Diabetes insipidus (DI) is a condition characterized by excretion of large amounts of severely diluted urine, which cannot be reduced when fluid intake is reduced. It denotes inability of the kidney to concentrate urine. DI is caused by a deficiency of antidiuretic hormone (ADH), also known as vasopressin, due to the destruction of the back or “posterior” part of the pituitary gland where vasopressin is normally released from, or by an insensitivity of the kidneys to that hormone. It can also be induced iatrogenically by various drugs.

There are four (4) fundamentally different types of Diabetes Insipidus (DI).  Each has a different cause and must be treated in a different way.  These four forms are: Neurogenic, also known as central, hypothalamic, pituitary or neurohypophyseal is caused by a deficiency of the antidiuretic hormone, vasopressin. Nephrogenic, also known as vasopressin-resistant is caused by insensitivity of the kidneys to the effect of the antidiuretic hormone, vasopressin. Gestagenic, also known as gestational is also caused by a deficiency of the antidiuretic hormone, vasopressin, that occurs only during pregnancy. Dipsogenic, a form of primary polydipsia is caused by abnormal thirst and the excessive intake of water or other liquids.

How do you test for diabetes insipidus?

Usually your doctor will check your urine to see how much water is in it. He or she may also check your blood. Your doctor may give you a “water deprivation” test. During this test, you aren’t allowed to drink any liquids. The staff will weigh you, check your urine and blood every hour for several hours. If the results of the test show that you have diabetes insipidus, you will probably also have pictures taken of your brain with a CT (computed tomographic) scan or an MRI (magnetic resonance image). The scans can show problems in the brain.

The osmolality test is a snapshot of the number of solutes present in the plasma, urine, or stool. It is ordered to help evaluate the body’s water balance, its ability to produce and concentrate urine, to help investigate hyponatremia, to detect the presence of toxins such as methanol and ethylene glycol, and to monitor osmotically active drug therapies such as mannitol. It is also ordered to help monitor the effectiveness of treatment for any conditions found.

Why the Test is Performed?   

MRI provides detailed pictures of the brain and nerve tissues from multiple angles without obstruction by overlying bone. In fact, about 90% of all MRI scans are for brain or spine disorders.MRI is the procedure of choice for most brain disorders. MRI is particularly useful in brain and neurological disorders, because it can clearly show different types of nerve tissue. It provides clear pictures of the brainstem and posterior brain, which are difficult to view on CT scan. It is also useful for the diagnosis of demyelinating disorders. These are disorders such as multiple sclerosis, which cause destruction of the myelin covering of the nerve. MRI is a noninvasive procedure that can evaluate blood flow and the flow of cerebrospinal fluid (CSF). MRI can distinguish tumors or other lesions from normal tissues. MRI is sometimes used to avoid the dangers of angiography or of repeated exposure to radiation.

Risk factors:

Nephrogenic diabetes insipidus that is present at or shortly after birth usually has a genetic cause that permanently alters the kidneys’ ability to concentrate the urine. Nephrogenic DI usually affects males, though women can pass the gene on to their children

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