Diabetes Insipidus in Dogs

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Diabetes insipidus (DI) is a metabolic disorder characterized by excessive, extreme urination, and accompanied by undue thirst. It is either caused by impaired production of a hormone called ADH (anti-diuretic hormone) from the brain (central DI), or an impaired ability of the kidney to respond properly to the ADH (nephrogenic DI).

Central DI can occur if there is damage to the part of the brain that makes the ADH. Trauma or cancer would be potential causes of this kind of damage. Most cases are "idiopathic"; in other words, there is no known cause.

Nephrogenic (originating from the kidneys) DI is a very rare congenital disorder that also occurs for no known reason.

There is no apparent age, gender, or breed predilection for DI. Most cases occur in dogs; cats are rarely affected. As long as dogs with DI have unlimited access to water and are in an environment where excessive urination is not a problem, most dogs do fine and have an excellent life expectancy.

What to Watch For

  • Severe, excessive urination
  • Insatiable desire to drink water
  • Stupor, disorientation, lack of coordination, or seizures if a brain tumor is the primary cause

    Diagnosis

    Diagnostic tests are needed to rule out other common causes of excessive thirst and urination, including:

  • Complete medical history and physical examination
  • Complete blood count
  • Serum biochemistry panel
  • Urinalysis
  • X-rays or ultrasound
  • Bile acid test
  • Urine culture
  • Tests of the adrenal gland
  • Thyroid hormone test
  • Modified water deprivation test is the most important test for confirming a diagnosis of diabetes insipidus

    Treatment

    If therapy is necessary, treatment for diabetes insipidus may include the following:

  • Desmopressin acetate
  • Chlorpropamide
  • Thiazide diuretics
  • Salt restriction

    Home Care and Prevention

    Give medications as directed and make absolutely certain the dog has constant access to water.

    As most cases of central DI are of unknown cause, that is idiopathic, there is no specific preventative care. Dogs with congenital nephrogenic DI should not be bred in case there is a genetic predisposition to the disorder.

  • Diabetes insipidus (DI) is a metabolic disorder in which dogs demonstrate a severe overproduction of urine. The most common form of DI is called central DI, and is due to insufficient production of anti-diuretic hormone (ADH), a hormone responsible for concentrating the urine into a small volume. Dogs with DI urinate and drink excessively.

    Most cases of central DI are idiopathic, meaning that they occur for no known reason; however, damage to the part of the brain that makes ADH can lead to DI. Cancer or trauma are two common known causes of central DI. A second uncommon form called nephrogenic DI results from impaired responsiveness of the kidney to the action of ADH. It is a rare, congenital condition and has occasionally been reported to be hereditary in a few instances.

    Excessive urination and thirst is a common clinical sign. The diagnostic tests recommended will help differentiate DI from these other conditions that can cause excessive thirst and urination:

  • Diabetes mellitus (excessive sugar in the blood)
  • Renal glycosuria (excessive sugar in the urine, but not diabetic)
  • Chronic kidney failure
  • Pyometra (infection of the uterus)
  • Hypercalcemia, a condition of excessively high calcium levels in the blood
  • Liver failure
  • Hyperadrenocorticism, also called Cushing's disease, a condition of overactive adrenal glands
  • Pyelonephritis, an infection of the kidneys
  • Hypokalemia (low potassium levels in the blood)
  • Hypoadrenocorticism, also called Addison's disease, a condition of underactive adrenal glands
  • Hyperthyroidism (excessive thyroid activity)
  • Acromegaly (excessive production of growth hormone)
  • Psychogenic polydipsia (excessive drinking due to psychological reasons, such as a change in the pet's environment

  • Veterinary Care should include diagnostic tests and subsequent treatment recommendations

    Diagnosis In-depth

    Diagnostic tests are mostly geared toward ruling out the more common causes of excessive thirst and urination. Once the common disorders are ruled out, specific tests for DI can be performed.

  • A complete medical history review and physical examination are important in determining the potential cause of excessive thirst and urination. This may include a request to quantify how much water the pet is drinking

  • A complete blood count to rule out pyometra (uterine infection)

  • A serum biochemistry panel to assess the function of the major organs and rule out many diseases like diabetes mellitus, chronic kidney failure, liver failure, high calcium, and low potassium

  • Urinalysis and urine culture to rule out kidney infection, diabetes mellitus, kidney failure, and other illnesses

  • X-rays or ultrasound, depending on the history and physical exam findings, to evaluate the kidneys, liver, adrenal glands, and uterus for potential diseases that could have similar signs as DI

  • A bile acid test to assess liver function

  • Specific tests of the adrenal gland to rule out overactivity or underactivity of these glands as possible causes of excessive thirst and urination

  • A thyroid hormone test to assess the status of the thyroid gland

  • The modified water deprivation test is the most important test for confirming a diagnosis of diabetes insipidus once all other causes of excessive thirst and urination have been ruled out. This is a labor intensive test that may require a full day of hospitalization.

    Treatment In-depth

  • Desmopressin acetate (also called DDAVP) is a synthetic form of the hormone ADH. It is the standard therapy for central DI. It comes in two forms: injection and nasal drops. The nasal spray can be transferred to a sterile eye dropper bottle and applied to the eye if the dog won't tolerate nasal drops. One to four drops administered once or twice a day usually controls the clinical signs.

  • Chlorpropamide may reduce urine output in some dogs, although results can be inconsistent. Severe forms of central DI often don't respond.

  • Thiazide diuretics – while it may seem paradoxical to give a dog with DI a diuretic to increase urine output, the net result is usually a reduction in overall urine output.

  • Salt restriction has a net effect of reducing urine output, and may be used sometimes as the sole therapy for central DI.        

    Therapy is not mandatory for DI as long as the pet has unlimited access to water, and is kept in an environment where constant urination is not a problem. This usually applies to outdoor pets. Therapy with DDAVP can be administered intermittently, when severe thirst and excess urination is especially undesirable, for example, if guests are visiting. Unrestricted access to water is absolutely imperative.

    Follow-up

    Optimal treatment for a pet with diabetes insipidus requires both home and professional care, with follow up being critical. Administer prescribed medications and alert your veterinarian if you are experiencing problems treating your pet. Follow up includes:

  • Periodic rechecks by your veterinarian, especially if the diabetes insipidus is suspected to be caused by a tumor affecting the part of the brain responsible for making ADH.

  • Seek immediate veterinary care if any illness develops that causes vomiting or causes the pet to reduce his water intake, as there is a risk of life-threatening dehydration if water is withdrawn from pets with DI for even a few hours.

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