Nephrogenic Diabetes Insipidus: Type, Symptoms, Diagnosis and Treatment

Introduction

The term nephrogenic diabetes insipidus appeared in the medical literature for the first time in 1947. This condition was previously known as diabetes insipidus renalis. Nephrogenic diabetes insipidus is distinct from central diabetes insipidus, a rare disorder characterized by the body's inability to produce vasopressin. Scientists are unsure how common nephrogenic diabetes insipidus is, but they believe it is uncommon. Diabetes insipidus is classified into four types:

• Central Diabetes Insipidus: It is brought on by damage to the pituitary gland or hypothalamus. Due to the damage, the body cannot normally produce, store, or release antidiuretic hormone (ADH).

• Nephrogenic Diabetes Insipidus: It impairs the kidneys' ability to respond to ADH.

• Dipsogenic Diabetes Insipidus: It is also known as primary polydipsia, and occurs when the hypothalamus' thirst mechanism fails. As a result, it causes one to become excessively thirsty and drink an excessive amount of fluids.

• Gestational Diabetes Insipidus: It is a condition that occurs only during pregnancy.

What Is Nephrogenic Diabetes Insipidus?

Nephrogenic diabetes insipidus (NDI) is a medical condition in which the kidneys cannot balance bodily fluids properly. The body does not properly respond to antidiuretic hormone (ADH, also called vasopressin). As a result, it excretes an excessive amount of urine, which can result in rapid, sometimes dangerous dehydration. It can be inherited or acquired. NDI is caused by complete or partial arginine vasopressin resistance in the kidneys. Vasopressin is an antidiuretic hormone that the kidney uses to maintain body water balance. NDI causes excessive urine production (polyuria), chronic excessive thirst (polydipsia), and potentially severe dehydration. Repeated bouts of severe dehydration can occur if left untreated, leading to serious complications.

What Causes Nephrogenic Diabetes Insipidus?

The kidneys filter blood to eliminate waste and excess fluid from the body in the form of urine. ADH (vasopressin) is a hormone that aids the body in maintaining a healthy balance of fluid intake and urine output. ADH assists the body in determining when to produce less urine in a healthy person. When a person sweats excessively or does not drink enough fluids, higher levels of vasopressin causes the kidneys to produce less urine. When a person's body has enough fluid, lower levels of ADH signal the kidneys to produce urine.

However, if the body does not know how to respond to vasopressin properly, the kidneys produce an excessive amount of urine. This is seen in patients with nephrogenic diabetes insipidus. Nephrogenic diabetes insipidus can be inherited or acquired.

• Inherited NDI

The most common inherited nephrogenic diabetes insipidus is an X-linked trait that affects the arginine vasopressin (AVP) receptor 2 gene and has variable penetrance in heterozygous females. Females who are heterozygous for the gene may have no symptoms or a variable degree of polyuria and polydipsia, or they could be as severely affected as males. Nephrogenic diabetes insipidus is caused in rare cases by an autosomal recessive or autosomal dominant mutation in the aquaporin-2 gene, which can affect both males and females.

• Acquired NDI

Acquired nephrogenic diabetes insipidus occurs when disorders (majorly tubulointerstitial diseases) or medications disrupt the medulla or distal nephrons and hinder urine concentrating ability, causing the kidneys to appear vasopressin insensitive. Among these disorders are the following:

• Autosomal dominant polycystic kidney disease.

• Sickle cell nephropathy.

• Nephronophthisis and medullary cystic kidney disease complex.

• Release of obstructing periureteral fibrosis.

• Bardet-Biedl syndrome.

• Medullary sponge kidney.

• Hypercalcemia.

• Amyloidosis.

• Sjögren syndrome.

• Pyelonephritis.

• Certain types of cancer (e.g., myeloma, sarcoma).

