Kidney stones can be a painful and dangerous experience. The exact causes of kidney stones in humans are not known. However, a number of factors have been found to significantly contribute to kidney stone formation. Understanding these causes can help those at risk for kidney stones prevent this medically serious condition.
Excess Calcium Absorption
The majority of kidney stones start out as calcium deposits in the kidneys or urinary tract. When calcium levels in the kidneys increase, calcium deposits can form in the kidneys or urinary tract. As these deposits grow, they can eventually break free from the kidneys and travel through the urinary tract as solid kidney stones. The National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC) explains that excess calcium in the kidneys and urinary tract is often caused by a genetic condition--hypercalciuria--which leads to increased calcium absorption and too much calcium in the urine. Hypercalciuria is estimated to be responsible for more than 50 percent of all kidney stone cases.
Acidic Urine
As you may remember from chemistry class, calcium precipitates from water in acidic conditions. In a similar fashion, calcium precipitates from fluid in the urinary tract when urine becomes acidic. Such precipitated calcium accumulates and forms the basis for solid calcium-type kidney stones. Another class of kidney stone known as a uric acid stone can similarly form when the urine acidifies. The Mayo Clinic and NKUDIC explain that genetic and lifestyle factors can increase urine acidity. It is recommended that individuals at risk for kidney stones avoid protein-rich foods as these foods can increase urine acidity. Acidic urine can also result from lack of hydration. Those at risk for kidney stones should drink at least 12 glasses of water per day to help reduce urine acidity.
Diabetes and Obesity
The "New York Times" Health Guide explains that insulin resistance also increases urine acidity and can lead to kidney stone formation. As diabetics and obese individuals often suffer from insulin resistance, they typically have overly acidic urine and are at a higher risk for developing kidney stones.
Oxalate
Oxalate is a chemical found in many leafy green vegetables. When ingested, oxalate can combine with calcium in the intestines or urinary tract to form calcium oxalate, a primary component of kidney stones. NKUDIC recommends that individuals at risk for kidney stones avoid oxalate-rich foods, such as spinach, chard, beets, chocolate and certain teas.
References
- National Kidney and Urologic Diseases Information Clearinghouse: What I Need to Know About Kidney Stones
- National Kidney and Urologic Diseases Information Clearinghouse: Kidney Stones in Adults
- National Kidney and Urologic Diseases Information Clearinghouse: Diet for Kidney Stone Prevention
- Mayo Clinic: Kidney Stones Causes
- "New York Times": Kidney Stones Causes
