Renal and acid–base: urine chloride in metabolic alkalosis: practice question

A Physiology 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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Physiology · Renal and acid–base: urine chloride in metabolic alkalosis

Sample item

A 25-year-old woman has normal blood pressure, a serum potassium of 2.8 mmol/L and metabolic alkalosis. A urine diuretic screen is negative, and urinary chloride is very low. Which cause is most likely?

APrimary hyperaldosteronismBCurrent loop diuretic useCSurreptitious vomitingDBartter syndrome

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

The answer and the reasoning

C. Surreptitious vomiting

In vomiting, loss of gastric chloride and volume depletion drive renal chloride conservation, so urinary chloride is very low and the alkalosis is chloride-responsive. In primary hyperaldosteronism, Bartter syndrome and current diuretic use, the kidney wastes chloride and the urinary chloride is high.

Option by option

A. Primary hyperaldosteronism
Primary hyperaldosteronism causes hypertension and a high urinary chloride.
B. Current loop diuretic use
Current loop diuretic use gives high urinary chloride and would show on the screen.
C. Surreptitious vomiting (correct)
Correct. Chloride and volume depletion lead to renal chloride retention and low urinary chloride.
D. Bartter syndrome
Bartter syndrome causes renal chloride wasting, with high urinary chloride.

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 Physiology question

What is the answer to this Physiology question?

The best answer is C, Surreptitious vomiting. In vomiting, loss of gastric chloride and volume depletion drive renal chloride conservation, so urinary chloride is very low and the alkalosis is chloride-responsive.

Why is "Primary hyperaldosteronism" not the answer?

Primary hyperaldosteronism causes hypertension and a high urinary chloride.

Why is "Current loop diuretic use" not the answer?

Current loop diuretic use gives high urinary chloride and would show on the screen.

Why is "Bartter syndrome" not the answer?

Bartter syndrome causes renal chloride wasting, with high urinary chloride.

What concept does this question test?

It tests Renal and acid–base: urine chloride in metabolic alkalosis in Physiology. In primary hyperaldosteronism, Bartter syndrome and current diuretic use, the kidney wastes chloride and the urinary chloride is high.

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 Renal and acid–base: urine chloride in metabolic alkalosis?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.