Canine Cushing's Case Files: The ins and outs of detection and treatment-Case file: Dogs with recurring pyoderma (Sponsored by Dechra Veterinary Products)

While hyperadrenocorticism would probably be the number one differential diagnosis in dogs with classic clinical signs—pot belly, bilateral symmetric alopecia, polyuria, and polydipsia—this diagnosis may be overlooked in patients with more subtle clinical signs. Cushing's syndrome can be challenging to identify because of its variable clinical manifestations in our canine patients. One of the trickier clinical presentations for veterinarians to keep in mind is recurring pyoderma.

In our practice, we find that some patients with hyperadrenocorticism experience recurring skin infections, but show none of the classic physical findings usually associated with cushing's syndrome. Instead, the only visible manifestation of cushing's disease is their recurring skin infections (Figure 1).

Figure 1. A dog with pituitary-dependent hyperadrenocorticism and secondary mucocutaneous pyoderma.

Remember pyoderma causes

Superficial staphylococcal skin infections or superficial pyodermas are common in dogs and have many different underlying causes. However, these underlying causes can be separated into two major categories: allergy and endocrinopathy. The patient's age can be a diagnostic clue since many allergic dogs will initially be presented at a younger age, whereas dogs with an endocrinopathy, such as hyperadrenocorticism or hypothyroidism, will be middle-aged or older when their infections develop.

For patients that were confirmed to have and were treated for superficial pyoderma that resolved but then recurred, veterinarians should try to accomplish two goals: 1) address any active infection more intensively with topical products, and 2) identify and treat the underlying cause of the infection.

Address pyoderma topically

Because there has been a dramatic worldwide increase in the incidence of methicillin-resistant Staphylococcus pseudintermedius (MRSP) skin infections in dogs during the past five years (Figure 2),1-3 it may no longer be appropriate or acceptable to simply repeatedly treat such patients with systemic antibiotics. In my experience, topical chlorhexidine works well in patients with superficial bacterial skin infections. I have found that one of the more effective topical antimicrobial formulations to add to my pyoderma therapy regimen is 4% chlorhexidine combined with TrisEDTA (TrizCHLOR™ 4 – Dechra Veterinary Products). TrizCHLOR 4 is available in shampoo, spray-on, and medicated wipe formulations, and is indicated for support of healthy skin in animals with conditions responsive to chlorhexidine. In my practice, addressing an active superficial pyoderma topically with TrizCHLOR™ 4 may help resolve the infection without the use of systemic antibiotics, if the patient can be bathed several times a week and the infected area is sprayed twice daily. I also use these topicals to help reduce the recurrence of infection until the underlying cause can be identified and controlled.

Figure 2. Dorsal trunk of a bulldog with a large plaque of calcinosis cutis and draining furuncles caused by methicillin-resistant Staphylococcus pseudintermedius superficial and deep skin infection due to pituitary-dependent hyperadrenocorticism.

Identify the underlying cause of recurring pyoderma

The most common reason dogs develop recurring pyoderma is allergic disease, such as atopic dermatitis, parasite hypersensitivity, and adverse reactions to food. Most allergic patients exhibit pruritus or skin erythema even after the infection has resolved. Examine patients carefully after the infection is cleared for erythema of the interdigital, axillary, inguinal, or pinnal regions, which could suggest a primary allergic disease. If erythema or pruritus is not observed, then screening the patient for underlying endocrine diseases (hyperadrenocorticism or hypothyroidism) is indicated.

Screen for hyperadrenocorticism

A complete blood count, serum chemistry profile, and urinalysis provide important baseline data. Abnormalities in patients with hyperadrenocorticism may include neutrophilia, lymphopenia, eosinopenia, monocytosis, elevated serum alkaline phosphatase activity, hyperglycemia, and dilute urine (specific gravity < 1.020). Patients with early hyperadrenocorticism may exhibit few or none of these abnormalities.

After obtaining blood test results, the urine cortisol:creatinine ratio (UCCR) is an inexpensive and relatively easy screening test for hyperadrenocorticism. Ask the owner to collect a sample of the dog's first urine of the morning at home, in a nonstressful environment, and at least two or three days after the last clinic visit to avoid a false-positive UCCR result. This test can frequently give false-positive results, so an elevated UCCR must not be used alone to diagnose hyperadrenocorticism. An abnormal result does indicate that more testing is warranted. Conversely, a normal UCCR result rules out hyperadrenocorticism, and another cause of the dog's clinical signs should be pursued.

Confirm hyperadrenocorticism

If the UCCR results are abnormal and allergic skin disease has been ruled out, either a low-dose dexamethasone suppression (LDDS) test or an adrenocorticotropic hormone (ACTH) stimulation test should be done to help confirm a diagnosis of hyperadrenocorticism. (See the previous Canine Cushing's Case Files in this series, Dali and Princess.) In our dermatology patients, we find the LDDS test has higher sensitivity (fewer false-negative results) than the ACTH stimulation test; thus, it is our preferred next test. However, if a patient has serious concurrent metabolic abnormalities, such as diabetes mellitus or kidney failure, or has received long-term glucocorticoid therapy, the LDDS test may give false-positive results, in which case an ACTH stimulation test would be preferable. Abdominal ultrasonography can also be a useful diagnostic tool in dogs with hyperadrenocorticism.

