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.