Diabetes Insipidus in Dogs

What is Diabetes Insipidus in Dogs?

Diabetes insipidus is a rare condition in dogs. The condition is caused by the inability to make or react to antidiuretic hormone (ADH) which forces excessive urination and subsequent thirst. This hormone, produced in the hypothalamus area of the brain, and stored in the pituitary gland, helps regulate water conservation. If ADH is not readily available or if the kidneys are not functional, water is lost through the urine. This leads to large urine volume and secondary increased thirst.

Diabetes insipidus is not the same as the common condition, diabetes mellitus in dogs. Both diabetes insipidus and diabetes mellitus share the symptoms of excessive thirst and urinating. But the conditions are treated very differently.

There are two forms of diabetes insipidus in dogs:

• Central Diabetes Insipidus (CDI) in dogs occurs when the hypothalamus does not produce any or enough ADH.

• Nephrogenic Diabetes Insipidus (NDI) in dogs occurs when the kidneys do not respond appropriately to ADH.

Both conditions are extremely rare. The hallmark signs of diabetes insipidus are polyuria (increased urination) and polydipsia (increased thirst). Since there are dozens of more common diseases that can cause the same clinical signs, your veterinarian will want to rule out these disorders first. 

Fortunately, some forms of diabetes insipidus are treatable, meaning dogs diagnosed with the condition will lead normal lives.

Symptoms of Diabetes Insipidus in Dogs

The most typical symptoms of diabetes insipidus in dogs include: 

• Excessive thirst and urination

• Incontinence due to increased and frequent urination

• Dehydration

• Decreased appetite

• Weight loss

• Lethargy

• Possible neurological abnormalities (seizures, disorientation, and incoordination)

Causes of Diabetes Insipidus in Dogs

Diabetes insipidus in dogs can be caused two ways:

Central Diabetes Insipidus (CDI): occurs when the hypothalamus within the brain, does not produce enough ADH, or the pituitary gland is unable to store it properly. This is more commonly seen in senior or middle-aged dogs.

Causes of CDI in dogs include:

• Congenital defect (born with condition, and is rare)

• Head trauma (car accident, falling injury, bite wound, oxygen deprivation, etc.)

• Cancer that affects this specific part of the brain

• Idiopathic (unknown cause)

Nephrogenic Diabetes Insipidus (NDI): occurs in dogs when the kidneys cannot react to the ADH that is produced from the brain. There are primary and secondary forms of NDI.

Primary NDI is when a dog is born with a deficiency in ADH receptors in the kidney. Veterinarians usually diagnose primary NDI in dogs under one year of age. Primary NDI seems to occur in German Shepherds, Miniature Poodles and Siberian Huskies, although it is unknown if there is a genetic cause.

Secondary or acquired NDI has many causes including:

• Certain medications

• Diseases such as Addison’s disease, Cushing’s disease or pyometra

• Kidney damage (infection, inflammation, urethral blockage or chronic kidney disease)

• Liver disease

• High calcium

• Electrolyte abnormalities

• Leptospirosis infection

• Idiopathic (unknown)

How Veterinarians Diagnose Diabetes Insipidus in Dogs

A veterinarian will conduct the same lab work and testing to determine the cause of symptoms for excessive thirst and urination in dogs. This may include the following:

• Complete blood count

• Urinalysis, with culture

• Adrenocorticotropic hormone (ACTH) stimulation test for Addison’s disease

• Low Dose Dexamethasone Suppression Test primarily tests for Cushing’s disease

• Serum bile acids analyze liver function

• Thyroid function tests to determine hypothyroid disease or an underactive thyroid

These tests will help rule out more common conditions that lead to polydipsia and polyuria including kidney disease or Cushing’s disease.

An outdated test, called a water deprivation test, was previously used by veterinarians to diagnose the condition. Dogs given this test would become critically ill, especially those with other serious conditions, and because of this reaction the test has been removed from most offices.

Treatment of Diabetes Insipidus in Dogs

Treatment for diabetes insipidus in dogs will depend on what is determined during diagnosis, and if the dog has CDI or NDI.

CDI Treatment

Dogs diagnosed with CDI may continue to take Desmopressin to help reduce symptoms. This medication is available in both nasal and oral forms. Pet parents should monitor dogs treated with Desmopressin for signs of overhydration which includes vomiting and diarrhea, difficulty breathing or changes in mentation.

CDI in dogs is rarely cured but can be managed. Veterinarians may treat dogs with Desmopressin and other supportive therapy options.

NDI Treatment

NDI can be cured if vets can identify and treat the primary underlying disease. However, there is no specific therapy to cure NDI on its own.

Medication Treatment for Diabetes Insipidus in Dogs

More commonly, a trial with the drug Desmopressin is used as a safer alternative. Desmopressin serves as a synthetic version of ADH and can act as a replacement to the hormone. Veterinarians will likely only attempt this trial test if they have ruled out all other possible conditions for excessive urination and thirst in dogs.

Once the drug is given, a pet parent will be asked to measure urination output and water consumption for a set number of days and submit urine for testing to the veterinarian before and after.

A significant decrease in water intake and an increase in urine concentration of more than 50 percent are consistent with a diagnosis of CDI. A dog with the NDI form of this condition will not show signs of improvement.

Up to 40 percent of dogs with CDI have a pituitary tumor, so these tests are valuable in cases of CDI. A vet may recommend advanced imaging including MRI and CT scans, which are used to help the vet evaluate the brain for cancer, lesions or trauma.

Recovery and Management of Diabetes Insipidus in Dogs

The prognosis for both CDI and NDI forms is typically good, depending on the underlying disorder.

NDI can be cured with treating the underlying disease or disorder, while CDI is usually not curable. The only types of CDI that can be cured are those that are transient or trauma-related and allow the brain’s anatomy to return to normal. NDI may be controlled by treating the underlying disease, however, if that disease is chronic, it may also lead to relapses of NDI. Dogs can live near-normal lives with some forms of diabetes insipidus — if the side effects of thirst and urination are not intolerable to pet parents.

Dogs with diabetes insipidus, especially those who are untreated, must always have access to water. If not, severe dehydration, stupor, coma and death can occur.

Follow-up lab work will likely be recommended for any pet on Desmopressin, or additional medications, to ensure kidney function and other organs are working properly.