Chemical Pathology: General Questions

Question 1

First-line management in patients with hypercalcaemia?

Answer 1

IV 0.9% Saline

Question 2

What causes pseudo-hyponatraemia?

Answer 2

• Hyperlipidaemia
• Sample taken from drip arm

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Excess lipids and protein in the blood dilute the sample

Question 3

-What is a ‘true’ hyponatraemic state?

Answer 3

-Hyponatraemia with reduced serum osmolality

Question 4

Hyponatraemia with Hyperkalaemia and urine osmolality >20mmol/L indicates what?

Answer 4

-A renal cause of hyponatraemia (eg Chronic Kidney Disease)

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This is because kidney disease causes protein loss as protein is leaked out through the filters within the kidney that are the glomeruli. This causes a reduced circulating volume. This reduced circulating volume causes activation of the renin-angiotensin system, causing a rise in sodium levels. Rise in sodium levels cause the release of antidiuretic hormone (ADH) from the posterior pituitary leading to retention of water and hypervolaemic ‘hyponatraemia’. Water reabsorption by the ADH causes an increase in urine osmolality.

Question 5

What the fuck actually is Addison’s disease

Answer 5

-Primary adrenal insufficiency (reduced aldosterone and reduced cortisol). This causes and increase in ACTH because the pituitary is trying to get the adrenals to do their job.

Question 6

Clinical features of Addisons?

Answer 6

Hyperpigmentation

Postural Hypotension

Weight Loss

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There are more but ya know

Question 7

Hyponatraemia, Plasma osmolality <270mmol/L, Urine osmolality >100 mmol/L, High urine sodium >20 mmol/L, euvolaemia, No adrenal, renal or thyroid dysfunction. Most likely diagnosis?

Answer 7

SIADH

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Can be due to mamy things, namely carbamazepine

Question 8

In a nutshell what is Conn’s?

Answer 8

Aldosterone excess

Question 9

Ok so you’ve got a hyponatraemic patient. How would you differentiate between Diuretic use and CCF?

Answer 9

Diuretic use would show urin osmolality >20 mmol/L (Renal cause of hyponatraemia) wheras CCF would show urine osmolality <20 mmol/L (non-renal cause of hyponatraemia)

Question 10

Ok so you’ve got a hyponatraemic patient. How would you differentiate between CCF use and CKD?

Answer 10

CCF use would show urine osmolality <20 mmol/L (Non-renal cause of hyponatraemia) wheras CKD would show urine osmolality >20 mmol/L (Renal cause of hyponatraemia)

Question 11

Ok so you’ve got a hyponatraemic patient, How would you differentiate between Diarrhoea and Hyperlipidaemia?

Answer 11

Diarrhoea woudl show a reduced osmolality, whereas hyperlipidaemia would cause a pseudohyponatraemia, which would show a normal osmolality.