Nephrogenic Diabetes Insipidus

Nephrogenic diabetes insipidus, also known as Acquired Nephrogenic Diabetes Insipidus (ANDI) and Congenital Diabetes Insipidus is a form of diabetes insipidus which is due to the pathology of the kidney. This is in contrast to the central and Neurogenic DI which are due to insufficient levels of ADH or Anti diuretic hormone. Nephrogenic diabetes insipidus is caused by improper response of the kidneys to ADH and this leads to disability of the kidney to concentrate the urine by removing the water. Defect in the small tubes or tubules in the kidneys causes the patient to pass large amounts of urine. In normal persons, the tubules allow water to be removed from the kidneys and returned into the blood, without leaking the urine.

Causes of Nephrogenic Diabetes Insipidus

NDI occurs when the kidney tubules do not respond to a chemical in the body called ADH, also called vasopressin. It is ADH which tells the kidneys to make the urine more concentrated. Due to this, the kidneys release excessive amount of water into the urine and produce large quantity of very dilute urine. NDI is rare. Congenital diabetes insipidus is present during birth. Women can also pass this gene to their children. Other possible reasons of NDI are blockage in the urinary tract, low potassium levels, high calcium levels and use of certain drugs like lithium, demeclocycline, and amphotericin B.

Signs and symptoms of NDI

Intense and uncontrollable thirst and craving to drink ice water.
Large amounts of urine, usually 3 to 15 liters a day.
If sufficient intake of water is not done this could result in dehydration, dry mucous membranes, dry skin, sunken appearance of eyes, and sunken soft spot in infants. Other symptoms of inadequate fluids intake include fatigue, muscle pains, rapid heart rate weight loss.

A physical examination by a doctor would reveal low blood pressure, rapid pulse, shock and signs of dehydration. Diagnostic tests would reveal:

Osmolality of high serum
High urine output
Kidneys do not concentrate when the person is given ADH
Low urine osmolality and
Normal or high ADH levels.

Other diagnostic tests that are done include Serum sodium, 24-hour urine volume, Urine concentration test and Urine specific gravity

Treatment for Nephrogenic Diabetes Insipidus

Patients are normally given large amounts of fluids as the goal of treatment is to control the body's fluid levels. Amount of fluid given is equal to the amount of urine produced. Not keeping up with the fluid can lead to dehydration or electrolyte imbalance. Sometimes NDI is caused due to certain medication, and therefore stopping the medicines may improve symptoms. Hydrochlorothiazide may improve symptoms. This is prescribed alone or in combination with other medications. Although hydrochlorothiazide is a diuretic, it can actually reduce urine output for people with NDI. Some treatments which can reduce the symptom of nephrogenic diabetes insipidus are low salt, low protein diet and NSAIDs.

Diabetes Insipidus

Diabetes Insipidus or DI has nothing to do with diabetes mellitus or sugar diabetes. Diabetes insipidus is a condition that is characterized by intense thirst and polyuria or excretion of large amounts of urine. In sharp contrast to diabetes mellitus which results in sweet tasting urine, diabetes insipidus creates watery, flavor-free urine.

DI is a condition that occurs when the kidneys cannot conserve water when they perform their function of filtering blood. In other words, DI is a condition in which the body cannot retain enough water, a peculiar condition as the patient is excessively thirsty and excretes large amounts of extremely diluted urine. Significantly, a reduction in fluid intake does not reduce amounts and consistency of urine excretion. About 1 in every 25,000 people is affected by this condition in the US.

Diabetes Insipidus Classification

Neurogenic Diabetes Insipidus, when there is a deficiency of ADH (Anti Diuretic Hormone)
Nephrogenic Diabetes Insipidus, when kidneys are insensitive to ADH and
Gestational Diabetes Insipidus, which is very rare DI that occurs during pregnancy.

Antidiuretic hormone, ADH, also called vasopressin, is produced in the hypothalamus region of the brain. Lack of ADH causes central diabetes insipidus. Similarly, DI caused by a failure of kidneys to respond to ADH is called nephrogenic diabetes insipidus.

Causes and symptoms of central diabetes insipidus

Any damage to the pituitary gland as a result of possible head injury, infection, loss in the supply of blood to the gland, surgery and tumor can cause central diabetes insipidus. In some cases, it could be hereditary. Symptoms of DI are excessive thirst and excessive urination. Other common symptoms include Nocturia, bed wetting and feeling run down.

Diagnosis of Diabetes Insipidus

MRI of the head, urine analysis and urine output are the diagnostic tests performed to detect DI. Water deprivation test is done, when the patient stops drinking liquids for about two to three hours before starting the test. The doctor measures the alterations in body weight and urine output and composition. Urine analysis is done when the physical chemical content of urine is examined. If urine water content is high and salt and waste concentrations are low, then the patient suffers diabetes insipidus. ADH hormone test after the water deprivation test is done, and the doctor gives a small dose of ADH usually in the form of injection, to study how the patient reacts to the hormone. Genetic screening is recommended if an inherited form of DI is suspected.

Treatment of DI

Vasopressin, either as tablets or as nasal spray is prescribed for central diabetes insipidus. As such, if treated, diabetes insipidus does not cause severe problems or reduce life expectancy. To combat the dehydration problem caused by DI, enough fluids should be consumed. This will offset the effects caused on body fluid or salt balance. If enough fluid is not taken, it can lead to dehydration and electrolyte imbalance.