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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