Diabetes Insipidus

Question 1

How Diabetes insipidus (DI) manifests clinically ..?

Answer 1

polyuria and polydipsia and

can result from either vasopressin deficiency (central DI) or vasopressin insensitivity at the level of the kidney (nephrogenic DI [NDI])

Question 2

Extracellular fluid tonicity is regulated almost exclusively by ..?

Answer 2

by water intake and excretion

Question 3

Extracellular volume is regulated by …?

Answer 3

sodium intake and excretion

Question 4

Volume homeostasis is largely regulated by ……?

Answer 4

the renin-angiotensin-aldosterone system, with

contributions from both vasopressin and

the natriuretic peptide family

Question 5

Actions of vasopressin …?

Answer 5

anti diuretic and vascular pressor activity

Question 6

The half-life of vasopressin in the circulation is..?

Answer 6

5 min

Question 7

What is pathologic polyuria or polydipsia …?

Answer 7

exceeding 2 L/m2/24 hr

Question 8

The diagnosis of DI is established if ..?

Answer 8

The serum osmolality is >300 mOsm/kg, and

The urine osmolality is <300 mOsm/kg.

Question 9

When to do water deprivation test …?

Answer 9

If the patient’s serum osmolality is <300 mOsm/kg (but >270 mOsm/kg) and pathologic polyuria and polydipsia are present

Question 10

Inference of water deprivation test …?

Answer 10

A water deprivation test is indicated to establish the diagnosis of DI and to differentiate central from nephrogenic causes.

Question 11

Wolfram syndrome include ..?

Answer 11

DI, diabetes mellitus, optic atrophy, and deafness

Question 12

The most common primary brain tumors associated with DI ..?

Answer 12

Germinomas and pinealomas

Question 13

When to suspect germinoma ..?

Answer 13

Quantitative measurement of α-fetoprotein and β-human chorionic gonadotropin, often secreted by germinomas, should be performed in children with idiopathic or unexplained DI, in addition to serial MRI scans

Question 14

Most common common types of infiltrative disorders causing central DI. ..?

Answer 14

Langerhans cell histiocytosis

lymphocytic hypophysitis

Question 15

About etiology of Nephrogenic Diabetes Insipidus ..

…?

Answer 15

NDI can result from genetic or acquired causes.

Genetic causes are less common but more severe than acquired forms of NDI

Question 16

Genetic NDI ..?

Answer 16

Congenital X-linked NDI results from inactivating mutations of the vasopressin V2 receptor, AVPR2.

Congenital autosomal recessive NDI results from defects in the aquaporin-2 gene, AQP2.

An autosomal dominant form of NDI is associated with processing mutations of the aquaporin-2 gene.

Question 17

Acquired NDI etiology ..?

Answer 17

Hypercalcemia or hypokalemia and is associated with lithium, demeclocycline, foscarnet, clozapine, amphotericin, methicillin, and rifampin

Question 18

What type of food to consume in DI …?

Answer 18

Patients with both central and NDI should ingest a diet without excessive solute (e.g., sodium chloride) to help decrease urine output when vasopressin action wanes.

Question 19

Treatment of central DI in older children is best accomplished with …?

Answer 19

DDAVP (desmopressin)

Question 20

Why nasal desmopressin is contraindicated in childhood enuresis …?

Answer 20

The use of DDAVP nasal spray for childhood enuresis is no longer approved due to its risk of causing hyponatremia

Question 21

TREATMENT For Congenital NDI ..?

Answer 21

T he main goals are to ensure the intake of adequate calories for growth and to avoid severe dehydration.

Foods with the highest ratio of caloric content to osmotic load (Na <1 mmol/kg/24 hr) should be ingested to maximize growth and to minimize the urine volume required to excrete the solute load

Question 22

Rationale of thiazides in acquired NDI …?

Answer 22

Thiazides appear to induce a state of mild volume depletion by enhancing sodium excretion at the expense of water and by causing a decrease in the glomerular filtration rate, which results in proximal tubular sodium and water reabsorption