What is feline diabetes insipidus?

Diabetes insipidus is an extremely rare disease in cats. The most obvious symptoms of feline diabetes insipidus are excessive urination and excessive thirst, which are caused by irregular production or reaction of ADH (antidiuretic hormone). ADH is normally produced in the hypothalamus of the brain and stored in the pituitary gland. Without normal antidiuretic hormone production and response, the kidneys are unable to reabsorb water from the blood, forcing the cat to urinate excessively and drink more water to compensate.

Diabetes insipidus should not be confused with the more common form of diabetes insipidus in cats. Diabetes insipidus and diabetes both have symptoms of excessive thirst and excessive urination, but the causes of these symptoms (including treatment options) differ.

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 well to antidiuretic hormones.

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

Symptoms of feline diabetes insipidus

The most common symptoms of feline diabetes insipidus may include:

1. Polydipsia

2 , Excessive urination

3. Urinary incontinence caused by increased and frequent urination

4. Dehydration

5. Decreased appetite

6 , Weightlessness

7. Lethargy

Possible neurological abnormalities (seizures, disorientation and incoordination)

Causes of feline diabetes insipidus

There are two main causes of feline diabetes insipidus that can be treated, depending on the cause.

Central diabetes insipidus: a disease that occurs when the brain (especially the hypothalamus) cannot secrete enough antidiuretic hormone, or the pituitary gland cannot store antidiuretic hormone normally. Cats with CDI tend to be middle-aged and older pets.

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

Nephrogenic diabetes insipidus (NDI): A disease that occurs when the kidneys fail to respond appropriately to antidiuretic hormone secreted by the brain.

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

1. Drugs

2. Diseases such as Addison's disease, Cushing's disease, or pyometra

3. Kidneys Injury, such as infection, inflammation, urinary tract obstruction, or chronic kidney disease

4. Liver disease

5. Hypercalcemia

6. Electrolyte abnormalities

7. Leptospira infection

8. Hyperthyroidism

9. Idiopathic (unknown)

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

How Veterinarians Diagnose Cat Diabetes Insipidus

When diagnosing feline diabetes insipidus, your veterinarian will start with a physical examination and an extensive medical history. They will want to perform the same lab work and tests that are also done to identify the common (but vague) symptoms of excessive urination and excessive thirst in cats. This laboratory work may include:

1. Blood chemistry

2. Complete blood count

3. Urine culture analysis

4. Adrenocorticotropic hormone stimulation test

5. Low-dose dexamethasone suppression test

6. Serum bile acids

7. Thyroid function test

This level of feline lab work will help rule out more common conditions such as kidney disease, hyperthyroidism, or diabetes.

It is worth noting that a veterinarian once performed a water shortage test to diagnose feline diabetes insipidus. However, this test resulted in extremely sick cats—especially those with other serious illnesses. This test is largely unsuitable for diagnosing diabetes insipidus in cats due to the risks shown in previous cases.

Treatment of Feline Diabetes Insipidus

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

For cats diagnosed with CDI, they can continue to take desmopressin throughout their lives to reduce symptoms. It is important that they have access to water around the clock and can urinate freely. Your veterinarian may recommend additional supportive treatment options.

Pet parents should monitor cats treated with desmopressin for signs of overhydration, including symptoms such as vomiting and diarrhea, difficulty breathing, or changes in mental status.

For cats diagnosed with NDI, it can be cured if your veterinarian can treat the main underlying disease. Remember, there is no cure for unexplained NDI and it can only be reversed after the underlying disease is identified and treated. If the underlying disease is chronic, it may also trigger NDI recurrence.

Medical treatments for feline diabetes insipidus

The veterinarian will test a drug called desmopressin. This medication is a synthetic version of antidiuretic hormone that replaces this hormone. Prior to administration, urine osmolarity, i.e. the number and concentration of particles dissolved in the urine, will be measured before the drug is introduced.

After dosing is in the cat's system, pet parents will be asked to measure the cat's urine output and water intake for several days and continue to monitor its water and urination. Once the pet parent collects the urine sample, the veterinarian will re-perform the urine test.

A significant decrease in water intake and a urine concentration greater than 50% are consistent with the diagnosis of CDI.

Cats with NDI virus will not get better (which is why NDI virus is suspected) and more testing may be necessary.

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

Recovery and Treatment of Diabetes Insipidus in Felines

The prognosis for diabetes insipidus is usually good, depending on the underlying disease.

NDI can be cured, while CDI usually cannot be cured unless it is due to trauma or is only temporary.

Cats with some forms of diabetes insipidus can live relatively normal lives if their owners can control the side effects of thirst and urination.

Cats with diabetes insipidus, especially those that are untreated, must always have access to water. Otherwise, severe dehydration, coma, and death may occur.

For pets taking desmopressin or other medications, they will most likely need periodic laboratory tests to evaluate kidney function, urine concentration, and electrolytes.