Solution for Case 27
Diagnosis: Tentative diagnosis is Diabetes Mellitus based on the hallmark clinical signs of polyuria, polydipsia, polyphagia, and weight loss, in conjunction with significant hyperglycemia and glucosuria.
DDx: The primary differential diagnoses for significant PU/PD in a dog include Hyperadrenocorticism (Cushing's Disease) and Chronic Kidney Disease (CKD). However, the profound hyperglycemia and glucosuria make Diabetes Mellitus the leading diagnosis.
Diagnostic tests:
The combination of persistent fasting hyperglycemia (blood glucose > 250 mg/dL) and glucosuria is diagnostic for Diabetes Mellitus in dogs. Stress hyperglycemia in dogs rarely exceeds 200 mg/dL, so the value of 485 mg/dL is definitive.
A fructosamine level could be measured to confirm sustained hyperglycemia over the previous 2-3 weeks, but it is not strictly necessary for diagnosis in this case given the classic signs and degree of hyperglycemia.
The presence of trace to small ketones in the urine indicates the body is breaking down fat for energy and warns of the potential to progress to Diabetic Ketoacidosis (DKA), a medical emergency. Since this patient is still eating and appears bright, she is classified as having uncomplicated diabetes.
Definitive diagnosis: Diabetes Mellitus with secondary diabetic cataracts.
Treatment: The goals of treatment are to eliminate the clinical signs, prevent complications like DKA and hypoglycemia, and provide a good quality of life.
Insulin Therapy: This patient was started on an intermediate-acting insulin. A common starting choice is a porcine lente insulin (Vetsulin®) or NPH insulin (Humulin-N®, Novolin-N®) at a dose of 0.25 - 0.5 Units/kg every 12 hours. The injections are given subcutaneously immediately following a meal.
Dietary Management: The dog will be transitioned to a prescription therapeutic diet formulated for diabetic dogs, which is typically high in fiber and complex carbohydrates. The owner was instructed to feed two equal-sized meals every 12 hours, just prior to each insulin injection. No other treats or food should be given to ensure consistent glucose absorption.
Client Education & Monitoring: This is a critical component of management. The owner was taught how to handle and administer insulin and educated on the signs of hypoglycemia (weakness, lethargy, stumbling, seizures). The plan is to have the dog return in 7-10 days to perform a blood glucose curve, where blood glucose is measured every 2 hours for 12 hours to assess the insulin's effectiveness and duration. The dose will be adjusted based on the curve results and the resolution of clinical signs.
Cataracts: The owner was informed that the cataracts are a direct and common result of diabetes in dogs and are unlikely to resolve. Once the dog's diabetes is well-regulated, she can be referred to a veterinary ophthalmologist to discuss surgical cataract removal to restore vision.
