body water balance and diabetes insipidus C W7

Question 1

how do disorders of excess water usually present?

Answer 1

hyponatraemia - low serum sodium concentration

Question 2

investigation of hyponatraemia - is the patient dehydrated…

Answer 2

yes - urine Na+>20mmol/l?
no - is the patient oedematous?

Question 3

investigation of hyponatraemia - is urine Na+>20mmol/l…

Answer 3

yes - renal Na+/water loss
no - non renal Na+/water loss

Question 4

investigation of hyponatraemia - is the patient oedematous…

Answer 4

yes - oedematous disorder
no - is urine osmolarity greater than twice the plasma osmolarity or greater than 500mmol/l?

Question 5

investigation of hyponatraemia - is urine osmolarity greater than twice the plasma osmolarity or greater than 500mmol/l?

Answer 5

yes - SIADH
no - non SIADH retained water excess

Question 6

types of renal Na+/water loss?

Answer 6

Addison’s
Diuretic excess
renal disease
osmotic diuresis

Question 7

types of non-renal Na+/water loss?

Answer 7

gut losses
skin
cystic fibrosis

Question 8

types of oedematous disorder?

Answer 8

cardiac failure
liver failure
nephrotic syndrome

Question 9

types of non SIADH retained water excess?

Answer 9

low GFR
ACTH/GC deficient (GC = glucocorticoid)
severe hypothyroidism

Question 10

SIADH?

Answer 10

syndrome of inappropriate anti-diuretic hormone

Question 11

causes of SIADH?

Answer 11

intracranial
intrathoracic
neoplasms
drugs

Question 12

treatment of SIADH

Answer 12

fluid restriction
may increase solute intake (acute - IV hypertonic saline)
must normalise chronic hyponatraemia slowly