Diabetes Insipidus

Question 1

What is diabetes insipidus?

Answer 1

Diabetes insipidus is a condition characterised by excessive thirst and the excretion of large volumes of dilute urine due to impaired water reabsorption in the kidneys.

Question 2

What are the main types of diabetes insipidus?

Answer 2

Central diabetes insipidus (caused by deficient ADH secretion) and nephrogenic diabetes insipidus (caused by kidney resistance to ADH).

Question 3

What are the common symptoms of diabetes insipidus?

Answer 3

Polyuria, polydipsia, nocturia, and dehydration symptoms like dry mouth or fatigue.

Question 4

What causes central diabetes insipidus?

Answer 4

It is caused by damage to the hypothalamus or pituitary gland due to trauma, tumours, infections, or autoimmune conditions.

Question 5

What causes nephrogenic diabetes insipidus?

Answer 5

It results from kidney resistance to ADH, often caused by genetic mutations, chronic kidney disease, or medications like lithium.

Question 6

What is the pathophysiology of central diabetes insipidus?

Answer 6

A deficiency in ADH production leads to reduced water reabsorption in the kidneys, causing excessive water loss and dilute urine.

Question 7

What is the pathophysiology of nephrogenic diabetes insipidus?

Answer 7

The kidneys fail to respond to ADH, impairing water reabsorption and resulting in excessive urine output and dilute urine.

Question 8

How common is diabetes insipidus?

Answer 8

It is a rare condition, with central diabetes insipidus being more common than nephrogenic diabetes insipidus.

Question 9

What are the risk factors for diabetes insipidus?

Answer 9

Head trauma, pituitary surgery, genetic predisposition, chronic kidney disease, and certain medications (e.g., lithium).

Question 10

What clinical examination findings might suggest diabetes insipidus?

Answer 10

Signs of dehydration (e.g., dry mucous membranes, reduced skin turgor), hypotension, and tachycardia.

Question 11

What investigations are used to diagnose diabetes insipidus?

Answer 11

Serum osmolality, urine osmolality, plasma sodium levels, water deprivation test, and response to desmopressin.

Question 12

What does the water deprivation test assess?

Answer 12

It evaluates the kidneys’ ability to concentrate urine in the absence of water and differentiates between central and nephrogenic diabetes insipidus.

Question 13

What is the typical serum osmolality in diabetes insipidus?

Answer 13

High serum osmolality due to water loss and dehydration.

Question 14

What is the typical urine osmolality in diabetes insipidus?

Answer 14

Low urine osmolality due to the excretion of dilute urine.

Question 15

What is the role of desmopressin in the diagnosis of diabetes insipidus?

Answer 15

Desmopressin, a synthetic ADH, helps differentiate central diabetes insipidus (improved urine concentration) from nephrogenic diabetes insipidus (no improvement).

Question 16

What are the main differential diagnoses for diabetes insipidus?

Answer 16

Primary polydipsia, osmotic diuresis (e.g., diabetes mellitus), and chronic kidney disease.

Question 17

How is central diabetes insipidus managed?

Answer 17

It is treated with desmopressin (ADH replacement) and addressing the underlying cause if identified.

Question 18

How is nephrogenic diabetes insipidus managed?

Answer 18

Management includes correcting underlying causes, discontinuing causative medications, and using diuretics (e.g., thiazides) and NSAIDs to reduce urine output.

Question 19

What lifestyle advice is given to patients with diabetes insipidus?

Answer 19

Patients should maintain adequate hydration and avoid dehydration triggers like excessive heat or strenuous exercise.

Question 20

What is the role of thiazide diuretics in nephrogenic diabetes insipidus?

Answer 20

Thiazide diuretics reduce urine output by causing mild dehydration, which increases water reabsorption in the proximal tubules.

Question 21

What are the complications of untreated diabetes insipidus?

Answer 21

Severe dehydration, hypernatraemia, and potentially hypovolaemic shock.

Question 22

How does diabetes insipidus differ from diabetes mellitus?

Answer 22

Diabetes insipidus involves impaired water reabsorption leading to dilute urine, while diabetes mellitus involves high blood glucose and osmotic diuresis.

Question 23

What is the genetic cause of nephrogenic diabetes insipidus?

Answer 23

Mutations in the AVPR2 gene, affecting ADH receptor function in the kidneys.

Question 24

What medications can cause nephrogenic diabetes insipidus?

Answer 24

Lithium, demeclocycline, and certain antiviral drugs like foscarnet.

Question 25

How can diabetes insipidus be prevented?

Answer 25

Prevention involves managing underlying conditions, avoiding causative medications, and regular monitoring in at-risk patients.