What is diabetes insipidus?
Diabetes insipidus is a rare dog disease that results from a disorder in the regulation of water metabolism and has no connection with diabetes mellitus,
It exists in two forms:
- central or pituitary diabetes insipidus, linked to a lack of antidiuretic hormone (ADH) secretion,
- renal or nephrogenic diabetes insipidus, caused by a loss of sensitivity of the kidney to ADH.
Zoom on DHA and its role
Antidiuretic hormone (ADH) is also called vasopressin. It is made by the hypothalamus and then stored and released into the bloodstream by the pituitary gland, two glands located in the animal's brain. As its name suggests, ADH is involved in the reabsorption of water by the dog's body by acting on the terminal part of the renal tubule. Its secretion is normally stimulated by a decrease in blood volume or by an increase in osmotic pressure of blood plasma (a concentration of blood constituents). These physiological variations are picked up by osmoreceptors and baroreceptors in the brain and blood vessels.
We also sometimes speak of psychogenic diabetes insipidus to designate potomania in dogs. It is a disease of psychological origin that pushes the dog to drink a lot. This disease is a behavioral disorder that is therefore not caused by any damage to the brain or kidney.
What causes diabetes insipidus in dogs?
Central diabetes insipidus can have the following origins:
- a congenital anomaly and/or whose origin is not precisely known (idiopathic central diabetes insipidus),
- a brain tumor,
- head trauma,
- taking certain medications,
- low blood oxygen levels,
- an increase in the percentage of red blood cells in relation to total blood volume.
Nephrogenic diabetes insipidus may be related to:
- a hereditary disease in the Siberian Husky,
- a metabolic abnormality,
- an endocrine disorder (hypercorticism, hyperthyroidism, ),
- liver failure,
- various kidney diseases in dogs,
- a serious infection of the uterus in an unsterilized female dog.
Diabetes insipidus: symptoms in dogs
When a dog suffers from diabetes insipidus, the lack of ADH or lack of response of the renal tubule to ADH causes the dog's urine to be too dilute, which leads to an increase in the amount of emitted urine (polyuria) and very strong thirst (polydipsia) to compensate for these significant water losses.
These symptoms are often associated with:
- a state of dehydration in the animal,
- noctiuria, i.e. nocturnal urine emissions causing uncleanliness, and which can be confused with urinary incontinence,
- clinical signs related to the origin of the condition: neurological disorders when diabetes insipidus is caused by brain damage or symptoms linked to endocrine or renal disorders in the case of nephrogenic diabetes insipidus.
Diagnosis of diabetes insipidus
Diagnosis of diabetes insipidus in dogs is carried out in several stages. It requires first to carry out a urine and blood analysis and then, in a second step, to a water restriction test. This test consists of restricting the amount of drink in order to observe if the dog concentrates its urine sufficiently.
Once the type of diabetes insipidus (central or nephrogenic) has been determined using this test, the veterinarian sets out to find its origin. To do this, he generally carries out additional examinations such as:
- a brain scan in case of central diabetes insipidus,
- additional blood and urine tests, abdominal ultrasound and/or kidney biopsy in case of nephrogenic diabetes insipidus.
What treatment for diabetes insipidus in dogs?
The treatment of diabetes insipidus in dogs differs depending on the cause diagnosed by the veterinarian.
In the absence of an identified cause and when it is established that the diabetes insipidus is central, the dog may receive treatment based on desmopressin, a structural analog of synthesis of the natural antidiuretic hormone.
Other treatments based on thiazide diuretics are also possible. They have the effect of passively stimulating the reabsorption of water.
If diabetes insipidus is of psychological origin, behavioral therapy generally associated with the prescription of anxiolytic drugs is appropriate.