Kidney Stone Prevention

180524358Nephrolithiasis.  That's such a descriptive word; literally nephro for kidney and lithiasis for stone formation.  Would that more terminology was so very definitive!  However, as Rick and I discuss on PodMed this week, the term doesn't begin to describe the amazing pain most people report as a result of kidney stones, formed in the kidney and then passed down into the ureters on their way to the urinary bladder. Good news then in a literature review from the American College of Physicians, published in Annals of Internal Medicine, suggesting a range of dietary choices, supplements and medications to avoid forming kidney stones once you've done so in the past.

Here's what the paper states as the magnitude of the problem, "The lifetime prevalence of nephrolithiasis is 13% for men and 7% for women, with a 5-year recurrence rate after an initial event of 35% to 50% without treatment. Stones are caused by an interaction between genetics and environmental exposure." That's a whole lot of painful events it would be great to avoid.  How can we do that?

One strategy that seems to offer benefit is increasing fluid intake to the degree that at least 2 liters of urine are produced daily. Beverages to be avoided in achieving this goal are sodas acidified with phosphoric acid, usually of the cola variety. Rick advises that such information is readily available on the labeling of the product, and that some sodas use citric acid instead, which doesn't confer risk.

Evidence on diet was a bit scattered as several different types of diets were studied. Most seemed to suggest that some dietary evaluation and advice regarding diet composition was of benefit in reducing stone recurrence, and that analysis of the stone composition was necessary in providing dietary advice.

What about medications?  Thiazide diuretics, citrate therapy, and allopurinol may all provide benefit depending on the stone composition, and combination therapies may be attempted but evidence isn't abundant for additional benefit in stone formation reduction.The paper suggests that drug monotherapy be attempted after increased fluid intake fails to reduce stone formation or in people in whom increased fluid is contraindicated. And while the stone composition seems to give an indication of strategies to employ to reduce stone formation, the paper does not recommend that course as the evidence is insufficient, and also stops short of recommending blood chemistry or urine chemistry as informative.

How about the increasing number of people who are found to have existing stones incidentally?  While not addressed specifically in this paper, Rick muses that the strategies identified here may help keep stones from growing bigger or may even reverse them, so they're well worth trying when stones are found.  As I reveal on the podcast, both Rick and I have had this experience in the past, so no cola drinks for us!

Other topics this week include a vaccine for Dengue in NEJM, the import of nonobstructive coronary artery disease on heart attack and death in JAMA, and bleeding with dabigatran in JAMA Internal Medicine.  Until next week, y'all live well.

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