College of Veterinary Medicine

Small Animal DX & Therapeutic Techniques

Otoscopic Examination of the Dog & Cat


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.

ear_lat_recum.JPG (23347 bytes) 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

top of page

ear_diagram.JPG (23830 bytes) 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.

 

top of page

ear_external.JPG (23001 bytes) ear_inner.JPG (28761 bytes)
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.

top of page

ear_smell.JPG (21406 bytes) 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.

top of page

ear_pull.jpg (19924 bytes)

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.

ear_pull_pinne_cls.jpg (30371 bytes)

top of page

ear_insert_scope.JPG (24212 bytes)

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.

 

ear_insert_tip_cl.JPG (29091 bytes)
eardrum.jpg (13394 bytes) 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.

 

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.

top of page


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)
ear_look_little_lens.JPG (18920 bytes) ear_look_little_cl.JPG (19416 bytes)

top of page

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.
ear_scope_instruments.JPG (24056 bytes) ear_instrumentation.JPG (26377 bytes)

top of page

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. 

ear_bulb.jpg (23937 bytes) ear_bulb_cl.JPG (26677 bytes)

top of page

The ear canals should be massaged intermittently during the lavage to break up debris so it can be lavaged out of the ear canal.
ear_massage.JPG (22171 bytes) ear_masssage_cls.JPG (27391 bytes)

top of page

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.
ear_asp2.jpg (28091 bytes) ear_asp2_cl.JPG (29882 bytes)

After thorough cleaning, topically applied medications are more likely to be effective.

top of page

otoscopic exam main | otoscopic equipment | Diagnostic Techniques Laboratory  

Last Edited: Feb 02, 2009 4:06 PM   

College of Veterinary Medicine, PO Box 647010 , Washington State University, Pullman WA 99164-7010, 509-335-9515, Contact Us  Safety Links