Acid-base biochemistry: anion gap: practice question

A Biochemistry 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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Biochemistry · Acid-base biochemistry: anion gap

Sample item

Which acid-base disorder typically produces a high anion gap metabolic acidosis?

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

The answer and the reasoning

B. Lactic acidosis from shock

Lactic acid is an unmeasured anion, so tissue hypoperfusion raises the anion gap. Diarrhoea instead causes a normal-anion-gap hyperchloremic metabolic acidosis.

Option by option

  • A. Primary hyperaldosteronism

    Hyperaldosteronism promotes metabolic alkalosis and hypokalaemia.

  • B. Lactic acidosis from shock (correct)

    Correct. Lactate raises the measured anion gap.

  • C. Chronic vomiting

    Vomiting causes loss of gastric acid and metabolic alkalosis.

  • D. Diarrhoeal bicarbonate loss

    Diarrhoea loses bicarbonate with compensatory chloride retention.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is B, Lactic acidosis from shock. Lactic acid is an unmeasured anion, so tissue hypoperfusion raises the anion gap.

Why is "Primary hyperaldosteronism" not the answer?

Hyperaldosteronism promotes metabolic alkalosis and hypokalaemia.

Why is "Chronic vomiting" not the answer?

Vomiting causes loss of gastric acid and metabolic alkalosis.

Why is "Diarrhoeal bicarbonate loss" not the answer?

Diarrhoea loses bicarbonate with compensatory chloride retention.

What concept does this question test?

It tests Acid-base biochemistry: anion gap in Biochemistry. Diarrhoea instead causes a normal-anion-gap hyperchloremic metabolic acidosis.

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 Acid-base biochemistry: anion gap?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.