Treat hyperadrenocorticism

If a dog is confirmed to have pituitary- or adrenal-dependent hyperadrenocorticism, we initiate treatment with VETORYL® (trilostane) Capsules at the low end of the labeled dose range (2.2 mg/kg/day, given with food). After 10 to 14 days of therapy, we perform an ACTH stimulation test four to six hours after the VETORYL capsules are administered. We also perform a thorough physical examination and a serum chemistry profile with electrolyte measurements, and we consult with the owner to assess any clinical changes. The ACTH stimulation test results and electrolyte concentrations are assessed for signs of hypocortisolemia (cortisol concentration < 1.45 µg/dl). If none are seen, we continue the original VETORYL Capsules dose prescribed.

Thirty days after beginning VETORYL Capsules therapy, we perform another ACTH stimulation test and evaluate the results for hypocortisolemia and hypercortisolemia (cortisol concentration > 9.1 µg/dl). If needed, we increase or decrease the VETORYL capsules dosage. If the dose is changed, we repeat an ACTH stimulation test in 10 to 14 days. If the dose is not changed, we repeat the ACTH stimulation test 90 days after the first day of VETORYL Capsules therapy and then every three months thereafter.

When dogs receive long-term VETORYL Capsules therapy, veterinarians should pay close attention to abnormalities in electrolyte concentrations or other blood test results and any reports from owners regarding a dog's poor appetite, lethargy, vomiting, diarrhea, weakness, or anorexia.

Figure 3. The same patient as in Figure 2 after 11 months of treatment with VETORYL® (trilostane) capsules and TrizCHLOR™ 4 shampoo. One month of systemic antibiotic treatment was required initially. The dog has some permanent hair loss from follicle destruction caused by the initial MRSP skin infection.

Dr. Lewis' perspective

Recurring pyoderma is one of the more common dermatologic conditions veterinarians encounter. In this age of ever-increasing antibiotic resistance, it is imperative for veterinarians to identify and treat the underlying cause of recurring skin infections (Figure 3) and to consider topical antimicrobial products to help resolve active superficial skin infections so that the use of systemic antibiotics can be minimized. Because hyperadrenocorticism is one of the known causes of recurring pyoderma, veterinarians should be familiar with this disease and its treatment.

REFERENCES

1. Coyner KS. The emergence and prevalence of MRSA, MRSP, and MRSS in pets and people. Vet Med 2012;107(12):516-521.

2. Frank La, Loeffler A. Methicillin-resistant Staphylococcus pseudintermedius: clinical challenge and treatment options. Vet Dermatol 2012;23:283-291.

3. Bannoehr J, Guardabassi L. Staphylococcus pseudintermedius in the dog: taxonomy, diagnostics, ecology, epidemiology and pathogenicity. Vet Dermatol 2012;23:253-266.

The cases described in this article were solicited from the prescribing veterinarian and may represent atypical case studies. Similar results may not be obtained in every case.

Thomas Lewis, DVM, DACVD, Dr. Lewis’ principal interests include investigating the role of allergies and their effect on the skin. Dr. Lewis is the founder of dermatology for Animals, with clinics in multiple states.

Dr. Thomas Lewis

Hyperadrenocorticism affects many adult dogs. Whether the disease is pituitary-dependent (80% to 85% of spontaneous cases) or adrenal-dependent (15% to 20% of cases), the clinical and laboratory abnormalities associated with it result from chronic hypercortisolemia. Clinical signs of hyperadrenocorticism at the time of diagnosis can vary widely, and they develop so gradually that owners often mistake the signs for "normal" aging. Being aware of the more subtle signs of canine hyperadrenocorticism can be key to early diagnosis and initiation of therapy.

COMMON CLINICAL SIGNS OF CANINE HYPERADRENOCORTICISM

Whenever possible, pituitary-dependent hyperadrenocorticism and adrenal tumors should be differentiated to help guide therapy and patient monitoring. Early diagnosis and management of canine hyperadrenocorticism may not only improve the patient's clinical signs but may also keep the more severe consequences of Cushing's syndrome from developing.

Learn more with these online resources

Go to the Dechra Veterinary Products CE Learning Center at www.dechrace.com and choose one of the online CE modules to learn the latest on managing feline hyperthyroidism and canine hyperadrenocorticism. Plus earn free CE!

• Diagnosing and treating canine hyperadrenocorticism

Presented by Audrey K. Cook, BVM&S, MRCVS, DACVIM, DECVIM, and David s. Bruyette, DVM, DACVIM

• Cushing's disease: Inside and out

Rhonda Schulman DVM, DACVIM, and John Angus, DVM, DACVD

• Diagnosing and treating feline hyperthyroidism

Presented by Andrew J. Rosenfeld, DVM, DABVP

Then get your whole team on the same page, by visiting the Team Meeting in A Box section at www.dechrace.com

• Stop getting burned by ear infections

How you handle otitis externa and ear infections can make or break client bonds—and dogs' well-being. Use this Team meeting in a Box to create a team approach to help pet owners and heal patients.

• Coping with Cushing's syndrome

Pets with Cushing's syndrome suffer from a chronic illness that will be managed throughout the pet's life, not cured. This Team Meeting in A Box will help you deliver a successful team-wide approach.

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