diabetes insipidus

Question 1

Pathoetiology of DI ?

Answer 1

decreased secretion of antidiuretic hormone (ADH) from the pituitary (cranial DI) or an insensitivity to antidiuretic hormone (nephrogenic DI)

Question 2

what is DIDMOAD

Answer 2

association of cranial Diabetes Insipidus, Diabetes Mellitus, Optic Atrophy and Deafness (also known as Wolfram’s syndrome)

Question 3

causes of cranial DI ?

Answer 3

idiopathic
pituitary surgery
craniopharyngioma

infiltrative
histiocytosis
sarcoidosis
haemochromatosis

DIDMOAD

Question 4

causes of nephrogenic DI

Answer 4

MOST COMMON GENETIC :
affects the vasopression (ADH) receptor

LITHIUM - desensitizes the kidney’s ability to respond to ADH in the collecting ducts

electrolytes
-HYPERCALCEMIA - hyperparathyroidism
-HYPOKALAEMIA

tubulo-interstitial disease: obstruction, sickle-cell, pyelonephritis

Question 5

x

Answer 5

x

Question 6

x

Answer 6

x

Question 7

x

Answer 7

x

Question 8

x

Answer 8

x

Question 9

clinical presentation of DI ?

Answer 9

history of polyuria, thirst and nocturia.

dry mucous membranes, tachycardia and mild orthostatic hypotension

Question 10

x

Answer 10

x

Question 11

x

Answer 11

x

Question 12

x

Answer 12

x

Question 13

diagnosis of DI

Answer 13

high plasma osmolality,
low urine osmolality
urine osmolality of >700 mOsm/kg excludes diabetes insipidus

water deprivation test

desmopressin test - if cranial or nephrogenic urine osmolality increases (amount of water in urine increases)

Question 14

what is seen in desmopressin test ?

Answer 14

cranial DI - with desmopressin the urine osmolality should increase

nephrogenic desmopressin - urine osmolality is unchanged

Question 15

Water deprivation test indicated for ?

Answer 15

used to determine whether the patient has diabetes insipidus as opposed to other causes of polydipsia (a condition of excessive thirst that causes an excessive intake of water)

Psychogenic polydipsia - urine osmolality increases

DI - urine osmolality remains low

Question 16

what is low irine osmolality seen in DI

Answer 16

<300

Question 17

x

Answer 17

x

Question 18

management of DI ?

Answer 18

nephrogenic DI - thiazides , Low salt and protein diet

cranial DI - desmopressin

Question 19

x

Answer 19

x

Question 20

what is psychogenic polydipsia

Answer 20

Initial plasma osmolality is high in DI.

a patient drinking excessive quantities of water leading to increased polyuria. In these patients, the primary finding is an initially low plasma osmolality. Following water deprivation, the patient’s urine becomes appropriately concentrated.

Question 21

Water deprivation test: primary polydipsia

Answer 21

urine osmolality after fluid deprivation: high

urine osmolality after desmopressin: high

Question 22

x

Answer 22

x

Question 23

x

Answer 23

x

Question 24

x

Answer 24

x

Question 25

Syndrome of inappropriate ADH (SIADH) secretion results in excess ADH, what is the plasma and urine osmolality result for this patient

Answer 25

This results in low plasma osmolality and a high urine osmolality initially,