Many medications, particularly Lithium, but others (for example, Demeclocycline, Amphotericin B, Dexamethasone, Dopamine, Ifosfamide, Ofloxacin, Orlistat) may cause chronic hypokalemic nephropathy. Idiopathic-acquired NDI is also possible. Any patient who is elderly, sick, or has acute or chronic renal insufficiency can develop a mild form of acquired NDI.

Furthermore, certain clinical syndromes may resemble NDI:

• During the second half of pregnancy, the placenta can secrete vasopressinase (a syndrome called gestational diabetes insipidus).

• Some patients, after pituitary surgery, secrete an ineffective ADH precursor rather than vasopressin.

What Are the Signs and Symptoms of Nephrogenic Diabetes Insipidus?

The following symptoms are common in people with nephrogenic diabetes insipidus:

• Dehydration symptoms include dry mouth, fatigue, and dizziness.

• Extreme thirst.

• Urine output in large quantities (more than three liters a day in adults and two liters daily in children).

Signs of nephrogenic diabetes insipidus in an infant may include:

• Diarrhea.

• Inability to thrive or gain weight.

• Fever.

• Irritability.

• Poor appetite.

• Seizures.

• Vomiting.

How Is Nephrogenic Diabetes Insipidus Diagnosed?

The healthcare provider can diagnose nephrogenic diabetes insipidus based on the following criteria:

• Blood tests.

• Symptoms.

• Urine tests.

• Water deprivation test, in which no liquid is consumed for several hours and urine output is measured.

• A magnetic resonance imaging (MRI) scan of the pituitary gland will be performed to look for abnormalities.

• If there is a family history of diabetes insipidus, one should consider genetic testing.

How Is Nephrogenic Diabetes Insipidus Treated?

The treatment of NDI is tailored to the specific symptoms that each person exhibits. The primary goal of therapy is to increase fluid intake while decreasing urine output. Dietary changes and drug administration are examples of specific treatments.

• Individuals suffering from NDI must drink plenty of water to avoid dehydration. Water may be required regularly for infants. If the child is unable to consume enough water to match their urine output, a feeding tube may be inserted into the stomach or intestine. Heavy sleepers may need to be roused in the middle of the night to drink water and urinate.

• To reduce urine output, dietary changes and drug therapy are used. As sodium contributes to water loss, people with NDI may be put on a very low sodium diet (0.5 grams per day).

• Diuretics (drugs that reduce the amount of water excreted in the urine) may also be used. Diuretics, such as Hydrochlorothiazide or Chlorothiazide, reduce water loss by inhibiting the amount of salt absorbed by the kidneys. These medications can be taken alone or in combination with other medications, such as Indomethacin or Amiloride. Indomethacin is a nonsteroidal anti-inflammatory drug (NSAID) that can increase urine concentration while decreasing urine output. Indomethacin, which can be used alone, has been linked to negative side effects such as gastrointestinal bleeding.

• Amiloride is a diuretic that aids in the maintenance of potassium levels, which may fall during Hydrochlorothiazide therapy.

• Individuals with acquired NDI can reverse their kidney's resistance to vasopressin by treating the underlying cause (correcting metabolic imbalances or discontinuing the drug use). This reversal, however, could take weeks. In some cases, such as those caused by the use of Lithium, it can take years for the kidneys to respond to vasopressin again, or the damage may be irreversible.

• Individuals with NDI who are scheduled for surgery and need no food or drink for a period of time before the surgery should consult the doctors. Before or during surgery, affected individuals will require proper hydration, usually through an IV.

• Genetic counseling is recommended for people with inherited forms of the disorder and their families. Other forms of treatment are symptomatic and supportive.

Conclusion

Nephrogenic diabetes insipidus is a condition that affects urine output. When the body does not properly respond to the antidiuretic hormone (vasopressin), it produces an excessive amount of urine. This can result in rapid dehydration. It can be managed by based on the symptoms through medications or dietary changes. A healthcare provider must be consulted if an individual suspects the condition.