Polydipsia and Polyuria (excessive drinking and urinating) in Dogs
Overview of Excessive Drinking and Urinating in Dogs
Polydipsia and Polyuria are common problems in dogs. The term polydipsia refers to excessive thirst manifested by excessive water intake, which in turn usually leads to polyuria, which is the formation and excretion of a large volume of urine. Polyuria and polydipsia are commonly abbreviated and referred to as PU/PD.
Polydipsia and polyuria are early signs of several diseases, including:
- Kidney failure
- Diabetes mellitus
- Uterine infection (called pyometra)
- Liver disease
- High blood calcium
- Uncommon abnormalities of the pituitary gland
- Inability of the tubules of the kidney to reabsorb water properly (i.e. “nephrogenic” diabetes insipidus)
Dogs normally take in about 20 to 40 milliliters per pound of body weight per day, or about 3 to 4 cups of water per day for a 20 pound dog. Anything more than that, under normal environmental conditions, is considered polydipsia.
You should watch your dog for increased thirst and urinations. Some dogs may begin drinking from a dripping faucet in the sink or from an open toilet bowl. However, if you want to determine how much your dog is drinking, allow him only one source of water and subtract the amount left in the bowl after 24 hours from the amount you put in originally. If you determine that your pet is drinking excessively, make an appointment with your veterinarian.
Diagnosis of Polyuria and Polydipsia (PU/PD)
One of the first steps in the evaluation of a dog with polyuria and polydipsia is to determine the urine concentration by a test called “urine specific gravity.” The specific gravity of pure water is 1.000. Polyuria is suspected if the urine specific gravity is less than 1.035. This can be verified by measuring daily urine output. Polyuria is present if the dog’s daily urine output is greater than 20 milliliters per pound of body weight per day.
Several diagnostic tests may be needed to determine the cause of polyuria and polydipsia because many different diseases may cause these symptoms. Tests may include:
- Complete medical history and physical examination including palpating the abdomen to check kidney and liver size, checking for vaginal discharge in females, and palpating the thyroid gland.
- The history that includes the determination of drug administration (e.g. diuretics, anticonvulsants, cortisone-type drugs, salt; or recent fluid therapy); reproductive status (i.e. sexually intact or spayed) in females; occurrence of urinary accidents in the house; abnormal odor or appearance of the urine; and the presence of weight loss, appetite change, or any other abnormalities.
Treatment of Polyuria and Polydipsia (PU/PD)
There are several potential causes of polyuria and polydipsia, and the underlying cause of these symptoms must be determined before appropriate treatment can be initiated.
The occurrence of polyuria and polydipsia usually does not constitute an emergency, but several potentially serious diseases (such as diabetes mellitus, kidney failure, liver failure or high blood calcium caused by a malignancy) may be the underlying cause of the symptoms. Hypercalcemia can be a medical emergency and if identified should be treated appropriately with intravenous saline solution and diuretics.
You should also monitor your dog for any clinical abnormalities and discuss them with your veterinarian. Monitor the amount of water consumed by your dog and try to identify any changes in urinary behavior and urine output. Also monitor your dog’s appetite and activity level. Discuss any changes you observe or concerns you may have with your veterinarian.
Polyuria and polydipsia cannot be prevented, and successful treatment depends on identification of the underlying disease causing these symptoms.
Monitor your pet for any outward signs of illness and discuss them with your veterinarian. Monitor the amount of water your pet drinks and observe your pet for changes in his urinary habits. Discuss any changes with your veterinarian.
There are no general recommendations for prevention of polyuria and polydipsia. Treatment depends upon the underlying cause.
