- The kidneys filter out fluids and waste from the body, producing urine. The two kidneys are located deep behind the abdominal organs, below the ribs and toward the middle of the back.
- Kidney stones are hard, solid particles that form in the urinary tract. If a stone (even a small one) blocks the flow of urine, excruciating pain may result, and prompt medical treatment may be needed.
Types of Stones:
- Calcium Stones. About 70 - 90% of all kidney stones are made of calcium.
- Uric Acid Stones. Uric acid is responsible for close to 10% of kidney stones. It is the breakdown product of purines, nitrogen compounds found in our bodies and in certain foods.
- Struvite Stones. Struvite stones are almost always associated with certain urinary tract infections.
- Cystine Stones. Cystine is an amino acid, a building block of proteins. The tendency to form these stones is inherited.
- Xanthine Stones. These stones are extremely uncommon and usually occur as a result of a rare genetic disorder.
- Patients who undergo roux-en-Y gastric bypass surgery are at greater risk for kidney stones, because the procedure increases the amount of oxalate (which contributes to stone formation) and decreases the amount of citrate (which helps prevent stone formation) in the urine. Another type of obesity surgery, gastric banding, does not appear to increase the risk for kidney stones.
- Drinking citrus-based sodas (such as 7Up and Sprite) might help prevent stones from forming, particularly in patients with low citrate in their urine or those who have a tendency to form uric acid stones.
- The same diet that is recommended to control blood pressure might also reduce the risk for kidney stones. The DASH diet, which encourages the consumption of fruits and vegetables and limits animal protein, appears to reduce the incidence of kidney stones by as much as 40 - 50%.
- In about 85% of patients, the kidney stones are small enough that they pass through normal urination, usually within 2 - 3 days.
- If the stone has not passed in 2 - 3 days, the patient will need additional treatments. In some severe cases, hospitalization may be necessary.
- Alpha blockers (such as tamsulosin) can relax muscles in the urinary tract, helping kidney stones pass.
- Depending on the type of kidney stone, dietary changes, medicines, and other noninvasive treatments are available.
- A procedure to remove or break up a stone is usually needed if the stone is too large to pass on its own, if there are signs that the stone is growing, if the stone is blocking the urine flow, or if it causes a urinary tract infection or kidney damage.
- Treatments for stones are much less invasive than in the past. Major surgery is performed in less than 2% of patients.
Review Date: 06/08/2010
Reviewed By: Reviewed by: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.