Swollen Testicles--Getting the Right Diagnosis

Look outside the normal. Consider abnormal or atypical illness patterns

We’ve been discussing how difficult it is to get the right diagnosis for a pet’s illness and have identified 5 problem areas:
1. Working with incomplete or misleading information
2. Being presented with a pattern of illness that isn’t normal or typical
3. Grabbing onto a major symptom and thinking that’s where the focus should be
4. Considering the problem only in light of what local pets develop
5. Using stereotypes such as breed or age

We discussed the first problem in detail, and now let’s cover the second problem: being presented with a pattern of illness that isn’t normal or typical.

Let’s look at an achingly painful problem, swollen testicles.

Cancer is a common cause of swollen testicles
When an older male dog that has never been used for breeding develops swollen testicles, veterinarians usually suspect cancer and we put Sertoli cell tumors, seminomas, interstitial cell (Leydig) tumors, and mast cell tumors high on our list of potential problems.

Cancer affects half of all dogs
We think cancer is the most likely diagnosis because neoplasia affects half the canine population. That’s right. Our senior dogs have a 1 in 2 chance of developing cancer. In addition, 75% of tumors affecting the male urogenital tract occur in the testicles.

Veterinarians also think of cancer as a potential diagnosis because we tell every family with a male puppy: “We should neuter your dog because if your dog doesn’t have testicles, it won’t get cancer of the testicles.” Then, whenever we see an adult dog with testicles, we think: cancer.

Brucella can also cause swollen testicles
With swollen testicles in an unneutered male, we also want to know whether the dog has been used for breeding or whether it has lived in a breeding kennel. Breeding allows transmission of brucella, a bacteria that causes brucellosis. In males, brucellosis causes achingly painful testicular swelling. Historians think Napoleon had brucellosis and that’s why he looked so uncomfortable sitting on a horse.

Disregarding brucella as a diagnosis because it doesn't fit the pattern
If the family tells us that the dog was never used for breeding and has never been resident in a breeding kennel, we take brucella infection right off our list of potential diseases causing this dogs swollen testicles. What a mistake that can be: we’d be missing the atypical or abnormal case of brucellosis caused by food. Although food-borne brucellosis is uncommon in the United States, it is common in the Mediterranean and can occur when pets are fed unpasteurized sheep or goat cheese imported from this area. Who would have thought….

Swollen penis (balanitis) caused by Lyme disease
Another infection that has an atypical presentation as swollen penis (balanitis) is Lyme disease. Lyme disease usually causes joint problems, but it also causes balanitis in humans and should be considered in the differential list of diseases for dogs presenting with a swollen penis.
If we want to make the correct diagnosis for pets, we can’t get stuck on finding a diagnosis that fits the normal or typical pattern of illness. We should consider the atypical and abnormal, too.

What's coming: Focusing on one major symptom
In the past few Caring for Pets blog entries, we’ve discussed two major problems leading to misdiagnosis (Working with incomplete or misleading information and Being presented with a pattern of illness that isn’t normal or typical). In the next blog, we’ll cover another major problem leading to misdiagnosis: Grabbing onto one major symptom and thinking that’s where the focus should be.