PrepTest 114, Section 2, Question 2
One way kidney stones can form is when(46 more words not shown)
Which one of the following,(11 more words not shown)
- ALaboratory studies on(19 more words not shown)
- BIncreasing dietary oxalate(13 more words not shown)
- CKidney stone development(18 more words not shown)
- DIncreasing calcium intake(19 more words not shown)
- ESome kidney stones(13 more words not shown)
Reading the argument
Eating more calcium doesn't automatically mean more calcium reaches the kidneys. That is the connection I want to examine. The passage identifies an excessive concentration in urine as one way stones form. It doesn't yet tell us exactly how dietary calcium affects that concentration. Could an inherited condition matter? Could the way the body processes calcium matter? Those are questions, not extra medical facts we can supply.
Then we get the surprising result: for many people, increasing calcium intake lowers the chance of another stone. We need to explain that decrease. Simply saying diet isn't the only influence wouldn't be enough.
What we’re looking for
My first guesses are that the higher-calcium diet might accompany another helpful change, or that it might contain less oxalate. Perhaps one of those differences offsets the apparent problem. The question asks for a fact that helps resolve the discrepancy, so let's look for a connection that makes more calcium in the diet fit with fewer recurrences.
Working the answers
- A
This gives us a similar observation in animals. It could add evidence that the pattern occurs, but it doesn't explain why adding calcium would go along with fewer additional stones. Repeating the surprising result in another group leaves the central question unanswered. We are not looking for existing stones to disappear; the passage concerns the chance of new ones.
- B
This changes two parts of the situation: oxalate goes up and calcium goes down. Our puzzle concerns calcium going up and the chance of recurrence going down. B doesn't tell us why that combination occurs. Sharing the same mineral names doesn't make it an explanation of the particular result.
- C
An inherited source of excessive calcium or oxalate could help explain why dietary intake isn't the whole story. But why would increasing intake reduce recurrence? C doesn't connect that increase to the improvement. A reason diet might be less important than expected is different from a reason the observed change goes in the opposite direction.
- DCorrect
Here is a specific explanation of how the body processes the extra calcium. More calcium is eliminated through the intestines, leaving less for the kidneys to filter. So more going into the body can mean less reaching the place where the problematic concentration occurs.
This differs from my guesses about other health changes or less oxalate. It directly answers the link we questioned at the start: dietary calcium and calcium reaching the kidneys needn't rise together. D says the latter decreases. It doesn't say no calcium reaches the kidneys, and it needn't guarantee that nobody ever gets another stone.
- E
This tells us another way stones can differ in composition. It doesn't tell us what increasing calcium does to any of those stones or to the risk of recurrence. Knowing there are other kinds of stones leaves the effect of the dietary change unexplained.
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