Optimal treatment of any persistent medical condition depends on establishing the correct diagnosis. The symptom group polyuria and polydipsia has many different potential causes, and it is important to identify the underlying cause before beginning treatment.
Diagnose and treat the cause The pet owner may report increased thirst and urination. If the physical examination and baseline laboratory test results are normal, the owner can measure water intake at home for a few days to document the presence of polydipsia before pursuing further diagnostic tests. Polyuria and polydipsia usually do not constitute an emergency (hypercalcemia is an exception), but occasionally these symptoms arise from serious diseases that require prompt attention (e.g. diabetes mellitus, hypoadrenocorticism).
Hyperadrenocorticism
Specific diagnostic tests include adrenocorticotropin response test, low- and high-dose dexamethasone suppression tests, urine cortisol-to-creatinine ratio, abdominal ultrasound, and occasionally other specialized tests such as measurement of blood concentration of adrenocroticotropin and elaborate imaging studies such as computerized tomography and magnetic resonance imaging.
Renal glucosuria
Diagnosis is based on finding glucose in the urine in a pet that has a normal blood glucose concentration. This disorder is most likely in certain breeds of dogs such as Basenji dogs and Norwegian elkhounds.
Kidney insufficiency or failure
Diagnosis is based on serum biochemistry tests and urinalysis. Treatment is based on rehydrating the pet, trying to slow the progression of the kidney disease by dietary modification, and treating complications such as hypertension and urinary tract infection.
Post-obstructive diuresis (polyuria that develops after relief of urinary obstruction)
This form of polyuria is transient but the pet must receive adequate fluid therapy to prevent dehydration during recovery.
Diabetes mellitus
This diagnosis is based on high blood glucose concentration and the presence of glucose, and often incompletely broken down fat products called ketones in the urine. Treatment depends on severity and may include hospitalization with intensive fluid and electrolyte therapy in conjunction with administration of short-acting insulin or outpatient management with long-acting insulin.
Hypokalemia
Treatment is based on correcting the underlying cause of potassium depletion. Causes may include: chronic loss of appetite, chronic muscle wasting, vomiting; diarrhea; administration of potassium-deficient fluids; potassium loss through the kidneys; alkalosis (high blood pH); administration of drugs that promote potassium loss; or some combination of these factors. Oral administration of potassium gluconate is the safest method of potassium supplementation.
Hypercalcemia
High blood calcium concentration can be a medical emergency. Hypercalcemia often is a clue to underlying malignancy. Treatment with intravenous fluids, diuretics, and specific drugs may be recommended.
