Nephrology: 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: chloride-responsive metabolic alkalosis

Sample item

A 24-year-old woman with BMI 17 kg/m2 has weakness and palpitations. She is mildly dehydrated with a normal blood pressure. Arterial pH is 7.52, HCO3 36 mmol/L, PaCO2 46 mmHg, serum K 2.8 mmol/L and urinary chloride 10 mmol/L. What is the most appropriate treatment?

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

The answer and the reasoning

B. Isotonic saline with potassium chloride replacement

Metabolic alkalosis with a low urinary chloride (below 20 mmol/L) is chloride-responsive and reflects volume contraction, as in surreptitious vomiting. Saline repletes chloride and volume, switching off the aldosterone drive that wastes potassium and hydrogen ions, and potassium chloride corrects hypokalaemia. A high urinary chloride with hypertension would suggest mineralocorticoid excess.

Option by option

  • A. Oral acetazolamide alone

    Acetazolamide would waste more potassium and would not correct the underlying volume and chloride depletion.

  • B. Isotonic saline with potassium chloride replacement (correct)

    Correct. Volume and chloride repletion corrects the alkalosis, while potassium chloride replaces the deficit.

  • C. Imaging of the adrenal glands for an aldosterone-producing adenoma

    Primary aldosteronism causes hypertension with chloride-resistant alkalosis, so adrenal imaging is not indicated.

  • D. Spironolactone

    Spironolactone treats mineralocorticoid excess with high urinary chloride and hypertension, which are absent here.

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.

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Questions about this General Medicine question

What is the answer to this General Medicine question?

The best answer is B, Isotonic saline with potassium chloride replacement. Metabolic alkalosis with a low urinary chloride (below 20 mmol/L) is chloride-responsive and reflects volume contraction, as in surreptitious vomiting.

Why is "Oral acetazolamide alone" not the answer?

Acetazolamide would waste more potassium and would not correct the underlying volume and chloride depletion.

Why is "Imaging of the adrenal glands for an aldosterone-producing adenoma" not the answer?

Primary aldosteronism causes hypertension with chloride-resistant alkalosis, so adrenal imaging is not indicated.

Why is "Spironolactone" not the answer?

Spironolactone treats mineralocorticoid excess with high urinary chloride and hypertension, which are absent here.

What concept does this question test?

It tests Nephrology: chloride-responsive metabolic alkalosis in General Medicine. Saline repletes chloride and volume, switching off the aldosterone drive that wastes potassium and hydrogen ions, and potassium chloride corrects hypokalaemia. A high urinary chloride with hypertension would suggest mineralocorticoid excess.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: 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.