Pathophysiology of Water Handling

Question 1

What causes Nephrogenic Diabetes Insipidus?

Answer 1

ADH resistance

Question 2

What are the 3 main categories of hyponatremia?

Answer 2

1. hypertonic
2. isotonic
3. hypotonic

Question 2

What causes euvolemia?

Answer 2

• SIADH
• 1° Polydipsia
• Hypothyroidism
• Adrenal Insufficiency

Question 3

What causes Isotonic Hyponatremia?

Answer 3

• hyperlipidemia
• hyperproteinemia (multiple myeloma)
• ***this is a lab artifact

Question 3

What is SIADH?

Answer 3

syndrome of inappropriate ADH secretion; hypoosmolality and less than maximally dilute urine

Question 4

What causes inappropriate ADH secretion?

Answer 4

• Hypothyroidism
• drugs (nicotine, isoproterenol, SSRIs, morphine, barbs, aspirin)
• adrenal insufficiency
• 1a polydispsia

Question 4

How do you test for central diabetes insipidus?

Answer 4

kidneys should respond to exogenous AVP with a rise in Uosm of 100 mOsm/kg above the levels achieved following water deprivation

Question 4

Sodium is transported on the Na+-K+-2Cl- cotransporter in the ______ and by the thiazide-sensitive NaCl cotransporter in the ______.

Answer 4

thick ascending limb; distal convoluted tubule

Question 5

High serum uric acid levels suggest volume ______.

Answer 5

depletion

Question 6

If the UNa is less than 20 in hypervolemia, the cause is ______.

Answer 6

• CHF
• cirrhosis
• nephrotic syndromes

Question 7

_____ occur with severe or acute hyponatremia.

Answer 7

Seizures

Question 8

Low serum uric acid levels suggest ______.

Answer 8

euvolemia

Question 9

What is the equation for Serum osmolality (Sosm)?

Answer 9

2 X [Na] + [BUN/2.8] + [Glucose/18]

Question 9

For each increase in serum glucose of ____mg/dL, serum sodium will fall by about ____mEq/L.

Answer 9

100; 1.6

Question 12

______ is transported on the Na+-K+-2Cl- cotransporter in the thick ascending limb and by the thiazide-sensitive NaCl cotransporter in the distal convoluted tubule.

Answer 12

Sodium

Question 13

If the UNa is less than 20 in hypovolemia, the cause is ______.

Answer 13

extrarenal losses

Question 14

What causes Central Diabetes Insipidus?

Answer 14

ADH deficiency

Question 15

What is the tx for minor hyponatremia?

Answer 15

• dietary water restriction
• Na/Cl +/- furosemide

Question 16

What are the 3 categories of SIADH?

Answer 16

1. CA
2. pulmonary disease
3. CNS disorders

Question 17

Drugs such as ______ antagonize the end-organ effect of AVP.

Answer 17

lithium or demeclocycline

Question 18

Water deficits should be restored slowly in order to avoid ______.

Answer 18

sudden shifts in brain cell water

Question 19

What is Congenital nephrogenic DI?

Answer 19

a rare sex-linked (male) disorder in which cyclic AMP is not generated in response to AVP

Question 20

What causes decreased total body Na?

Answer 20

• GI loss (diarrhea)
• skin loss (burns)
• diuretic use without sufficient water intake
• mechanical ventilation

Question 22

What is the normal serum osmolality range?

Answer 22

280-295 mOsm/kg

Question 23

Hypernatremia occurs only when (1) ______ or (2)\_\_\_\_\_.

Answer 23

1. ADH is decreased 2. ineffective daily water intake (less than that required to compensate for normal insensible, gastrointestinal, and renal losses)

Question 25

Sodium is transported on the ______ in the thick ascending limb and by the thiazide-sensitive _____ in the distal convoluted tubule.

Answer 25

Na+-K+-2Cl- cotransporter; NaCl cotransporter

Question 26

Low serum _____ levels suggest euvolemia.

Answer 26

uric acid

Question 27

For each increase in serum _____ of 100 mg/dL, serum _____ will fall by about 1.6mEq/L.

Answer 27

glucose; sodium

Question 28

If the UNa is greater than 20 in hypervolemia, the cause is \_\_\_\_\_\_.

Answer 28

* ARF * CKD

Question 29

If the UNa is greater than 20 in hypovolemia, the cause is \_\_\_\_\_\_.

Answer 29

renal losses

Question 30

Drugs such as lithium or demeclocycline antagonize the end-organ effect of \_\_\_\_\_.

Answer 30

AVP

Question 31

What 2nd messenger does ADH use?

Answer 31

adenylate cyclase (which generates cyclic AMP)

Question 31

High serum ____ levels suggest volume depletion.

Answer 31

uric acid

Question 32

Hyponatremia is most commonly caused by \_\_\_\_\_.

Answer 32

a relative excess of water

Question 33

What causes Hypotonic Hyponatremia?

Answer 33

the nonosmotic release of ADH that prevents maximal urinary dilution --\> need to check the volume status next

Question 35

What causes Hypertonic Hyponatremia?

Answer 35

* hyperglycemia * mannitol or glycerol administration

Question 37

What causes increased total body Na?

Answer 37

hypertonic fluid administration

Question 38

\_\_\_\_\_\_ is a rare sex-linked (male) disorder in which cyclic AMP is not generated in response to AVP.

Answer 38

Congenital nephrogenic DI