Alternative names
Diabetes insipidus - nephrogenic; Acquired nephrogenic diabetes insipidus;

Definition
Nephrogenic diabetes insipidus is a disorder characterized by the passage of large volumes of urine due to a defect of the kidney tubules. See also diabetes insipidus-central.

Causes, incidence, and risk factors

Antidiuretic hormone (ADH; vasopressin) is a hormone produced in the hypothalamus of the brain. It concentrates the urine by triggering the kidneys to reabsorb water into the blood stream rather than excreting water into the urine.

Nephrogenic diabetes insipidus involves a defect in the kidney tubules (the portion of the kidneys that causes water to be excreted or reabsorbed).

The specific kidney defect is usually a partial or complete failure of special receptors located on or within the kidney tubules to respond to ADH, the hormone that transmits the instruction to concentrate the urine to the inside of the cells.

Excessive amounts of water are excreted with the urine, producing a large quantity of very dilute urine. There is little or no response to vasopressin, even though the blood level of this hormone is higher than normal.

If thirst mechanisms are normal and adequate fluids are consumed, there are no significant effects on the fluid and/or electrolyte balance of the body. If inadequate fluids are consumed, the high urine output may cause dehydration and high blood sodium.

Nephrogenic DI is a rare disorder. It may be present at birth as a result of a sex-linked defect (congenital nephrogenic DI) that usually affects men, although women can pass the gene on to their children.

Most commonly, nephrogenic diabetes insipidus is an acquired disorder. Precipitating factors include drugs (lithium, demeclocycline, amphotericin B), electrolyte disorders (high calcium or low potassium levels), and urinary obstruction.

Symptoms

 
• Excessive thirst (may be intense or uncontrollable, with a craving for ice water)  
• Excessive urine volume (may exceed 3 to 15 liters per day)

Inadequate fluid consumption can result in:

 
• Dehydration       o Dry skin       o Dry mucous membranes       o Sunken appearance to eyes       o Sunken fontanelles (soft spot) in infants  
• Fatigue, lethargy  
• Headache  
• Irritability  
• Low body temperature  
• Muscle pains  
• Rapid heart rate  
• Weight loss

Signs and tests
Examination may indicate dehydration and/or shock if fluid intake is inadequate. The pulse rate may be rapid, with a low blood pressure present. The most significant indication of diabetes insipidus is persistent high urine output regardless of fluid intake.

Signs associated with high urine output are:

 
• High serum osmolality  
• Low urine osmolality  
• Normal or high ADH levels  
• The kidneys not making a more concentrated urine when the person is given ADH

This disease may also alter the results of the following tests:

 
• Urine specific gravity  
• Urine concentration test  
• Urine 24h volume  
• Serum sodium

Treatment

The goal of treatment is to regulate fluid levels in the body.

All cases should be treated with consistently high fluid intake. The volume of fluids consumed should approximately equal the volume of urine produced.

Reduction or discontinuation of medications that may cause nephrogenic DI may improve symptoms.

Hydrochlorothiazide may improve symptoms. This may be used alone or in combination with other medications, including indomethacin. Although this medication is a diuretic (these medications are usually used to increase urine output), hydrochlorothiazide can actually reduce the urine output for people with nephrogenic DI.

This medication works by causing sodium and water to be excreted in the early part of the renal tubules (the proximal tubules).

This leaves less fluid available for the late portion of the kidney (distal tubule) to excrete - this is the portion affected by nephrogenic DI - and thus it limits the total volume of urine that can be excreted.

Expectations (prognosis)
Congenital nephrogenic DI is a chronic condition requiring lifelong treatment. Acquired nephrogenic DI may be short-term or long-term.

Complications

 
• Severe dehydration, shock (if inadequate fluid intake)  
• Hypernatremia (high blood sodium)  
• Dilation of the ureters and bladder

Calling your health care provider
Call your health care provider if symptoms indicate diabetes insipidus may be present.

Prevention
There is no known prevention for congenital nephrogenic diabetes insipidus. Treatment of causative disorders may prevent some cases of acquired nephrogenic DI. Medications should only be used under the supervision of the health care provider.

Medical Encyclopedia

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.