Nephrology and electrolytes: chloride-responsive metabolic alkalosis: practice question

A General Medicine question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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General Medicine · Nephrology and electrolytes: chloride-responsive metabolic alkalosis

Sample item

A 58-year-old man with gastric outlet obstruction has vomited for a week. Blood pH is 7.52, bicarbonate 40 mmol/L, potassium 2.9 mmol/L, and spot urine chloride is 8 mmol/L. Which treatment is most appropriate?

AOral spironolactone for mineralocorticoid excessBOral acetazolamide as the only treatmentCIntravenous furosemide to promote diuresisDIntravenous 0.9% saline with potassium chloride

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Intravenous 0.9% saline with potassium chloride

Vomiting loses hydrochloric acid and volume, producing chloride-responsive alkalosis with a low urine chloride. Volume depletion keeps the kidney retaining bicarbonate, so replacing sodium chloride and potassium corrects the alkalosis. Treating the obstruction is also required.

Option by option

A. Oral spironolactone for mineralocorticoid excess
A low urine chloride points to volume depletion, not primary aldosteronism.
B. Oral acetazolamide as the only treatment
Acetazolamide does not replace the chloride and volume deficit and wastes more potassium.
C. Intravenous furosemide to promote diuresis
Furosemide would worsen volume depletion, hypokalaemia and alkalosis.
D. Intravenous 0.9% saline with potassium chloride (correct)
Correct. Chloride and volume repletion lets the kidney excrete bicarbonate, and potassium is replaced.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this General Medicine question

What is the answer to this General Medicine question?

The best answer is D, Intravenous 0.9% saline with potassium chloride. Vomiting loses hydrochloric acid and volume, producing chloride-responsive alkalosis with a low urine chloride.

Why is "Oral spironolactone for mineralocorticoid excess" not the answer?

A low urine chloride points to volume depletion, not primary aldosteronism.

Why is "Oral acetazolamide as the only treatment" not the answer?

Acetazolamide does not replace the chloride and volume deficit and wastes more potassium.

Why is "Intravenous furosemide to promote diuresis" not the answer?

Furosemide would worsen volume depletion, hypokalaemia and alkalosis.

What concept does this question test?

It tests Nephrology and electrolytes: chloride-responsive metabolic alkalosis in General Medicine. Volume depletion keeps the kidney retaining bicarbonate, so replacing sodium chloride and potassium corrects the alkalosis. Treating the obstruction is also required.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Nephrology and electrolytes: chloride-responsive metabolic alkalosis?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.