Definition
Nephrogenic diabetes insipidus (NDI) is a kidney disorder characterized by the kidney’s inability to respond to the antidiuretic hormone, arginine vasopressin (AVP). In NDI, the proper amount of water cannot be reabsorbed. This water, which is meant for and needed by the body, is instead voided in large quantities as dilute urine, leaving NDI patients chronically thirsty and in danger of dehydration. (The urine is called dilute because it has a high ratio of water to particles – such as minerals and salts – due to the unabsorbed water.) NDI patients require a steady supply of water to alleviate their thirst and prevent dehydration. NDI may be either acquired or heriditary (congenital).
Sometimes people confuse NDI with another type of diabetes insipidus called central diabetes insipidus (CDI), or, as it is more accurately called, pituitary DI. (Pituitary DI is also sometimes referred to as neurogenic DI or neurohypophyseal DI.) Though pituitary DI can generate the same symptoms as NDI, its cause and treatment differ. More information about the other type(s) of DI can be found at The Diabetes Insipidus Foundation, Inc..
Nine Knoers, of the University Hospital of Nijmegen in The Netherlands, defines hereditary NDI as,” a rare, inherited kidney disorder, characterized by insensitivity of the distal renal nephron to the antidiuretic effect of vasopressin. As a consequence, the kidney loses its concentrating ability and produces large volumes of hypotonic urine (50-100 mosm/kg H20), which may lead to severe dehydration and electrolyte imbalance (hypernatremia and hyperchloremia).”
Types of NDI
Inherited
There are three types of inherited NDI:
- X-linked NDI is the most common type of inherited NDI. It affects males more often than females. Males are certain to be seriously affected by NDI if they inherit the gene, whereas females are usually affected mildly or not at all. Rarely, girls may be affected as severely as boys. Females who carry this gene, whether or not they show symptoms, will pass it on to their daughters and their sons 50% of the time.
- Autosomal recessive NDI is a much rarer type of inherited NDI. It affects males and females equally. For a child to have the disease, both parents must carry this gene. Parents who are both carriers of this form of NDI have a 25% chance with each pregnancy of having another affected child.
- Autosomal dominant NDI is an extremely rare type of NDI. It affects both males and females. For a child to inherit this type of NDI, only one parent need carry the gene.
Inherited NDI is very rare. Those who inherit it may begin showing symptoms in the first few days of life.
Acquired
NDI can be acquired at any time:
- through the use of certain prescription drugs,
- as a result of a physical condition, or
- because of an underlying systemic disease or disorder.
Acquired NDI occurs more frequently than inherited NDI, but is still a rare disorder. It is usually less severe than inherited NDI and usually occurs in adults. This is because acquired NDI is generally due to a treatment or pathology that develops later in life.
Occurrences
- Ninety percent of the cases of inherited NDI are X-linked.
- One of the leading authorities in the field, Daniel G. Bichet, estimates that for every million males, four are likely to have X-linked NDI.
