Kidney Stones Are On The Rise In The US And We Don't Know Why

These large kidney stones had to be surgically removed. US Air Force photo/Staff Sgt. Mareshah Haynes

Aliyah Kovner 19 Feb 2018, 11:15

Another day, another American health crisis.

Researchers from the Mayo Clinic in Minnesota have noted an extreme rise in the number of kidney stone cases over the last 30 years. If you’re fortunate enough to be unfamiliar with this medical event, here’s some background.

Kidney stones are hard chunks of accumulated mineral that form in the kidneys when the body is not properly filtering urine of crystal-forming salts. The stones can be made of calcium, oxalate, uric acid, struvite, or cystine, and range in size from tiny, grainy clusters that pass through the body undetected, to multiple pound behemoths that must be surgically removed.

Most people are familiar with stones that fall somewhere in the middle – coming in at several millimeters in diameter – because these are the ones large enough to cause an excruciating pain called renal colic as they exit the kidney and pass into the ureter on the way to the bladder, and/or as they leave the bladder and scrape their way to the outside world via the urethra.

The Mayo Clinic team was interested in both symptomatic (aka agonizing) and asymptomatic cases, and reviewed the medical records from a total of 3,224 adult “stone formers” treated between 1984 and 2012.

Their analysis, published in Mayo Clinic Proceedings, showed that the rate of symptomatic confirmed events, wherein the stone was actually seen, doubled in men and quadrupled in women. Most of the stones were made of either calcium oxalate or calcium phosphate, whereas the rates of the other types did not change significantly.

"What we're seeing is an interesting combination of things; certainly, they've gone up quite a bit both in men and women," said author Dr John Lieske to CNN.

"The absolute increase has been similar, but because women started out quite a bit lower 30 years ago, their proportion increases quite a bit more."

Medical scientists are still unsure why some people develop calcium kidney stones and others do not. A few studies have suggested that taking high dose vitamin D and calcium supplements can increase the risk of calcium oxalate kidney stones. But counterintuitively, other research has found that diets high in calcium-rich foods may actually protect against stone formation while and low calcium diets could put you at risk.

Genetics, inflammatory bowel disease, hyperactive parathyroid glands, obesity, certain medications, and undergoing a gastric bypass operation have also all been linked to calcium stones.

The common thread between all these possible causes is that they result in some sort of imbalance between levels of mineral salts and fluid in the blood or urine. 

So, if you’re hoping to avoid one the worst pain experiences known to humankind, stay on top of your hydration.

"Drinking extra water dilutes the substances in urine that lead to stones," says the Harvard Health Blog. "Strive to drink enough fluids to pass 2 liters of urine a day, which is roughly eight standard 8-ounce cups.

Fortunately for us all, especially those who cannot possibly drink that much water each day without peeing every five minutes, the increased frequency found by Dr Lieske and his colleagues is unlikely to be as quite as extreme in the country as a whole. White people are genetically predisposed to kidney stones more than people from other ethnic groups, and the Minnesota region where this study was conducted is 90 percent white. 

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