Kidney: water 3 (Disorders of urinary concentration)

Question 1

Causes of Central Diabetes Insipidus

Answer 1

Defieciency in ADH secretion, caused by lesion of:
* Hypothalamus
* Hypothalamo-hypophyseal tract
* Posterior pituitary gland

Question 2

Causes of Nephrogenic Diabetes Insipidus

Answer 2

Inability of kidney to respond to ADH, due to Congenital defect in V2 receptors of Collecting duct

Question 3

Manifestations of Diabetes insipidus

Answer 3

• Polyuria: Large amounts of diluted urine
• Polydipsia: drinking alot of water

If sense of thirst is depressed in any way (loss of conciousness), results in fatal dehydration

Question 4

Causes of Syndrome of Inappropriate ADH secretion (SIADH)

Answer 4

Excess secretion of ADH from:
* posterior pituitary gland
* malignant tumour (bronchogenic carcinoma)

Question 5

Manifestations of SIADH

Answer 5

• Excess water retention
• Hyponatremia (sodium deficiency)
• Edema (caused by water shifting to interstitial space as a result of decreased plasma osmolarity

Question 6

Explain how SIADH causes hyponatremia

Answer 6

1. Excess water retention
2. Hypervolemia
3. Reduced Renin secretion
4. Inhibition of RAAS system & reduced Angiotensin II secretion
5. Decrease Aldosterone secretion
6. Decrease Sodium reabsorption

Question 7

Treatment of SIADH

Answer 7

ADH receptor blockers

Question 8

Treatment of SIADH

Answer 8

ADH receptor blockers