Diabetes insipidus is often called Water Diabetes
Diabetes Insipidus not the disease that most people think of when they hear the word diabetes. For that, see diabetes mellitus.
Symptoms of Diabetes Inspidius
Diabetes insipidus is characterised by the production of excessive dilute urine and an extreme thirst in the patient. These can also be symptoms of diabetes mellitus, but the two diseases have very different causes. Diabetes insipidus is sometimes called the “water diabetes” (as opposed to diabetes mellitus which is called “sugar diabetes”).
One of the roles of the kidneys is to filter the blood that passes through them, and collect the water and dissolved toxins. This fluid will eventually become the urine, and is the way the body gets rid of a number of waste products from the body. However, before urine is produced and passed to the bladder, the kidneys need to re-absorb water from the filtrate so that the body does not dehydrate.
Causes of Diabetes Insipidus (DI)
Diabetes insipidus results when the kidneys are unable to re-absorb the excess water from the urine. The hormone in the body that is responsible for re-absorption of water is antidiuretic hormone (ADH). This is sometimes called vasopressin. Diabetes insipidus can result when either the pituitary gland is not able to produce sufficient ADH (“pituitary diabetes insipidus”), or the kidneys themselves are unable to respond to levels of ADH in the blood (“nephrogenic diabetes insipidus”).
Pituitary DI is caused by damage to the posterior pituitary (where the ADH is produced) by, for example:
- head injury
The Nephrogenic DI (note: nephrogenic gets its name from “nephron” which are tubes found in the kidney responsible for water reabsorption) can be inherited but can also result from:
- kidney disease
Diagnosis of Diabetes Insipidus
The diagnosis of Diabetes Insipidus can include any of the following:
- Urine analysis – electrolyte levels.
- Blood tests – blood electrolyte measurements.
- Water deprivation tests – helps determine the type of DI. This test measures body weight, urine output and composition of urine during the test period when fluids are withheld from the patient.
Treatment of Diabetes Insipidus
The underlying cause of the disease needs to be treated if possible. e.g. if ADH is too low, patients can take ADH tablets or nasal spray.
Where damage is irreversible, treatment involves increasing excess fluid to balance the urine production, and possibly taking drugs to reduce urine excretion.
Diabetes Insipidus does not usually cause long term problems if treated.