The kidneys are hard-working organs, filtering about 200 quarts of blood each day. The filtering process gathers about half a gallon of waste and excess water that is then passed from the body as urine. Signs of kidney failure don't begin to show up until the kidneys are working at only 20 percent of normal capacity. These include prolonged flu-like symptoms, headaches, nausea and vomiting, itching over the entire body, fatigue, swelling in the extremities, low urine output, cramps and darkened skin. Routine urine and blood tests can detect kidney problems at an earlier stage. When kidney function drops to only 10 percent of normal, end stage renal failure occurs, necessitating either dialysis or a kidney transplant. 
[SOURCE: "Kidney Failure," Mayo Clinic Health Letter, October, 2000]

Fewer Stones for the Lower Classes
                                                                                               

Kidney stones tend to occur more frequently in affluent, industrially developed countries, and some experts attribute the increased incidence of kidney stones over the past several decades to rising affluence. Persons with a large intake of meat and animal protein have a higher risk of forming stones than those consuming mostly plant products.

[SOURCE: Aisling E. Courtney and A. Peter Maxwell, “Renal Medicine: Renal Stone Recurrence Can Be Prevented,” The Practitioner, February 23, 2007]

Kidney Stone Prevention: Normal 
Calcium, Less Protein and Sodium
                                   

High concentration of calcium in the urine is a risk factor for calcium oxalate kidney stones, but scientists now believe that eating too little calcium-rich foods is not a solution since this may lead to increased absorption of oxalate. A randomized, controlled study found that a diet with a normal amount of calcium combined with reduced protein and sodium was more effective than a low-calcium diet in preventing the recurrence of stones.

[SOURCE: Yadav Rajiv and Kumar Rajeev, “Dietary Modifications for Preventing Recurrent Kidney Stones,” Indian Journal of Urology, October-December, 2006]

Kidney Stones on Rise–Why?
                                                                                               

An increasing number of kidney stones have been diagnosed in recent years, and scientists believe that at least some of this increase may be linked to an increased incidence of diabetes. In a Mayo Clinic study involving 3,561 cases of kidney stones diagnosed between 1980 and 1999, researchers found a significant association between kidney stones and a diagnosis of diabetes. Among subjects with uric acid stones, the prevalence of diabetes was 40 percent.

An earlier study based on data from the Health Professionals Follow-Up Study, the Nurses Health Study and the National Health and Nutrition Survey (NHANES II) found that weight gain and obesity increased the risk of kidney stones. “Larger body size may result in increased urinary excretion of calcium, oxalate, and uric acid, thereby increasing the risk for calcium-containing kidney stones,” wrote the author of the study.

[SOURCE: John C. Lieske, et al, American Journal of Kidney Diseases, 2006;48:897-904; Eric N. Taylor, et al, JAMA, January 26, 2005]

What You Drink Does Matter
                                                                                               

To prevent kidney stones, doctors recommend increasing urine volume by drinking plenty of fluids–two to three liters a day.
Water is always a good choice; it’s plentiful, inexpensive and zero calories per serving. Studies show that individuals who drink coffee and beer have a decreased risk of kidney stones. One study found that orange juice was better than other citrus juices such as lemonade in raising levels of citrate in the urine and reducing the formation of stones.

[SOURCE: Vadim A. Finkelstein and David S. Goldfard, “Strategies for Preventing Calcium Oxalate Stones,” Canadian Medical Association Journal, May 9, 2006; Sherri Damlo, “Orange Juice Helps Prevent the Formation of Kidney Stones, American Family Physician, December 15, 2006 from Journal of the American Society of Nephrologists, October 26, 2006]