Medically reviewed by Susan Kerrigan, MD and Marianne Madsen
Additions/comments by Urologist Steven N. Gange, MD
Kidney stones send almost three million Americans to the doctor each year and lead to 500,000 trips to emergency rooms. Between 5% and 10% of all active stone passers may require hospitalization. Although kidney stones do form in women, they are about twice as common in men. Statistics suggest that more than one out of every eight American men will develop a kidney stone at some time during his life The highest risk occurs between the ages of 20 and 50, with a peak at age 30.
What are kidney stones made of?
About 80% of the time, the main mineral in a kidney stone is calcium, usually in combination with oxalate, but sometimes paired with phosphate or other substances. Less often, kidney stones are composed of uric acid (5% to 10%) or struvite (5% to 15%); in rare cases, they contain other chemicals such as cysteine or even certain medications.
Symptoms and Diagnosis
The terrible pain associated with kidney stones is called “renal colic” and is caused by obstruction of the flow of urine; pressure builds up behind the obstruction, causing painful swelling of sensitive structures. Although it can persist for agonizing hours, renal colic usually ends as abruptly as it begins. Relief comes when the stone moves from a narrow part of the urinary tract into a wider region, such as the bladder, where it no longer blocks urine flow. Blood in the urine and obstructed urine flow are other possible symptoms.
If your doctor suspects that you have a kidney stone, you may have diagnostic tests and procedures, such as blood testing. Blood tests may reveal too much calcium or uric acid in your blood. Blood test results help monitor the health of your kidneys and may lead your doctor to check for other medical conditions. Your doctor may also request urine testing. This test may show that you are excreting too many stone-forming minerals or too few stone-preventing substances. Another diagnostic is imaging tests, which may show kidney stones in your urinary tract. A CT scan may reveal even tiny stones. Ultrasound–a noninvasive test that is quick and easy to perform–is another imaging option to diagnose kidney stones. You may also be asked to urinate through a strainer to catch stones that you pass. Lab analysis will reveal the makeup of your kidney stones. Your doctor uses this information to determine what’s causing your kidney stones and to form a plan to prevent more kidney stones.
Treatment for kidney stones varies, depending on the type of stone and the cause. Most small kidney stones won’t require invasive treatment. Drinking enough water (1.8 to 3.6 liters) a day will keep your urine diluted and may prevent stones from forming. This may also help to pass small stones. Pain relievers such as ibuprofen (Advil, Motrin IB) or naproxen sodium (Aleve) may be recommended to relieve mild pain.
For stones that do not pass on their own, your doctor may give you a medication to help pass your kidney stone. This type of medication (known as an alpha blocker) relaxes the muscles in your ureter, helping you pass the kidney stone more quickly and with less pain.
Large stones and those that cause symptoms
Kidney stones that are too large to pass on their own or cause bleeding, kidney damage, or ongoing urinary tract infections may require more extensive treatment. Procedures may include using sound waves to break up stones. For certain kidney stones, depending on their size and location, your doctor may recommend a procedure called extracorporeal shock wave lithotripsy (ESWL). ESWL uses sound waves to create strong vibrations (shock waves) that break the stones into tiny pieces that can be passed in your urine. The procedure lasts about 45 to 60 minutes and can cause moderate pain, so you may be under sedation or light anesthesia to make you comfortable. ESWL can cause blood in the urine, bruising on the back or abdomen, bleeding around the kidney and other adjacent organs, and discomfort as the stone fragments pass through the urinary tract.
Surgery may also be indicated to remove very large stones in the kidney. A procedure called percutaneous nephrolithotomy involves surgically removing a kidney stone using small telescopes and instruments inserted through a small incision in your back. Your doctor may recommend this surgery if ESWL has been unsuccessful.
Using a scope to remove stones.
To remove a smaller stone in your ureter or kidney, your doctor may pass a thin lighted tube (ureteroscope) equipped with a camera through your urethra and bladder to your ureter.
Once the stone is located, special tools can snare the stone or break it into pieces that will pass in your urine. Your doctor may then place a small tube (stent) in the ureter to relieve swelling and promote healing. You may need general or local anesthesia during this procedure.
Prevention of kidney stones may include a combination of lifestyle changes and medications.
Drinking water throughout the day may reduce your risk of kidney stones. For people with a history of kidney stones, doctors usually recommend drinking enough fluids to pass about 2.1 quarts (2 liters) of urine a day. Your doctor may ask that you measure your urine output to make sure that you’re drinking enough water.
In addition, if you tend to form calcium oxalate stones, your doctor may recommend restricting foods rich in oxalates. These include rhubarb, beets, okra, spinach, swiss chard, sweet potatoes, nuts, tea, chocolate, black pepper, and soy products.
It is also recommended to choose a diet low in salt and animal protein. Reduce the amount of salt you eat and choose non-animal protein sources, such as legumes. Consider using a salt substitute, such as Mrs. Dash.
Continue eating calcium-rich foods, but use caution with calcium supplements. Calcium in food doesn’t have an effect on your risk of kidney stones. Continue eating calcium-rich foods unless your doctor advises otherwise. It is important to consult with your doctor before taking calcium supplements, as these have been linked to increased risk of kidney stones. You may reduce the risk by taking supplements with meals. Diets low in calcium can increase kidney stone formation in some people.
While it is important to discuss treatment and prevention options with a urologist, good hydration is essential in preventing the development of kidney stones. A risk factor for all stones, regardless of type, is dehydration. Anyone who is prone to kidney stones should pay attention to good hydration. A randomized trial has shown that drinking 2 liters of fluid a day reduces the likelihood of stone recurrence by about half.
- What causes kidney stones (and what to do) – Harvard Health Blog
- Kidney Stones | NIDDK
- Kidney Stones: Treatment and Prevention – American Family Physician
- Kidney stones: Common, painful, preventable – Harvard Health
- Kidney Stones | Kidney Stone Symptoms | Nephrolithiasis
- Kidney stones – Diagnosis and treatment
- Kidney Stone Treatment: Shock Wave Lithotripsy
- Preventive fluid and dietary therapy for urolithiasis: An appraisal of strength, controversies and lacunae of current literature