SIADH and Diabetes Insipidus

Question 1

Presentation of SIADH

Answer 1

-Headache
-Fatigue
-Muscle aches and cramps
-Confusion
-Severe= seizures and reduced consciousness

Question 2

Investigation of SIADH

Answer 2

-Euvolemic
-Hyponatremia
-Low serum osmolality
-High urine sodium
-High urine osmolality

-Malignancy (small cell lung cancer)
-Stroke
-Haemorrhage
-Infection (TB, pneumonia)
-Drugs (SSRI, Sulphonylureas, carbamazepine):
=CXR, CT thorax, abdomen, pelvis, and head.

Question 3

Management of SIADH

Answer 3

-Fluid restriction
-Vasopressin receptor antagonists (tolvaptan).
-Slow correction to avoid precipitating central pontine myelinolysis.
-Demeclocycline (reduces the responsiveness of the collecting tubule cells to ADH).

Question 4

Causes of hyponatraemia

Answer 4

-Primary polydipsia (water deprivation test)
-Hypovolaemia hyponatraemia
-Hypervolaemic hyponatraemia (heart failure, liver failure and nephrotic syndrome)
-Diuretic induced hyponatraemia
-Advanced renal impairment
-Cerebral salt wasting

Question 5

Presentation of central diabetes insipidus

Answer 5

-Polyuria
-Polydipsia
-Dehydration
-Postural hypotension

-Previous head injury
-Pituitary surgery
-Craniopharyngioma
-Sarcoidosis
-DIDMOAD

Question 6

Investigation of cranial diabetes insipidus

Answer 6

-High plasma osmolality
-Low urine osmolality (>700 excludes DI)

-Water deprivation test= low after deprivation.

-High urine osmolality after desmopressin.
-Decreased ADH.
-More than 3 litres on 24hr urine collection.

Question 7

Management of cranial diabetes insipidus

Answer 7

-Desmopressin
-Risk of hyponatraemia

Question 8

Presentation of nephrogenic diabetes insipidus

Answer 8

-Polyuria
-Polydipsia
-Dehydration
-Postural hypotension

-Genetic
-Hypercalcaemia, hypokalemia
-Lithium
-Tubule-interstitial disease

Question 9

Investigation of nephrogenic diabetes insipidus

Answer 9

-High plasma osmolality
-Low urine osmolality (>700 excludes DI)

-Water deprivation test= low after deprivation, if high primary polydipsia

-Low urine osmolality after desmopressin.
-Decreased response to ADH.
-More than 3 litres on 24hr urine collection.

Question 10

Management of nephrogenic diabetes insipidus

Answer 10

-Thiazide diuretics
-Low salt/ protein diet
-High dose desmopressin
-NSAIDs