Diabetes Insipidus in Cats

What is Diabetes Insipidus in Cats?

Diabetes insipidus is an extremely rare condition in cats. The most obvious symptoms of diabetes insipidus in cats are excessive urination and excessive thirst, due to an irregular production or response to ADH (Anti-Diuretic Hormone). ADH is normally produced in the hypothalamus of the brain and stored in the pituitary gland. Without normal ADH production and response, the kidneys are prevented from reabsorbing water from the bloodstream, forcing the cat to urinate excessively and drink much more water to compensate. 

Diabetes insipidus should not be confused with the much more common diabetes mellitus in cats. Both diabetes insipidus and diabetes mellitus share the symptoms of excessive thirst and excessive urinating, however the causes of these conditions — including treatment options — vary.

There are two forms of Diabetes Insipidus:

• Central Diabetes Insipidus (CDI): the hypothalamus does not produce any or enough ADH.

• Nephrogenic Diabetes Insipidus (NDI): the kidneys do not respond appropriately to ADH.

Your veterinarian will want to rule out any other conditions before treating diabetes insipidus. Fortunately, some types of diabetes insipidus are treatable, and many cats can lead normal, healthy lives.

Symptoms of Diabetes Insipidus in Cats

The most common symptoms of diabetes insipidus in cats may include:

• Excessive thirst

• Excessive 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 Cats

There are two main causes for diabetes insipidus in cats which may be treatable, depending on the cause.

Central Diabetes Insipidus (CDI): A condition that occurs when the brain, specifically the hypothalamus, does not secrete enough ADH, or the pituitary gland is unable to store it properly. Cats with CDI tend to be middle-aged and senior pets. 

Central diabetes insipidus in cats can be caused by a congenital defect, head trauma (such as a car accident or injury), cancer within a specific part of the brain or for reasons unknown.

Nephrogenic Diabetes Insipidus (NDI): A condition that occurs when the kidneys cannot respond appropriately to the ADH secreted by the brain.

Acquired NDI in cats has many causes, and there is no known breed, age, or gender predisposition to secondary NDI. Causes of acquired NDI include:

• Medications

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

• Kidney damage, such as infection, inflammation, urethral blockage or chronic kidney disease

• Liver disease

• High calcium

• Electrolyte abnormalities

• Leptospirosis infection

• Hyperthyroidism

• Idiopathic (unknown)

If a cat is diagnosed with NDI a veterinarian will want to treat the underlying condition, if possible, to reverse the condition.  

How Veterinarians Diagnose Diabetes Insipidus in Cats

When diagnosing diabetes insipidus in cats, your veterinarian will start with a physical exam and an extensive history. They will want to run the same lab work and testing that is also ordered to determine the common (but vague) symptoms of excessive urination and excessive thirst in cats. This lab work may include:
 

• Blood chemistry

• Complete blood count

• Urinalysis with culture

• ACTH stimulation test

• Low-Dose Dexamethasone Suppression Test

• Serum bile acids

• Thyroid function tests

This level of lab work in cats will help to rule out a more common condition such as kidney disease, hyperthyroidism or diabetes in cats.

It’s important to note at one time veterinarians ran a water deprivation test to diagnose diabetes insipidus in cats. However, this test led to cats becoming extremely ill—especially those with other serious diseases. Due to the risks shown in previous cases, this test is largely out of favor for diagnosing diabetes insipidus in cats.

Treatment of Diabetes Insipidus in Cats

Treatment will depend on whether the cat is diagnosed with the CDI or NDI form of diabetes insipidus.

For cats diagnosed with CDI, they can continue to take the Desmopressin for the duration of its life to reduce symptoms. It is important they are allowed 24/7 access to water, and can urinate freely. A veterinarian may recommend additional supportive therapy options.

Pet parents should monitor cats treated with Desmopressin for signs of overhydration, which includes symptoms such as vomiting and diarrhea, difficulty breathing or changes in mentation.

For cats diagnosed with NDI, it can be cured if the veterinarian is able to treat the primary underlying disease. Keep in mind, there is no cure for NDI of unknown causes, it can only be reversed if the primary disease is identified and treated. If the underlying condition is chronic, it may also trigger NDI relapses.

Medication Treatment for Diabetes Insipidus in Cats

Veterinarians will run a trial test with a drug called Desmopressin. This drug is a synthetic version of ADH that acts a replacement for the hormone. Before the drug is given, urine osmolality, or how many particles are dissolved in the urine and concentration will be measured before the drug is introduced.

After the drug is administered and in the cat’s system, a pet parent will be asked to measure the urine output and water intake from the cat for a few days and continue to monitor its water and urination. Once urine samples are collected by the pet parent, your veterinarian will re-run the urine tests.

A significant decrease in water intake and an increase in urine concentration of more than 50 percent are consistent with a diagnosis of CDI.

Cats with NDI will not improve (which is how the NDI form will be suspected) and more testing may be necessary.

Advanced imaging, such as MRI and CT scans, may also be used to help the vet evaluate the brain for cancer, lesions or trauma.

Recovery and Management of Diabetes Insipidus in Cats

The prognosis for diabetes insipidus is generally good, depending on the underlying disorder.

NDI can be cured, while CDI is usually not curable unless the cause is due to trauma or is only temporary.

Cats can live relatively normal lives with some forms of diabetes insipidus if the side effects of thirst and urination are manageable for the pet parent.

Cats with diabetes insipidus, especially those untreated, must always have access to water. If not, severe dehydration, stupor, coma, and death may occur.

For pets on Desmopressin or other medications, they will most likely require lab work on a regular basis to evaluate kidney function, urine concentration and electrolytes.