• Conditions InDepth: Kidney Stones

    Kidney stones are one of the most common and painful kidney disorders. About 10% of men and 3% of women will develop a kidney stone at some point in their lives. For many, stones become a chronic problem. People who get one stone are more likely to develop others.
    The kidneys, each about the size of a fist, are located in the lower back. They are connected to the bladder by narrow tubes called ureters. The kidneys act as filters for the bloodstream. They catch needed substances and return them to circulation. They also dispose of unneeded substances in urine. Urine collects in the bladder and then passes through another narrow tube called the urethra and before exiting the body.
    Kidney stones are formed when minerals and other substances accumulate in the kidneys. They become so concentrated that they crystallize into solid particles. Under normal circumstances, urine contains chemicals that keep this from happening. This action can fail under certain conditions. If the resulting crystallized particles remain small, they can pass through the urinary system without problems. Larger stones, though, can become lodged in the kidney or further down the urinary tract.
    Kidney Stone
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    There are five main types of kidney stones:
    Calcium oxalate and calcium phosphate stones —These two types are the most common. They make up about 80% of cases. These kidney stones usually form when the concentration of calcium or other minerals in the urine becomes too high. This leads to the formation of crystals and small, hard masses over time. The exact cause of kidney stone formation is unknown in approximately 50% of cases. Possible causes include:
    • Inherited conditions that cause the kidney to retain calcium or oxalate.
    • A bowel condition that causes the body to absorb too much calcium.
    • Hypercalcemia (high blood calcium) due to cancer, infection, or overactive parathyroid glands which overwhelms the kidneys’ ability to get rid of excess calcium.
    • Hyperoxaluria (high concentration of oxalate in urine) due to intestinal disorders that cause malabsorption, such as Crohn's disease or ulcerative colitis.
    • Hypomagnesiura (low concentration of magnesium in urine) due to intestinal disorders that cause malabsorption, such as Crohn's disease or ulcerative colitis.
    • Hypocitratiuria (low concentration of citrate in urine) due to metabolic disorder.
    • Renal tubular acidosis, a kidney condition that makes the urine more acidic. Kidney stones form more easily in acidic urine.
    Struvite stones —These types of stones are composed of ammonium, magnesium, and phosphate salts. These develop as the result of a urinary tract infection. They are usually seen in women. Patients with spinal cord injuries or other problems with the bladder are at a higher risk for forming this type of stone.
    Uric acid stones —May develop in people who have gout , a condition that occurs when uric acid—a byproduct of protein metabolism—accumulates in the body. They are also seen in people having chemotherapy. Preventive measures include a purine diet and medications, such as allopurinol (Zyloprim).
    Cystine stones —Due to a rare genetic disorder that causes the kidneys to accumulate excess amounts of cystine, one of the amino acids that make up proteins.
    What are the risk factors for kidney stones?What are the symptoms of kidney stones?How are kidney stones diagnosed?What are the treatments for kidney stones?Are there screening tests for kidney stones?How can I reduce my risk of kidney stones?What questions should I ask my doctor?Where can I get more information about kidney stones?


    Coe FL, Evan A, Worcester, E. Kidney stone disease. J Clin Invest. 2005;115:2598-2608.

    Kidney stones in adults. National Kidney and Urologic Diseases Information Clearinghouse website. Available at: http://kidney.niddk.nih.gov/kudiseases/pubs/stonesadults/ . Updated June 29, 2012. Accessed November 1, 2012.

    Nephrolithiasis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed . Updated September 17, 2012. Accessed November 1, 2012.

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