provide for a straight path to view
the eardrum, firmly pull the pinnae away from the head in a dorsal direction and away from
the head. In this picture the ear is being pulled toward the top of the screen, and toward
you. Maintain traction on the pinnae as you examine the ear canal. |
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The otoscope is
inserted into the ear canal while maintaining traction on the pinnae to keep the
horizontal and vertical parts of the ear canal aligned. If you have not already viewed the
section on equipment (otosope heads and cones) you are encouraged to do so.
(equipment) I am right-handed and use my left hand to pull
the ear flap and my right hand to hold the otoscope.
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The color and health of the ear
canal should be assessed as well as characterizing the color and consistency of any
discharge. A small amount of brown ear wax (cerumen) and a small amount of hair can be
normal if the ear has a normal odor and the ear canal is pink and healthy. The ear
canal narrows as you approach the ear drum but you should make an assessment of whether
the ear canal is more narrow than expected for the size of the animal. This assessment
will require experience looking at the ear canals of a wide variety of breeds.
Narrowing of the ear canal can be due to fibrosis (stenosis) as a consequence of chronic
infection or may be a breed variant (for example Sharpei dogs often have very narrow ear
canals.
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The ear drum (tympanic membrane) can be
visualized in the distance as a semi transparent, smooth, light gray membrane (often
called a "pearly gray"). You may need to rotate the otoscope and cone to see 360
degrees around the membrane. The surface is flat or slightly concave. A bulging
(convex surface) of the ear drum may be observed if fluid is accumulating in the middle
ear. You may see yellow fluid (pus) in the middle ear in animals with middle ear
infections.
If you cannot see the ear drum consider the following
possible reasons:
- the ear flap is not pulled tight to straighten the ear canal
and the tip of the cone is pressed against the wall of the ear canal
- the ear cone is too short and the ear drum is too far in the
distance to see
- the ear canal is stenotic and the cone cannot be inserted
far enough to see the ear drum
- debris (exudate or foreign material) is obscuring
visualization
- the ear drum is ruptured. Sometimes you can actually see
ragged edges of tissue where the ear drum used to be but more often you just see a
"black hole" where the ear drum use to be.
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Obtaining diagnostic samples and cleaning the ears
After examining the ear with a high magnification lens, I
change the otoscope head to one that provides less magnification but which allows an open
channel through which to pass instruments.
(see
otoscope heads)
Before instilling anything into the ear, diagnostic samples
should be collected. The ears may be sampled using a bacteriologic culturette for
bacterial culture and a swab can be obtained using a cotton tipped applicator for
cytology, searching for yeast, neoplastic cells, bacteria and mites. These swabs can be
passed through the otoscope cone to obtain samples or the swabs can be passed blindly into
the ear canal with minimal pressure to avoid inadvertent rupture of the ear drum.
| In order to free up a hand to use to
manipulate instruments through the otoscope, I transfer the otoscope to my left hand,
still maintaining traction on the ear with the left hand as well. I use my right hand to
manipulate instruments. (review ear instruments)
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| A wire ear loop is
being introduced into the ear canal through the otoscope. The loop is used to
"scoop" or "scrape" debris from the ear canal. Always be cautious when
introducing instruments into the ear canal. The ear drum can easily be accidentally
ruptured. |
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| After removing formed debris from the ear
canal using a loop you may want to lavage the ears to dislodge debris. Sterile saline is
the preferred lavage solution if the ear drum is ruptured or if you are not sure of the
integrity of the ear drum. The lavage solutions are introduced using a syringe, bulb
syringe or water pic. If a water pic is used the pressure settings should be low and the
applicator should be introduced so that the water jet is against the wall of the ear canal
rather than directed against the tympanic membrane. Confirm adequate insuflation of the
endotracheal tube as fluid can pass through the Eustachian tubes into the pharynx if the
ear drum is ruptured. There are other types of lavage
solutions that can be used. Check the manufacturers recommendations regarding use in
patients with ruptured ear drums. |
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| The ear canals should be massaged
intermittently during the lavage to break up debris so it can be lavaged out of the ear
canal. |
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| After lavage the ear canals should be dried. A
plastic "tom cat" urinary catheter or a flexible red rubber urinary catheter
attached to a 3 or 6 ml syringe is an effective method by which to gently suction residual
fluid from the ear canals. Cotton tipped applicators can be used to absorb residual fluid.
A mechanical suction unit can also be used to suction fluid from the ear canals. Cotton
balls can be used to clean and dry the visible portions of the inner aspect of the
pinnae. |
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After thorough cleaning, topically applied medications are
more likely to be effective.
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