Evaluation and Management of Diabetes Insipidus

Title: Evaluation and Management of Diabetes Insipidus
Author: Adam, MD, Patricia
Publisher: American Family Physician
Date Published: May 01, 1997
Reference Number: 2
Diabetes insipidus is an uncommon condition characterized by polyuria and polydipsia. The symptoms and biochemical changes of this condition result from either a lack of antidiuretic hormone or renal insensitivity to its effect. Failure to produce or release antidiuretic hormone may result from cranial pathology, including trauma and surgery. The renal insensitivity to antidiuretic hormone that occurs in patients with nephrogenic diabetes insipidus may be caused by genetic factors, drugs (especially lithium) or specific disease processes. Patients may compensate for polyuria and nocturia by excessive water intake but show marked decreases in urine specific gravity and osmolality. Patients with severe and uncompensated symptoms develop marked dehydration, neurologic symptoms and encephalopathy. The water deprivation test is useful in diagnosing diabetes insipidus and in differentiating neurogenic from nephrogenic cases. Neurogenic diabetes insipidus may respond to nasal administration of desmopressin. Nephrogenic diabetes insipidus requires good hydration and monitoring of body chemistry. Thiazides and amiloride may relieve symptoms.

This translation by the NDI Foundation is to assist the lay reader. To provide a clear, accessible interpretation of the original article, we eliminated or simplified some technical detail and complicated scientific language. We concentrated our translation on those aspects of the article dealing directly with NDI. The NDI Foundation thanks the researchers for their work toward understanding and more effectively treating this disorder.
© Copyright NDI Foundation 2007 (JC)

People with diabetes insipidus (DI) either do not produce enough of the antidiuretic hormone, vasopressin, or their kidneys do not read the message delivered by vasopressin. They cannot, therefore, concentrate their urine and thus suffer from polyuria (chronic, excessive urination) and polydipsia (chronic, excessive thirst). There are two types of DI: neurogenic (originating in the nervous system) or nephrogenic (having its source in the kidney). DI is a rare disease, the neurogenic form being more common than the nephrogenic form.

Neurogenic DI can appear for unknown reasons; it can arise after a trauma to the brain such as an accident, surgery, cancer or tumor; it can also be inherited. Nephrogenic DI is often inherited. It can also be acquired as a result of a metabolic disorder, kidney disease or through using prescribed drugs such as lithium. About 25% of the time, physicians can\'t find a cause for DI. They call this idiopathic DI. It is invariably permanent, affects males more often than females, and appears at the median age of 16.

Treating physicians should consider diagnosing for DI if a patient complains of constant thirst and frequent urination. They should test the patient\'s blood serum and urine as DI results in dilute urine and a serum concentration that is a little above normal but that will rise drastically if the patient is deprived of fluids. Neurogenic DI can develop suddenly, often following a head trauma. Nephrogenic DI, if inherited, can manifest the first week of life and must be diagnosed and treated early to prevent possible physical and mental harm brought about by episodes of severe dehydration.

Since the symptoms are the same, physicians use the water deprivation test on patients to differentiate between neurogenic and nephrogenic DI. In a water deprivation test the patient isn\'t allowed to drink any liquids and they have hourly blood and urine samples. The physician looks closely at the association between urine and serum concentrations and the antidiuretic hormone level. Urine concentrations that remain low as serum concentrations rise are suggestive of DI. People with neurogenic DI will respond to injections of synthetic antidiuretic hormone (DDAVP), and their ability to concentrate urine will improve, whereas patients with nephrogenic DI will not respond as well. Further diagnosis might include taking x-ray-like pictures of the patient\'s brain with computed tomography (CT) and magnetic resonance imagery (MRI).

Patients with neurogenic DI are often treated successfully with DDAVP. Patients with partial pituitary diabetes may respond to chlorpropamide, clofibrate or carbamazepine. In patients with nephrogenic DI, DDAVP is ineffective, but certain diuretics such as thiazides or amiloride may help, as may a low-salt, low-protein diet.