Kidney stones are common. Some types run in families. They often occur in premature infants.
There are different types of kidney stones. The exact cause depends on the type of stone.
Stones can form when urine contains too much of certain substances. These substances can create small crystals that become stones. The stones take weeks or months to form.
Calcium stones are most common. They are more common in men between age 20 - 30. Calcium can combine with other substances, such as oxalate (the most common substance), phosphate, or carbonate, to form the stone. Oxalate is present in certain foods such as spinach. It's also found in vitamin C supplements. Diseases of the small intestine increase your risk of these stones.
Cystine stones can form in people who have cystinuria. This disorder runs in families and affects both men and women.
Struvite stones are mostly found in women who have a urinary tract infection. These stones can grow very large and can block the kidney, ureter, or bladder.
Uric acid stones are more common in men than in women. They can occur with gout or chemotherapy.
Other substances also can form stones, including the medications, acyclovir, indinavir, and triamterene.
The biggest risk factor for kidney stones is not drinking enough fluids. Kidney stones are more likely to occur if you make less than 1 liter of urine a day. That's slightly more than a quart.
You may not have symptoms until the stones move down the tubes (ureters) through which urine empties into your bladder. When this happens, the stones can block the flow of urine out of the kidneys.
The main symptom is severe pain that starts suddenly and may go away suddenly:
Pain may be felt in the belly area or side of the back
The stone is blocking urine flow and causing an infection or kidney damage
The pain cannot be controlled
Today, most treatments are much less invasive than in the past.
Extracorporeal shock-wave lithotripsy is used to remove stones slightly smaller than a half an inch that are located near the kidney or ureter. It uses sound or shock waves to break up stones. Then, the stones leave the body in the urine.
Percutaneous nephrolithotomy is used for large stones in or near the kidney, or when the kidneys or surrounding areas are incorrectly formed. The stone is removed with tube (endoscope) that is inserted into the kidney through a small surgical cut.
Ureteroscopy may be used for stones in the lower urinary tract.
Rarely, open surgery (nephrolithotomy) may be needed if other methods do not work or are not possible.
Call your health care provider if you have symptoms of a kidney stone.
Also call if symptoms return, urination becomes painful, urine output decreases, or other new symptoms develop.
If you have a history of stones, drink plenty of fluids (6 - 8 glasses of water per day) to produce enough urine. Depending on the type of stone, you might need medications or diet changes to prevent the stones from coming back.
Finkelstein VA. Strategies for preventing calcium oxalate stones. CMAJ. 2006;174:1407-1409.
Pietrow PK, Preminger GM. Evaluation and medical management of urinary lithiasis. In: Wein AJ, ed. Campbell-Walsh Urology. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 43.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Scott Miller, MD, Urologist in private practice in Atlanta, Georgia. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.