A 62y.o male arteriopath has a sodium of 132, mild tachycardia and reduced urine output. He has recently been treated for fluid overload and had normal sodium prior to this treatment. No other relevant signs are noted. Rank the following diagnoses given this information, putting the MOST LIKELY diagnosis first, and the least likely diagnosis last:

A) Cardiac failure

B) Diabetes insipidus

C) Adrenal insufficiency

D) Diuretics

Answer - DACB

Diuretics - This person is most likely to have hyponatraemia caused by excessive treatment of their fluid overload, also making them hypovolaemic now.

Cardiac failure – This could explain the previous fluid overload in an arteriopath, but is less likely to explain the current hyponatraemia due to the fact that it did not appear until treatment began for fluid overload.

Adrenal insufficiency – This can cause hyponatraemia but would be expected to leave the patient euvolaemic and may also give additional examination findings.

Diabetes Insipidus – This causes hypernatraemia so does not explain the hyponatraemia at all.