Diabetes insipidus

Question 1

define diabetes insipidus

Answer 1

passage of large volumes of dilute urine?

Question 2

define passage of large volumes.

Answer 2

> 3 l/24 hr

Question 3

define dilute urine.

Answer 3

< 300 mosm/kg

Question 4

what are the two forms of diabetes insipidus?

describe each?

Answer 4

↓ADH secretion from posterior pituitary gland - called cranial diabetes insipidus

insensitive to ADH – called nephrogenic diabetes insipidus

Question 5

ADH normal function?

Answer 5

reabsorb water

Question 6

ADH effect on Na+ conc?

Answer 6

↓[Na+]

Question 7

ADH effect on osmolality?

Answer 7

↓osmolality

Question 8

define osmolality?

Answer 8

conc. of a solution

Question 9

Insipidus etymology?

why was it given this name then?

Answer 9

tasteless

since urine low of electrolytes has no taste.

Question 10

Causes of cranial Diabetes insipidus?

-7

Answer 10

• idiopathic
• post head injury
• pituitary surgery
• craniopharyngiomas
• histiocytosis X
• DIDMOAD is the association of cranial Diabetes Insipidus, Diabetes Mellitus, Optic Atrophy and Deafness (also known as Wolfram’s syndrome)
• Haemochromatosis

Question 11

Causes of nephrogenic DI?

-5

Answer 11

• genetic: mutations can affect the vasopressin (ADH) receptor or the aquaporin 2 channel
• electrolytes: hypercalcaemia, hypokalaemia
• lithium - lithium desensitizes the kidney’s ability to respond to ADH in the collecting ducts
• demeclocycline
• tubulo-interstitial disease: obstruction, sickle-cell, pyelonephritis

Question 12

most common form of DI?

Answer 12

central DI after head trauma or surgery

Question 13

Dehydration signs?

-2

Answer 13

dry mucosa, lose skin turgor

Question 14

urology signs on US bladder/kidney?
-2

why do these signs happen?
(same reason for both basically)

Answer 14

Hydronephrosis – lots of urine in renal pelvis

Bladder enlarged – lots of urine in it

Question 15

suspected DI.

blood tests to order?
-3

Answer 15

U + Es
ADH plasma test
Blood glucose

Question 16

suspected DI.

blood tests to order?

results for each?

Answer 16

U + Es, blood: ↑osmolality & ↑electrolytes
ADH plasma test - ↓ADH
Blood glucose - ↑

Question 17

urine osmolality and electrolyte concentration?

Answer 17

↓osmolality

↓electrolytes

Question 18

what other Ix do you do asides from blood?
(a non-invasive one that pt does at home)

result?

Answer 18

24 hr urine collection to determine urine volume - ↓

Question 19

nephrogenic diabetes insipidus Mx?

• 2
• one is drug class

Answer 19

thiazides, low salt/protein diet

Question 20

central diabetes insipidus Mx?

• 1
• drug name

Answer 20

desmopressin

Question 21

desmopressin is basically an analogue of what?

Answer 21

vasopressin

Question 22

thiazides group?

Answer 22

diuretics

Question 23

thiazides moa?

Answer 23

stops reabsorption of sodium (Na+) and chloride (Cl−) at the distal convoluted tubules i.e. put more sodium in urine

Question 24

e. g. of thiazide?

- 1 drug name

Answer 24

bendroflumethiazide