Thursday, October 26, 2006

Diabetes insipidus (DI)

Diabetes insipidus (DI) 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), or by an insensitivity of the kidneys to that hormone.

Symptoms of Diabetes insipidus (DI) :

Excessive urination and extreme thirst (especially for cold water) are typical for DI. Symptoms of diabetes insipidus are quite similar to those of untreated diabetes mellitus, with the distinction that the urine is not sweet and there is no hypergyclemia (elevated blood glucose). Blurred vision is a rarity.

The extreme urination continues throughout the day and the night. In children, DI can interfere with appetite, eating, weight gain, and growth as well. They may present with fever, vomitus, or diarrhea.

Adults with untreated DI may remain healthy for decades as long as enough water is drunk to offset the urinary losses. However, there is a continuous risk of dehydration.

How to Diagnosis Diabetes insipidus (DI) ?

In order to distinguish DI from other causes of excess urination, blood glucose, bicarbonate and calcium need to be tested. Electrolytes can show substantial derangement; hypernatremia (excess sodium levels) are common in severe cases. Urinalysis shows low electrolyte levels, and measurement of urine osmolarity (or specific gravity) is generally low.

A fluid deprivation test helps determine whether DI is caused by:
- excessive intake of fluid
- a defect in ADH production
- a defect in the kidneys' response to ADH

This test measures changes in body weight, urine output, and urine composition when fluids are withheld. Sometimes measuring blood levels of ADH during this test is also necessary.

To distinguish between the main forms, desmopressin stimulation is also used; desmopressin can be taken by injection, a nasal spray, or a tablet. While taking desmopressin, a patient should drink fluids or water only when thirsty and not at other times, as this can lead to sudden fluid accumulation in central nervous system. If desmopressin reduces urine output and increases osmolarity, the pituitary production of ADH is deficient, and the kidney responds normally. If the DI is due to renal pathology, desmopressin does not change either urine output or osmolarity.

If central DI is suspected, testing of other hormones of the pituitary, as well as magnetic resonance imaging (MRI), is necessary to discover if a disease process (such as a prolactinoma) is affecting pituitary function.

Habit drinking (in its severest form termed psychogenic polydipsia) is the most common imitator of diabetes insipidus at all ages. While many adult cases in the medical literature are associated with mental disorders, most patients with habit polydipsia have no other detectable disease. The distinction is made during the water deprivation test, as some degree of urinary concentration above isosmolar is eventually obtained before the patient becomes dehydrated.

Treatment of Diabetes insipidus (DI)

Central DI and gestational DI respond to desmopressin. In dipsogenic DI, desmopressin is not usually an option.

Desmopressin will be ineffective in nephrogenic DI. Instead, the diuretic hydrochlorothiazide (HCT or HCTZ) or indomethacin can improve NDI; HCT is sometimes combined with amiloride to prevent hypokalemia. Again, the patient should be reminded only to drink fluids when thirsty, and not at other times.

Even if untreated, DI does not cause death or reduce life expectancy unless the patient gets into a situation in which he or she cannot get an adequate supply of drinkable water.

Read more:

- Natural Diabetes Cure

- Why Low Blood Sugar Affects The Brain?