From history to cytology: A systematic approach to canine ear infections

Addressing recurrent otitis externa in dogs requires a focus beyond symptomatic treatment. During this interview with dvm360, Darin Dell, DVM, DACVD, emphasized the critical importance of identifying and managing the underlying root causes, such as allergies or ear mites, to achieve long-term resolution and more through the primary, secondary, predisposing, and perpetuating causes (PSPP) approach.

Below is a transcript, edited lightly for clarity.

dvm360: Starting with your name, can you tell us a little bit about yourself?

Darin Dell, DVM, DACVD: My name is Dr Darin Dell. I'm a veterinarian here in Wheat Ridge, Colorado, just west of Denver. I started working at a veterinary clinic in my little hometown when I was 14 [years old], so I was indoctrinated early. [I] started out cleaning kennels, mopping the floors, holding animals, [and] then answering the phones and helping the doctor on farm calls. So veterinary medicine is really how I grew up. That's why I went to vet school.

[I] went to the University of Illinois, graduated in 2001, worked for several years in general practice, and then did some overnight [emergency department work] before I decided to become a dermatology resident. Life is a whole lot easier as a dermatology resident [and then] as a dermatologist. It's also just clearly the specialty that I love; skin makes sense to me. I love making a difference for [those] with these long-term problems, and it makes me happy.

dvm360: How would you use the PSPP concept to explain why recurrence happens and your diagnostic plan to a client who is frustrated that their dog's ear infection keeps returning?

Dell: Otis externa is super frustrating for clients. It's super annoying for the pet, too. So PSPP, when you're talking to the client, helps you say, "All right, we're here because there's an infection today and your dog's ear is very, very inflamed, so we need to treat that." But underneath that is the primary problem. And the primary problem, whether that's allergies, ear mites, or there was a tick in the ear or something else, that's what truly needs to be handled so that you stop doing this every month or every 6 weeks. We have to get to the root cause.

dvm360: What are the top 3 diagnostic steps you would take to find the underlying cause of recurrent otitis externa, and in what order?

Dell: Three is good; 4 is better. No. 1—and if we had 4 options—would be history. You have to find out not just when the episode started but [also] when the first ear infection ever [occurred]. People like to focus on the "right now" because they're living the stress…. But when was the first time you ever saw an ear problem? History is important.

The entire physical exam…we're looking for: Are there allergy changes on the skin? Are the paws red? Is the groin hyperpigmented? Those sorts of things. Then the otoscopic exam. I think this also doesn't get taught very well. There are minor changes that you can observe in the ear canal that can help guide you on how you're going to treat and what you're going to tell the client. But you've got to look at every ear so you know what normal is…[and] decide variations of abnormal.

Then No. 4, for me, would be the cytology of the ear smear…. Do I have white blood cells? Do I have yeast? Do I have bacteria? The kind of bacteria can give you a lot of clues about what you're going to treat with and how severe this is. It also helps you monitor progress. So that's the other thing that I see that doesn't happen a lot: monitoring progress as you go.

We really want to see that, yes, I've cleared the entire infection, not just part of the infection. If you don't know what your infection was when you started, you don't know where you are halfway through.