Diabetes Insipidus Diagnosis
Since diabetes mellitus is much more frequent and because diabetes insipidus and diabetes mellitus do have symptoms which are similar, your doctor may believe that you have diabetes mellitus. But testing will show that his first thoughts were wrong. There are two common forms of diabetes insipidus which are central diabetes insipidus and neurogenic diabetes insipidus. Both of these types are caused by different problems.
If diabetes insipidus is the diagnosis after confirmation, the doctor will then need to resolve the type of diabetes insipidus you have as the treatment is different depending on which form of diabetes insipidus you have. This battery of tests will include a urinalysis, a test known as a fluid deprivation test and possibly an MRI.
Urinalysis
This is the chemical and physical examination of the urine. A person who has diabetes insipidus will have urine which is much less concentrated. The concentrations of waste and salt will be low while the water amount excreted will be very high. The urine concentration is also measured by comparing the weight between a specific amount of distilled water to the same amount from the urine sample (specific gravity) or by the amount of particles which are in a kilogram of water (osmolality).
Water deprivation test
You will need to stop fluid intake 2 to 3 hours before the time of the test. The doctor will measure changes in the weight of your body, urine composition as well as the amount of output when fluids have been withheld. The doctor might also measure the blood level of the hormone ADH which regulates the retention and output of urine.
Magnetic resonance imaging (MRI)
The MRI of the head area is a procedure using radio waves and magnets to create a detailed picture of the brain tissues. The doctor will be looking for any types of abnormalities in or around the pituitary gland.
If your doctor believes you have an inherited type of diabetes insipidus, he/she will examine your family history for incidents of polyuria (large amounts of urine). Your doctor may also suggest genetic screening.
