Systemic paediatrics: Bartter syndrome: practice question

A Pediatrics 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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Pediatrics · Systemic paediatrics: Bartter syndrome

Sample item

A 2-year-old has polyuria, failure to thrive and normal blood pressure. Potassium is 2.6 mmol/L with metabolic alkalosis, renin and aldosterone are high, and urine calcium is raised. Which transporter is defective?

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

The answer and the reasoning

C. Na-K-2Cl cotransporter in the thick ascending limb

Bartter syndrome is a loss of function in the thick ascending limb transport system (NKCC2, ROMK or related), mimicking chronic loop diuretic use with salt wasting, hypokalaemic alkalosis, hypercalciuria and secondary hyperaldosteronism. Gitelman syndrome mimics a thiazide, with hypocalciuria and hypomagnesaemia. Treatment includes potassium, sodium and prostaglandin inhibitors.

Option by option

  • A. Thiazide-sensitive Na-Cl cotransporter in the distal tubule

    A defective thiazide-sensitive cotransporter is Gitelman syndrome, with low urinary calcium.

  • B. Aquaporin-2 water channel

    Aquaporin-2 defects cause nephrogenic diabetes insipidus without alkalosis.

  • C. Na-K-2Cl cotransporter in the thick ascending limb (correct)

    Correct. NKCC2 loss produces loop-diuretic-like effects with hypercalciuria.

  • D. Epithelial sodium channel with gain of function

    ENaC gain of function is Liddle syndrome, with hypertension and low renin.

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 Pediatrics question

What is the answer to this Pediatrics question?

The best answer is C, Na-K-2Cl cotransporter in the thick ascending limb. Bartter syndrome is a loss of function in the thick ascending limb transport system (NKCC2, ROMK or related), mimicking chronic loop diuretic use with salt wasting, hypokalaemic alkalosis, hypercalciuria and secondary hyperaldosteronism.

Why is "Thiazide-sensitive Na-Cl cotransporter in the distal tubule" not the answer?

A defective thiazide-sensitive cotransporter is Gitelman syndrome, with low urinary calcium.

Why is "Aquaporin-2 water channel" not the answer?

Aquaporin-2 defects cause nephrogenic diabetes insipidus without alkalosis.

Why is "Epithelial sodium channel with gain of function" not the answer?

ENaC gain of function is Liddle syndrome, with hypertension and low renin.

What concept does this question test?

It tests Systemic paediatrics: Bartter syndrome in Pediatrics. Gitelman syndrome mimics a thiazide, with hypocalciuria and hypomagnesaemia. Treatment includes potassium, sodium and prostaglandin inhibitors.

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 Systemic paediatrics: Bartter syndrome?

Memorise milestones and the vaccine schedule as tables and revise them often. Then use the flashcards and the other Pediatrics 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.