Polydipsia and Polyuria (excessive drinking and urinating) in Dogs

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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. 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

    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

    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.

    Home Care

    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.

    Preventative Care

    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.

    Polyuria and polydipsia are not specific for any one disease, but can be caused by several disorders including:

  • 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)

  • Urinalysis

  • 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.

    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.

  • "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 result of a deficiency of anti-diuretic hormone secretion from the pituitary gland at the base of the brain. It can be "idiopathic" (that is, of unknown cause), due to head trauma or due to a tumor in the pituitary gland. Water deprivation testing and response to anti-diuretic hormone administration confirm the diagnosis. A drug called DDAVP (a synthetic form of anti-diuretic hormone) is administered intra-nasally in drop form to treat central diabetes insipidus.

  • Hypoadrenocorticism

    This disorder is diagnosed by the adrenocorticotropin response tests (failure to respond). Treatment consists of intravenous fluids and replacement of missing steroid hormones.

  • Pyelonephritis

    This disorder can be difficult to diagnose because identification of urinary tract infection by urine culture and sensitivity does not localize the infection to the kidneys. Diagnosis requires integration of complete blood count results, urine culture and sensitivity results, contrast dye study of the kidney ("intravenous pyelogram" or "excretory urogram"), ultrasound of the kidney, and possibly kidney biopsy. Treatment requires long-term administration of antibiotics.

  • 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")

    This cause of polyuria and polydipsia is managed by discontinuing the offending medical 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

    Diagnosed by serum biochemistry tests (including bile acids), abdominal ultrasound, and liver biopsy if necessary.

    Definitive therapy of polyuria and polyuria depends on the underlying cause.

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