QuestionSBA
QuestionChoice
This would result in hyponatraemia which is not seen in this patient's blood results.
10027833
c
Syndrome of inappropriate anti-diureitc hormone secretion (SIADH)
QuestionChoice
This describes a condition where the renal tubules can no longer handle acids effectively. This results in hypokalaemia, as the kidneys try to compensate for the acidosis. However, for this case, it would not explain the hypophosphataemia or hypomagnesemia.
10027834
d
Renal tubular acidosis
QuestionChoice
This would make sense with this woman's history of chemotherapy. However, it only explains the hypokalaemia, not the other electrolyte abnormalities.
10027832
b
Prolonged vomiting
QuestionChoice
The history of loss of appetite followed by sudden return to usual eating habits fits with the downregulation of enzymes in the urea cycle and then the build-up of toxic waste products once eating commences. The fact she is cachexic supports the idea that she has not been eating well for a long time and is therefore at risk of refeeding syndrome. The blood results show hypophosphatemia, hypokalaemia and hypomagnesemia which happens due to the shifting of electrolytes into the intracellular space from the extracellular spaces.
10027831
a
Refeeding syndrome
QuestionChoice
Vitamin D deficiency would explain the hypophosphataemia, but not the other electrolyte abnormalities.
10027835
e
Vitamin D deficiency
Concept
Chapter
2693
6006
Refeeding syndrome
Topic
170
Clinical Chemistry
17964
You are asked to review a 45-year-old woman who is complaining of fatigue and muscle cramping. She finished her third round of chemotherapy for metastatic breast cancer last week. She tells you that the chemotherapy made her lose her appetite completely, but since it finished she has gone back to her usual appetite. On examination, she appears very cachexic but otherwise well.
Blood results are shown below:


||||
|---------------------------|:-------:|--------------------|
|Sodium|136 mmol/L|135 - 145|
|Potassium|2.7 mmol/L|3.5 - 5.3|
|Magnesium|0.65 mmol/L|0.7 - 1.0|
|Phosphate|0.33 mmol/L|0.8 - 1.5|
|Urea|3.4 mmol/L|2.5 - 7.8|
|Creatinine|59 µmol/L|60 - 120|


What is the most likely cause of this electrolyte abnormality?
a