Kidney stones are small, hard deposits that form inside your kidneys. The stones are made of mineral and acid salts. It has many causes and can affect any part of your urinary tract — from your kidneys to your bladder. Often, stones form when the urine becomes concentrated, allowing minerals to crystallize and stick together.
Passing kidney stones can be quite painful, but the stones usually cause no permanent damage. Depending on your situation, you may need nothing more than to take medication for the pain and drink lots of water to pass a kidney stone. In other instances, surgery may be needed. Your doctor may recommend preventive treatment to reduce your risk of recurrent kidney stones if you're at increased risk of developing them again.
A kidney stone may not cause symptoms until it moves around within your kidney or passes into your ureter (the tube connecting the kidney and bladder). At that point, these signs and symptoms may occur:
- Severe pain in the side and back, below the ribs.
- Pain that spreads to the lower abdomen and groin.
- Pain that comes in waves and fluctuates in intensity.
- Pain on urination.
- Pink, red or brown urine.
- Cloudy or foul-smelling urine.
- Nausea and vomiting.
- Persistent urge to urinate.
- Urinating more often than usual.
- Fever and chills if an infection is present.
Pain caused by a kidney stone may change — for instance, shifting to a different location or increasing in intensity — as the stone moves through your urinary tract. See a doctor when you find yourself having any of the above signs and symptoms.
Seek immediate medical attention if you experience
- Pain so severe that you can't sit still.
- Pain accompanied by nausea and vomiting.
- Pain accompanied by fever and chills.
- Blood in your urine.
- Difficulty passing urine.
Kidney stones often have no definite, single cause, although several factors may increase your risk.
Kidney stones form when your urine contains more crystal-forming substances — such as calcium, oxalate and uric acid — than the fluid in your urine can dilute. At the same time, your urine may lack substances that keep crystals from sticking together, creating an ideal environment for kidney stones to form.
Types of kidney stones
Knowing the type of kidney stone helps determine the cause and may give clues on how to reduce your risk of getting more kidney stones. Types of kidney stones include:
- Calcium stones Most kidney stones are calcium stones, usually in the form of calcium oxalate. Oxalate is a naturally occurring substance found in food. Some fruits and vegetables, as well as nuts and chocolate, have high oxalate levels. Your liver also produces oxalate. Dietary factors, high doses of vitamin D, intestinal bypass surgery and several metabolic disorders can increase the concentration of calcium or oxalate in urine. Calcium stones may also occur in the form of calcium phosphate.
- Struvite stones Struvite stones form in response to an infection, such as a urinary tract infection. These stones can grow quickly and become quite large, sometimes with few symptoms or little warning.
- Uric acid stones Uric acid stones can form in people who don't drink enough fluids or who lose too much fluid, those who eat a high-protein diet, and those who have gout. Certain genetic factors also may increase your risk of uric acid stones.
- Cystine stones These stones form in people with a hereditary disorder that causes the kidneys to excrete too much of certain amino acids (cystinuria).
- Other stones Other, rarer types of kidney stones can occur.
Factors that increase your risk of developing kidney stones include:
- Family or personal history If someone in your family has kidney stones, you're more likely to develop stones, too. And if you've already had one or more kidney stones, you're at increased risk of developing another.
- Kidney stones are most common in adults age 40 and older, though kidney stones may occur at any age.
- Men are more likely to develop kidney stones, although an increasing number of women are developing kidney stones.
- Not drinking enough water each day can increase your risk of kidney stones. People who live in warm climates and those who sweat a lot may be at higher risk than others.
- Eating a diet that's high in protein sodium and sugar may increase your risk of some types of kidney stones. This is especially true with a high-sodium diet. Too much sodium in your diet increases the amount of calcium your kidneys must filter and significantly increases your risk of kidney stones.High body mass index (BMI)
- High body mass index (BMI) large waist size and weight gain have been linked to an increased risk of kidney stones.
- Gastric bypass surgery, inflammatory bowel disease or chronic diarrhea can cause changes in the digestive process that affect your absorption of calcium and water, increasing the levels of stone-forming substances in your urine.
- Diseases and conditions that may increase your risk of kidney stones include renal tubular acidosis, cystinuria, hyperparathyroidism, certain medications and some urinary tract infections.
Care and Treatment
It includes a combination of lifestyle changes and medications.
- Drink water throughout the day For people with a history of kidney stones, doctors usually recommend passing about 2.6 quarts (2.5 liters) of urine a day. Your doctor may ask that you measure your urine output to make sure that you're drinking enough water. If you live in a hot, dry climate or you exercise frequently, you may need to drink even more water to produce enough urine. If your urine is light and clear, you're likely drinking enough water.
- Eat fewer oxalate-rich foods 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 and soy products
- Choose a diet low in salt and animal protein Reduce the amount of salt you eat and choose a vegetarian source of protein, such as legumes.
- Choose a diet low in salt and animal protein 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. Ask 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.
Medications can control the amount of minerals and acid in your urine and may be helpful in people who form certain kinds of stones. The type of medication your doctor prescribes will depend on the kind of kidney stones you have. Here are some examples:
- Calcium stones To help prevent calcium stones from forming, your doctor may prescribe a thiazide diuretic or a phosphate-containing preparation.
- Uric acid stones Your doctor may prescribe allopurinol (Zyloprim, Aloprim) to reduce uric acid levels in your blood and urine and a medicine to keep your urine alkaline. In some cases, allopurinol and an alkalinizing agent may dissolve the uric acid stones.
- Uric acid stones To prevent struvite stones, your doctor may recommend strategies to keep your urine free of bacteria that cause infection. Long-term use of antibiotics in small doses may help achieve this goal. For instance, your doctor may recommend an antibiotic before and for a while after surgery to treat your kidney stones.
- Cystine stones. Cystine stones can be difficult to treat. Your doctor may recommend that you drink more fluids so that you produce a lot more urine. If that alone doesn't help, your doctor may also prescribe a medication that decreases the amount of cystine in your urine.