What are kidney stones?
Kidney stones are small pieces of hard, crystallized material that form in the kidney. Kidney stones are often made up of calcium, but can also contain uric acid or amino acids (proteins). Kidney stones, also called urolithiasis, are a common condition.
One or more kidney stones can form in one or both kidneys. Kidney stones begin as tiny specks and may gradually increase in size. A person with a small kidney stone may not have symptoms and may not be aware of the condition. In some cases, small stones in the urine may pass out of the kidney and move down the ureter, into the bladder, and out of the body without causing pain or serious problems.
There are generally no symptoms of a large kidney stone that remains in the kidney. However, when a large kidney stone moves out of the kidney into the ureter toward the bladder, it causes severe flank, abdominal, and groin pain, called renal colic. Some have described renal colic as the most intensely painful experience encountered in life. Other symptoms of a large kidney stone that has moved out of the kidney include blood in the urine, difficulty urinating, and nausea, with or without vomiting.
Kidney stones may be preventable in some cases by ensuring good hydration and with prescribed medication if you are in a high-risk population, such as those with a personal history of kidney stones. Once a stone has developed and causes symptoms, treatment may include hospitalization, pain medication, and certain procedures that remove or crush large stones so that the stones can move more easily out of the body. Small kidney stones may not require treatment.
Most kidney stones pass out of the body in the urine. On occasion, a kidney stone can get stuck in a ureter and result in potentially serious, even life-threatening complications, such as kidney infection and kidney damage. Seek immediate medical care (call 911) if you, or someone you are with, have symptoms of passing a kidney stone, such as severe flank or abdominal pain, not urinating, or bloody urine. Rapid diagnosis and treatment can help reduce the risk of complications.
What are the different types of kidney stones?
Normally, the kidney has enough fluid to wash out a variety of chemicals through the urine. However, when not enough liquid is present, certain chemicals—calcium, cystine, phosphate, urate and xanthine—can form into crystals that attract other elements to become kidney stones.
The four types of kidney stones that can develop from these chemicals are:
Calcium-compound stones, including calcium oxalate and calcium phosphate. Calcium oxalate stones are the most common form of kidney stones. They are linked to eating foods high in oxalate, such as beets, black tea, bran flakes, nuts, rhubarb, and spinach.
Uric acid stones, which are more likely in men, as well as people who have gout, inflammatory bowel disease, low urine output, or a diet high in red meat and other animal proteins. They can also develop in people who have undergone chemotherapy.
Struvite stones are more common in women. They are also known as infection stones if they develop with a kidney infection or urinary tract infection (UTI). If they grow larger, struvite stones may also be called staghorn calculi.
- Cystine stones, a less common type most often found in people with a hereditary disorder, cystinuria, that causes elevated cystine in the urine
What are the symptoms of kidney stones?
Small kidney stones or kidney stones that do not move and remain in the kidney may not produce any symptoms. A small kidney stone may pass in the urine out of the body without causing pain or visible blood in the urine.
When a large kidney stone moves out of the kidney and into the ureter, it generally causes severe, sharp and stabbing pain in the flank area of the lower back. This is called renal colic. Renal colic often comes in waves of severe pain that can be accompanied by profuse sweating, restlessness, irritability, nausea and vomiting.
As a kidney stone moves down the ureter toward the bladder, the pain can move from the flank area to the lower abdominal area and into the groin. Pain may also radiate into the testicles or the labia. If the kidney stone passes into the bladder, the pain usually resolves. Once in the bladder, a kidney stone generally is able to move easily out of the bladder, into the urethra, and out of the body during urination.
Symptoms that might indicate a serious condition
Kidney stones can be extremely painful and lead to serious complications, such as kidney infection and kidney damage. Seek immediate medical care (call 911) if you, or someone you are with, have any symptoms of passing a kidney stone including:
Bloody or pink-colored urine (hematuria)
Dark or tea-colored urine
Difficult urination or lack of urination
Nausea and vomiting
Severe flank pain that can move or radiate to the lower abdomen, groin, labia, or testicles
What causes kidney stones?
Kidney stones are tiny hard stones that form in the kidney as a result of a buildup of crystallized material. Kidney stones are often made up of calcium, but they can also contain uric acid or amino acids (proteins). One or more kidney stones can form in one or both kidneys. Kidney stones begin as tiny specks and may gradually increase in size.
What are the risk factors for kidney stones?
Several factors increase the risk of developing kidney stones. Not everyone with risk factors will develop kidney stones.
Risk factors for kidney stones include:
Dehydration, including long-term mild dehydration, which results in the production of smaller amounts of urine that contain a higher concentration of substances that form kidney stones, such as calcium and amino acids
Family history for kidney stone formation
Gout (a type of arthritis caused by a buildup of uric acid in the joints)
Intestinal malabsorption (due to conditions like Crohn’s disease or following surgery)
Male biological sex
Personal or family history of kidney stones or certain kidney defects, such as horseshoe kidney
Prolonged exposure to a hot climate or high altitudes. People living in these areas lose more body water and produce smaller amounts of urine. As a result, their urine contains a higher concentration of substances that form kidney stones.
