double trouble: bilateral conditions in pets

Dr. Kim Smyth
Posted by Dr. Kim Smyth on Jul 23 2013

White puppy dog | Bilateral conditions in pets | Petplan

Pet illnesses and ails run the gamut, from scrapes and sprains to runny eyes and infections. Head to toe, our pets are subject to just about anything – which is part of the reason pet insurance is so popular! When it comes to those illnesses, we hope for them to be small and contained, but sometimes conditions are what we call “bilateral,” or occurring on both sides (right and left) of our pets.

Unilateral conditions, on the other hand, are those that occur on one side. For instance, if your dog has developed conjunctivitis (or what we call “pink eye” in human medicine), it usually is just in one eye, or unilateral, though it can occasionally occur in both eyes (bilaterally). Bilateral conditions are more than just bad luck – sometimes they can tell us that an underlying condition is at hand.

Now, some conditions just naturally occur bilaterally. Hereditary orthopedic conditions, like hip dysplasia and elbow dysplasia often occur on both sides, as do patellar luxations and cranial cruciate ligament ruptures. They don’t always occur at the same time, but in many cases, if you’ve had to repair one knee, the other is likely to be susceptible, too.

Other commonly occurring bilateral primary conditions include:


Stenotic nares

Keratoconjunctivitis sicca


Progressive Retinal Atrophy

Sometimes when we see bilaterally occurring problems, we are reminded that perhaps there is another medical condition causing them. When illnesses are bilateral due to an underlying cause, we call them secondary diseases. It all comes down to local verses systemic illness. Here’s a good example: a bug bite is small and contained, and generally has only local signs (redness, swelling, itchiness). But, if that one local bug bite causes a systemic reaction in an allergic animal, you’ll see signs everywhere – hives, facial swelling, severe whole body itchiness.

The same thing applies with systemic disease and some bilateral conditions; one underlying illness causes another. Below are some common bilateral conditions that are secondary in nature, along with the primary cause:

Bilaterally symmetric hair loss (alopecia). Often, hair loss that is bilateral means there is a hormone imbalance. Hypothyroidism and hyperadrenocorticism (Cushing’s Disease) are common culprits here.

Bilateral retinal detachment can result from high blood pressure.

Bilateral otitis externa (ear infections) can be caused by atopy or food allergies.

Uveitis (inflammation of the inside of the eye) has many causes. When it is bilateral, systemic conditions, such as fungal infection, tick-borne disease, and neoplasia must be considered.

If your pet is affected bilaterally by an illness, don’t fret. Though two sides are concerned, only one treatment is needed!