Nephrology and electrolytes: uric acid stone prevention: 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: uric acid stone prevention

Sample item

A 52-year-old man with gout has recurrent renal colic. A plain abdominal radiograph shows no calcification, but ultrasound shows a stone. Urine pH is persistently 5.0 and serum urate is high. Which measure best reduces recurrence?

AAdd a thiazide diuretic to cut urinary calcium lossBLower urine pH further using oral ammonium chloride tabletsCRestrict dietary calcium as strictly as possibleDRaise urine pH to about 6.5 with potassium citrate

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

The answer and the reasoning

D. Raise urine pH to about 6.5 with potassium citrate

Uric acid stones are radiolucent and form in persistently acidic urine, because uric acid is poorly soluble at low pH. Alkalinising urine to a pH of about 6 to 6.5 with potassium citrate, along with high fluid intake, dissolves and prevents them. Allopurinol is added when urate excretion is very high.

Option by option

A. Add a thiazide diuretic to cut urinary calcium loss
Thiazides help calcium stones with hypercalciuria, not radiolucent uric acid stones.
B. Lower urine pH further using oral ammonium chloride tablets
Acidifying the urine would worsen uric acid precipitation.
C. Restrict dietary calcium as strictly as possible
Strict calcium restriction is not advised and does not address uric acid solubility.
D. Raise urine pH to about 6.5 with potassium citrate (correct)
Correct. Alkalinisation makes uric acid more soluble and can dissolve existing stones.

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, Raise urine pH to about 6.5 with potassium citrate. Uric acid stones are radiolucent and form in persistently acidic urine, because uric acid is poorly soluble at low pH.

Why is "Add a thiazide diuretic to cut urinary calcium loss" not the answer?

Thiazides help calcium stones with hypercalciuria, not radiolucent uric acid stones.

Why is "Lower urine pH further using oral ammonium chloride tablets" not the answer?

Acidifying the urine would worsen uric acid precipitation.

Why is "Restrict dietary calcium as strictly as possible" not the answer?

Strict calcium restriction is not advised and does not address uric acid solubility.

What concept does this question test?

It tests Nephrology and electrolytes: uric acid stone prevention in General Medicine. Alkalinising urine to a pH of about 6 to 6.5 with potassium citrate, along with high fluid intake, dissolves and prevents them. Allopurinol is added when urate excretion is very high.

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: uric acid stone prevention?

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.