7 Key Points for Cushing’s Disease Diagnosis in Dogs: From LDDS/HDDS Preparation to Interpretation

Accurate diagnosis of Cushing’s disease in dogs requires both LDDS and HDDS testing. Here’s a clear overview of how to manage these tests effectively, along with recommended products.

What Are Cushing’s Disease Diagnostic Tests (LDDS/HDDS) in Dogs?

The cornerstone tests for diagnosing Cushing’s disease in dogs and determining its type are the Low-Dose Dexamethasone Suppression Test (LDDS) and the High-Dose Dexamethasone Suppression Test (HDDS). Both involve administering dexamethasone and then collecting blood samples at specific intervals (before administration, 4 hours post-administration, and 8 hours post-administration) to measure the adrenal cortex hormone (cortisol) response. - High sensitivity: The LDDS serves as a screening test to detect Cushing’s disease, boasting a high sensitivity of approximately 90–95%. - Diagnostic criteria: These tests provide critical data that help veterinarians make diagnoses and differentiate between types. - Confirmatory testing: A Cushing’s diagnosis is confirmed using either the LDDS or an ACTH stimulation test, with the choice depending on the individual case. - Type differentiation: The HDDS helps distinguish between pituitary-dependent (PDH) and adrenal-dependent Cushing’s in about 75% of cases. If cortisol levels are suppressed, the condition is classified as PDH; if not suppressed, further testing such as ultrasound is required.

Selection Criteria: Tips for Choosing a Clinic for Cushing’s Disease Testing

When choosing a test, it’s important to consider factors such as accuracy, safety, turnaround time, and cost. It’s essential to consult with your veterinarian to determine the most appropriate test for your pet’s condition.

Highly accurate tests: These provide reliable diagnostic results with clear interpretation.

Safe tests: These involve minimal side effects and cause less stress to your dog.

Quick results: Results are typically available within a week.

Cost-effective: The cost aligns with insurance coverage and your personalized budget.

Available at veterinary clinics: These tests are performed at facilities equipped with specialized equipment and trained professionals.

Check 1: Whether Accurate Tests Such as LDDS and ACTH Stimulation Are Performed

Cushing’s disease (hyperadrenocorticism) is difficult to diagnose with a single test, so precise diagnostic procedures such as the low-dose dexamethasone suppression test (LDDS) or ACTH stimulation test must be performed with blood samples collected at exact time intervals. Since each test has specific requirements for timing and procedure, it’s best to choose a clinic that strictly adheres to these protocols. Even slight deviations in timing can skew results, so it’s important to seek care at a facility with experience in endocrine testing. Also, make sure the veterinarian clearly explains which tests are being performed and why.

Check 2: Whether Symptom Assessment and Basic Tests Are Conducted Together

If your pet drinks excessive amounts of water, urinates frequently, develops a distended abdomen, or experiences hair loss, Cushing’s disease should be suspected. However, these symptoms can overlap with other conditions such as diabetes or kidney disease, so it is important to assess the baseline health status through blood and urine tests to rule out other causes. Choose a veterinary clinic that determines the need for advanced diagnostics by comprehensively evaluating both the clinical signs and initial test results. Opt for a clinic that takes a step-by-step approach rather than immediately recommending extensive testing.

Check 3: Whether Results Are Interpreted to Differentiate Type and Guide Treatment

Cushing’s disease is divided into pituitary-dependent (PDH) and adrenal-dependent (ADH) forms, and because the treatments differ, accurate differentiation is crucial. It’s best to choose a clinic where the veterinarian can determine the type using a high-dose dexamethasone suppression test (HDDS) or abdominal ultrasound, and then clearly explain how those results guide treatment options such as trilostane or other approaches. Since medication response must be monitored through follow-up tests to adjust dosages accordingly, select a clinic that provides guidance for long-term management.

This is not a table recommending specific products or clinics, but criteria to reference when consulting a veterinarian. Treatment and testing decisions must always be made together with a veterinarian through an examination.

Post-Test Care Tips

After the test, it’s important to closely monitor your dog’s condition. Temporary fatigue or loss of appetite may occur.

Provide rest: Allow your dog to rest in a quiet environment for 1–2 hours after the test.

Manage meals: Withhold food for 4 hours after the test, then offer small amounts gradually.

Limit activity: Reduce physical activity for one day following the test.

Watch for side effects: Contact your vet immediately if you notice vomiting, diarrhea, or signs of shock.

Review results: Wait for your veterinarian to explain the results, and don’t hesitate to ask any questions you may have.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

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