Dogs with excessive thirst and urination are a common problem. Sometimes, the owner may not notice the problem until the dog begins to urinate in the house. There are at least 25 possible causes of poluria or polydipsia in dogs. Your veterinarian will need to carefully rule out each possibility until they arrive at a definitive diagnosis. This can take some time so be patient and work with your vet to find the answers.
CONFIRMING PU/PU IN YOUR DOG
Your veterinarian will first confirm that your dog has PU/PD. The amount of water that dogs require in a given day will vary depending on their activity, food moisture, environment temperature, humidity, and other factors. A good guideline for water intake is one ounce per pound of bodyweight per day. For example, a 10-pound dog should consume 10 ounces, a 60-pound dog should consume 60 ounces, and so on.
Officially, polydipsia is when a dog drinks more than 100 milliliters per kilogram of its body weight each day. The vets prefer to use kilograms and milliliters (kg) instead of ounces or pounds. However, when you convert these numbers to the more familiar values for dog owners, it comes out to approximately 15 ounces per 10-pound dog and 91 for a 60-pounder, etc.
It is simple to measure water intake if you only have one dog and close the toilet lids. However, it can be difficult to do so with multiple pets.
A second way to verify PU/PD is to take a sample of the first urine your dog makes in the morning before he drinks for the day. Then, bring this specimen to your vet to be tested (known as a urine specific gravity, USG).
USG refers to the concentration of urine. The urine of a dog with PU/PD will be dilute if it is true. For confirmation, your veterinarian may ask you to send three to four samples in a row.
Your vet should verify that the PU/PD you are observing is not a side effect from any medication your dog might be taking. Side effects of drugs like prednisone, phenobarbital, thyroid medication, oral steroids like Prednisone, diuretics such as furosemide (Lasix), and potassium bromide can lead to excessive thirst and urination. It can also be caused by topical steroids, such as eye drops, ear drops and skin creams containing cortisone. You should not let your dog touch cortisone cream you apply to your skin.
FIRST TESTS OF PU/PD IN DOGS
If your dog was asleep all night, and didn’t wake up to drink water several times during the night, her first morning urine should be concentrated and yellow. Very dilute first morning urine samples will appear pale.
Bring a “free catch” sample of urine with you to your dog’s exam and PU/PD checkup. The workup begins with a physical exam, urinalysis and blood work (chemistry screening and complete blood count, or CBC). The combination of these tests can confirm or eliminate several causes of PU/PD. This includes two of the most common causes.
1. Chronic kidney disease
2. Diabetes mellitus
3. Cushing’s syndrome
The blood and urine samples can be used to diagnose chronic kidney disease. However, the cause of the condition may need further testing such as a urine culture or abdominal ultrasound.
It’s easy to rule out diabetes mellitus (DM). If there is no sugar in your urine and your blood sugar is normal, then there is no DM.
Your veterinarian will now have many clues regarding Cushing’s syndrome. Also known as hyperadrenocorticism (or HAC), your vet will be able to give you hints about the possibility. This includes a physical exam that reveals classic skin and hair changes, a potbellied appearance, blood and urine abnormalities, history of excessive hunger, and panting at home. Further testing is required to confirm a diagnosis.
To rule out HAC, a low dose dexamethasone suppression test (LDDS), should be performed. The test involves a one-day stay in hospital with blood drawn at four and eight hours following a cortisone shot. If the baseline cortisol levels at 0 hours are not low, it is likely that the opposite adrenal gland disorder, Addison’s disease (or underactive adrenal glands), is being ruled out.
Other causes of PU/PD can also be diagnosed in dogs with first veterinary diagnostics. These include hypercalcemia (high blood calcium), anal gland tumors and lymphoma (these can often be seen on physical examination), unspayed females with uterine infection (pyometra), and liver disease.
FINAL ROUND OF TESTS FOR DIAGNOSING P/PD IN DOGS
Let’s assume you have done everything and that all is well. Your veterinarian will need to check for thyroid disease and leptospirosis in dogs. This is an infectious disease that can cause PU/PD in dogs. However, it can sometimes only cause PU/PD in otherwise healthy dogs.
You’ve made it this far without a diagnosis. Now, you need to rule out central diabetes insipidus and psychogenic polydipsia.
CDI is a condition in which the dog’s body does not have an antidiuretic hormone. (ADH) This hormone is produced by the brain and released from the pituitary. ADH is required for kidneys to concentrate urine. ADH is essential for the kidneys to concentrate urine. In an attempt to replace the urine lost, the dog drinks copious amounts water. The end result is PU/PD. CDI can be idiopathic, meaning we don’t know why it occurs, but can also occur due to trauma, inflammation or cancer.
DDAVP (Desmopressin) is used to diagnose CDI. It is a synthetic version of ADH. You can administer it orally, under the skin or nasally. However, severe complications may occur so a veterinarian must be present. These include dangerous electrolyte imbalances and dehydration, especially during trials. CDI is indicated if the dog’s urine levels rise or water intake decreases during trials. DDAVP is the treatment.
Psychogenic polydipsia can be diagnosed if the dog doesn’t respond to DDAVP. This is a behavior issue where the dog drinks excessive amounts of water without apparent reasons. This can lead to extreme cases, where all the water that passes through can cause kidneys to lose their ability concentrate urine. (This is known as medullary washingout). It can become a vicious circle and require time and gradual water loss (only under the direct supervision a veterinarian) in order to restore normal urine concentration.
IT’S A PROCESS
If your dog is suffering from excessive thirst or urination, it’s possible to get answers in the first few steps. Then, treatment will be available for the underlying condition. It’s a good idea to remember that you are excluding diseases with each step.
You and your vet can work together to reduce the number of items on the list and reach a specific diagnosis. You can then take a break from filling the water bowl with dog food and let the dog go in and out. It will be a joyful day!
What causes excessive thirst and urination in dogs? Whole Dog Journal.