Kidney Stones

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How common are kidney stones?

Each year, more than half a million people go to emergency rooms for kidney stone problems. It is estimated that one in ten people will have a kidney stone at some time in their lives.
The prevalence of kidney stones in the United States increased from 3.8% in the late 1970s to 8.8% in the late 2000s. The prevalence of kidney stones was 10% during 2013–2014. The risk of kidney stones is about 11% in men and 9% in women. Other diseases such as high blood pressure, diabetes, and obesity may increase the risk for kidney stones.

What is a kidney stone?

A kidney stone is a hard object that is made from chemicals in the urine. There are four types of kidney stones: calcium oxalate, uric acid, struvite, and cystine. A kidney stone may be treated with shockwave lithotripsy, uteroscopy, percutaneous nephrolithomy or nephrolithotripsy. Common symptoms include severe pain in lower back, blood in your urine, nausea, vomiting, fever and chills, or urine that smells bad or looks cloudy.

Urine has various wastes dissolved in it. When there is too much waste in too little liquid, crystals begin to form. The crystals attract other elements and join together to form a solid that will get larger unless it is passed out of the body with the urine. Usually, these chemicals are eliminated in the urine by the body's master chemist: the kidney. In most people, having enough liquid washes them out or other chemicals in urine stop a stone from forming. The stone-forming chemicals are calcium, oxalate, urate, cystine, xanthine, and phosphate.

After it is formed, the stone may stay in the kidney or travel down the urinary tract into the ureter. Sometimes, tiny stones move out of the body in the urine without causing too much pain. But stones that don't move may cause a back-up of urine in the kidney, ureter, the bladder, or the urethra. This is what causes the pain.

Here's how kidneys perform their important work:

Blood enters the kidneys through an artery from the heart
Blood is cleaned by passing through millions of tiny blood filters
Waste material passes through the ureter and is stored in the bladder as urine
Newly cleaned blood returns to the bloodstream by way of veins
Bladder becomes full and urine passes out of the body through the urethra.

The kidneys perform their life-sustaining job of filtering and returning to the bloodstream about 200 quarts of fluid every 24 hours. Approximately two quarts are eliminated from the body in the form of urine, while the remainder, about 198 quarts, is retained in the body. The urine we excrete has been stored in the bladder for approximately one to eight hours.