In-depth Information on Polyuria and Polydipsia in Dogs
Polyuria and polydipsia are not specific for any one disease, but can be caused by several disorders including:
Causes of Polyuria and Polydipsia in Dogs
- Endocrine (hormonal) disorders
- Hyperadrenocorticism (overactivity of the adrenal glands)
- Diabetes mellitus
- Hypoadrenocorticism (underactivity of the adrenal glands)
- Kidney disorders
- Renal glucosuria (a defect of the kidney tubules leading to spillage of glucose in the urine)
- Kidney failure (more commonly acute, sometimes chronic)
- Pyelonephritis (infection of the kidneys)
- Increased production of urine after relief of urinary tract obstruction (“post-obstructive diuresis”)
- Loss of normal salts and chemicals (urea) in the kidney that facilitate water reabsorption (“renal medullary washout”)
- Impaired response of the kidney tubules to anti-diuretic hormone that normally promotes water reabsorption (“nephrogenic” diabetes insipidus)
- Electrolyte abnormalities
- High blood calcium concentration (hypercalcemia)
- Low blood potassium concentration (hypokalemia)
- Miscellaneous disorders
- Abnormally high red blood cell numbers leading to thickened blood (“polycythemia”)
- Infection of the uterus (“pyometra”)
- Liver disease
- Defective release of anti-diuretic hormone from the pituitary gland (“central” or “pituitary” diabetes inspidus)
- Psychogenic polydipsia (a behavioral problem that leads to compulsive water drinking)
- Administration of fluids, salt, diuretics or cortisone-like drugs
The most common causes of polyuria and polydipsia in dogs are chronic kidney failure, hyperadrenocorticism and diabetes mellitus.
Diagnostic tests used to determine the cause of polyuria and polydipsia should be considered based on results of a complete medical history and thorough physical examination. Baseline diagnostic tests that your veterinarian may request to evaluate a pet with polydipsia may include:
- Measurement of water intake at home by the owner (to document the presence of polyuria).
- Complete Blood Count (CBC)
- Serum chemistry tests (including electrolytes)
- Urine culture and sensitivity
Depending on the clinical situation, your veterinarian might recommend additional diagnostic tests to further investigate the cause of polyuria and polydipsia and provide optimal medical care for your pet. Examples of other tests that may be requested include:
- Plain abdominal X-ray
- 24-hour creatinine clearance to evaluate the filtering function of the kidneys
- Water deprivation testing and anti-diuretic hormone response test
- Adrenocorticotropin response test, dexamethasone suppression test (low dose and high doses), and urine cortisol-to-creatinine ratio to evaluate for hyperadrenocorticism in dogs
- Serum parathyroid hormone measurement
- Abdominal ultrasound exam
- Chest X-rays, cytological evaluation of lymph node and bone marrow aspirates to evaluate for the cancer lymphosarcoma in pets with hypercalcemia (high blood calcium concentration)
- Special dye contrast study of the kidneys (called intravenous pyelography or excretory urography) to evaluate for pyelonephritis.
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.
Treat the Cause of Polyuria and Polydipsia
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).
- 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
- 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
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.
- “Nephrogenic” diabetes insipidus
This disorder is a result of the kidney’s inability to respond properly to anti-diuretic hormone, which normally facilitates water reabsorption in the kidney tubules. Usually this disorder is secondary to other problems (e.g. hypokalemia, hypercalcemia), but very rarely it can represent a congenital kidney defect (a problem present at birth). Treatment depends on the initiating cause or symptomatic treatment may be necessary when no underlying disorder can be identified.
- Central diabetes insipidus
This disorder is diagnosed by the adrenocorticotropin response tests (failure to respond). Treatment consists of intravenous fluids and replacement of missing steroid hormones.
- Psychogenic polydipsia (compulsive water drinking)
This behavioral disorder is diagnosed on the basis of water deprivation testing after excluding other causes of polyuria and polydipsia. Most veterinarians perform gradual water deprivation to avoid confusion that can arise from loss of normal kidney concentrating ability that can arise simply as a result of longstanding polyuria (“renal medullary washout”). Treatment includes behavioral modification, gradual water restriction and occasionally drugs to counteract obsessive-compulsive behavior.
- Iatrogenic (“caused by treatment”)
- Pyometra (uterine infection)
This disorder is diagnosed based on history (i.e. older intact female dog), complete blood count, and abdominal X-rays or ultrasound. Treatment involves surgery to remove the infected uterus or occasionally prostaglandin type drugs to evacuate the uterus if it is open and draining.
- Liver disease