Kidney stones are one of the most painful and, unfortunately, one of the most common disorders of the urinary tract. In 2000, kidney stones accounted for 2.7 million visits to health care providers and more than 600,000 visits to emergency rooms. Fortunately, most kidney stones pass out of the body without any intervention, and research has led to a better understanding of the many factors that promote stone formation.

The kidneys are two bean-shaped organs located below the ribs toward the middle of the back. They remove extra water and wastes from the blood through urine formation. The kidneys perform a number of important body functions such as maintaining a stable balance of salts and other substances in the blood and producing hormones.

A kidney stone is a hard mass developed from crystals that separate from the urine and build up on the inner surfaces of the kidney. Normally chemicals present in urine keep crystals from forming. But these chemical inhibitors do not always work. Most crystals are so small they are passed in urine without even being noticed. However, some get large enough to cause symptoms. The most common symptom is extreme pain which occurs when a large stone moves in the kidney and blocks the flow of urine. Typically, a person feels a sharp, cramping pain in the back and side near the kidney or in the lower abdomen. Sometimes nausea and vomiting occur. If the stone grows or moves, blood may appear in the urine. As the stone moves closer to the bladder, the need to urinate may increase in frequency and may be accompanied by a burning pain. Fever and chills may indicate an infection is present and requires immediate attention by a doctor.

The causes of kidney stone formation are not well understood. While certain foods may increase the likelihood of stone formation in people who are susceptible, no foods are specifically linked to kidney stone formation. Family history, urinary tract infections, certain kidney diseases, and certain metabolic disorders are also associated with kidney stone formation. Excess calcium in the urine is inherited and is the cause of more than half of all kidney stones. High levels of calcium in the urine cause crystal of calcium oxalate or calcium phosphate to form in the urine. Another common cause of kidney stones is high levels of uric acid in the urine. Excess uric acid in the urine can result from gout, excess intake of vitamin D, urinary tract infections and blockages. Calcium oxalate stones can also form in people with chronic inflammation of the bowel or people who have had intestinal bypass surgery (ostomy surgery).

Most kidney stones are treated by drinking enough fluids to pass the stone in the urine. This is usually 2 to 3 quarts of water per day. If you have formed one kidney stone it is more likely that you will form others. Blood and urine tests may be done to determine the chemical nature of the stones formed. Drinking enough water to produce 2 quarts of urine every 24 hours is one of the best preventative measures. Supplements and antacids containing calcium may be eliminated. There is disagreement whether eliminating dairy and other calcium-containing foods prevents or worsens kidney stone formation. People who form calcium oxalate stones may be advised to limit foods that contain oxalates including spinach, coffee, tea and chocolate.

Reference: http://kidney.niddk.nih.gov/kudiseases/pubs/stonesadults/.

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