Prolonged inactivity, such as being bedridden
- Urinary tract infection
Reducing your risk of kidney stones
Not all people who are at risk for kidney stones will develop the condition, and not all people who develop kidney stones have risk factors. You may be able to lower your risk of developing kidney stones by:
Avoiding dehydration. This means drinking plenty of water and fluids so that your urine is consistently very light or clear in color. If you exercise vigorously or live at a high altitude or in a hot, dry climate, you will need to consistently drink significantly more fluids than a person who has a moderate exercise level or lives in a more tropical climate or lower altitude.
Drinking lemonade made from real lemons, which has qualities that may prevent the formation of kidney stones
Eating a well-balanced diet that includes moderate portions of protein
Following your treatment plan for such conditions as a urinary tract infection and gout
Getting regular exercise
Maintaining a healthy weight and losing excess weight
- Taking medications as prescribed to prevent the formation of certain types of kidney stones
What are the diet and nutrition tips for preventing kidney stones?
To prevent kidney stones from forming, or from recurring if you have had them in the past, your doctor may recommend a specific diet plan. If necessary, a registered kidney dietitian can help you make changes to your diet to reduce your risk of kidney stones and improve overall kidney health.
While there is no single diet plan that can stop kidney stones, general nutrition tips for kidney stone prevention include:
Drinking plenty of water, to encourage urine production and flush out the chemicals and minerals that can develop into kidney stones. This is particularly important in the summer months or during activities in which you lose more water through sweat, which can reduce urine output.
Avoiding foods high in oxalate, the compound that helps form calcium oxalate stones, the most common type of kidney stone. Foods with naturally high levels of oxalate include beets, black tea, chocolate, nuts, potatoes, rhubarb, spinach, and Swiss chard.
- Make sure you’re getting enough calcium, which may seem counterintuitive to preventing calcium oxalate stones. In truth, a lack of calcium increases your risk of kidney stones. Doctors recommend consuming 1,000 to 2,000 mg of calcium per day. You can achieve this through three daily servings of dairy foods, such as low-fat milk, low-fat yogurt, and low-fat cheese, as well as through certain fresh fruits and vegetables like oranges, broccoli and soybeans.
Reducing sodium, which includes table salt along with many packaged foods that contain added sodium, such as canned soups, potato chips, condiments, and fast food. Excess sodium contributes to a loss of calcium, which increases your risk of kidney stones, among other conditions.
- Limiting animal protein, particularly red meat and organ meats like liver or kidney, which can raise levels of uric acid in the body and increase risk of uric acid stones (and gout). Reduce portions of other animal proteins, including eggs, dairy, and fish, in favor of plant-based proteins, such as beans, soy and lentils.
Ask your healthcare provider for guidance before making significant changes to your diet.
How do doctors diagnose kidney stones?
Doctors diagnose kidney stones based on an evaluation of the patient’s symptoms and medical history, a physical exam, and a variety of tests.
If you are experiencing symptoms of kidney stones, your doctor or licensed healthcare practitioner will ask you several questions related to your symptoms, including:
How long have you been experiencing pain?
Where is the pain located?
Is the pain radiating to other parts of your body?
Do you have a family history of kidney stones?
Do you have other health conditions, such as gout or inflammatory bowel disease?
How much water do you drink each day?
- What types of foods are in your diet?
Tests your doctor may use to diagnose kidney stones include:
Urinalysis, which evaluates a urine sample for the presence of blood or minerals that may indicate a stone
Blood test, to look for elevated levels of certain minerals that can cause kidney stones
X-ray, which in some cases can show the location of the stone and how it is affecting the urinary tract
- Computed tomography (CT), an imaging scan that may or may not use liquid contrast to highlight the location and size of the kidney stone
What are the treatments for kidney stones?
It is common for a person with a small kidney stone to not be aware of the condition. In fact, it may pass out of the body spontaneously without any treatment. Larger kidney stones that move out of the kidney often require treatment.
General treatment of kidney stones
General treatment of kidney stones includes:
Drinking fluids to dilute the urine and help flush out a kidney stone
- Pain medications, which, for large stones, may be given intravenously by emergency care providers
Surgical treatment of kidney stones
If a kidney stone does not pass out of the body with fluids and pain medications, it may have become lodged in the ureter. A variety of procedures may be considered to remove the stone. These include:
Cystoscopy, in which specialized instruments are passed into the ureter through the bladder to withdraw a kidney stone that has become lodged in the lower third of the ureter. A similar procedure may be used to remove or crush the kidney stone using a laser or ultrasonic probe.
- Extracorporeal shock wave lithotripsy, a procedure that is performed for a kidney stone located in the upper ureter or in the kidney. In this procedure, the kidney stone is pulverized by a machine using painless high-energy sound waves (also known as shock waves).
In rare cases in which kidney damage has occurred, it may be necessary to remove the affected kidney. This surgery is a nephrectomy.
What are the potential complications of kidney stones?
Complications of kidney stones can be serious and life-threatening. You can help minimize your risk of serious complications by following the treatment plan your healthcare professional designs specifically for you.
Serious complications of kidney stones include:
Adverse effects of treatment
Hydronephrosis (buildup of fluid and swelling of the kidney)
Kidney infection (pyelonephritis)
Permanent kidney damage and loss of normal kidney function
- Ureteropelvic junction obstruction (UPJ obstruction; scarring and obstruction of the ureter that blocks urine flow from the kidney)