What are Kidney Stones?
Kidney stones are clumps of minerals and salts that form in your kidneys. When there are excessive amounts of minerals and salts, your body can’t clear them and they stick together (crystallize) to become a stone. They can range in size from a grain of sand to a golf ball.
Kidney stones are formed in your kidneys but can irritate or become lodged in any part of the urinary tract. Some never leave the kidney or cause any problems. Others travel out of the kidney, through the ureter (the tube that drains urine out of the kidney), and into the bladder. When kidney stones become stuck in the ureter, blocking the flow of urine, they can become very painful.
Kidney stones may be referred to as renal calculi, uroliths, or nephroliths. The condition of having kidney stones is nephrolithiasis and the condition of having bladder stones is called urolithiasis.
What do The Kidneys do?
Your kidneys play a critical role in your urinary tract as well as the entire body. Kidneys are fist-sized filters that clean waste and toxins out of the blood. They are vital in maintaining the correct amount of water in the body.
Kidneys ensure there is an optimum electrolyte balance, which is essential for your muscles, nerves, and other body tissues to function normally.
Finally, your kidneys produce hormones that help make red blood cells, control blood pressure, and support bone health.
What are Kidney Stones Made of?
Kidney stones are made of different materials and come in many sizes and colors. Knowing the type of stone is important for proper treatment. Kidney stones are most often made of calcium.
Calcium stones account for about 80% of kidney stones. They can be made of calcium oxalate or calcium phosphate. Having calcium stones doesn’t necessarily mean you have too much calcium in your urine. They can form for other reasons as well.
Uric acid stones
Certain chemical changes in the body create uric acid as a waste product. These stones form when uric acid doesn’t dissolve well in acidic urine. Acidic urine can be caused by:
- A diet high in protein and low in fruits and vegetables
- Being overweight
- Chronic diarrhea
- Type 2 diabetes
Struvite stones result from chronic urinary tract infections (UTI). They tend to be large, fast-growing, and form branches. Chronic UTIs are often caused by kidney or bladder problems like incomplete bladder emptying. People with neurologic disorders like multiple sclerosis, paralysis, and spina bifida have the highest risk of developing struvite stones.
Cystine stones are rare and are typically caused by an inherited metabolic disorder called cystinuria. People with cystinuria have too much of an amino acid called cystine in their urine.
Kidney stones don’t always cause symptoms, and many people never even know they have them. Some kidney stones work their way out of the kidney into the ureter, which drains urine from the kidney to the bladder. If the stone travels to the bladder, it may be urinated out. In rare cases, it can become stuck in the bladder, where it can cause an infection or other complications.
It’s more common for a kidney stone to become stuck in the ureter or urethra, the tube that drains urine from your bladder out of your body. When a stone becomes stuck in the ureter or urethra, it can cause complications like infection and be very painful.
Kidney stones don’t always cause symptoms, but when they do they can include:
- Pain that:
- Feels sharp and crampy
- Is located in the back and side (called flank pain)
- May move lower in the abdomen or to the groin
- Starts suddenly
- Comes in waves
- Comes and goes
- An urgent need to urinate
- Frequent urination
- Burning during urination
- Reddish or dark urine due to blood
- Nausea and vomiting
- (Men) pain at the tip of the penis
Causes of Kidney Stones
There are many possible causes of your kidney stones. Your doctor will work with you to determine your cause. Some causes are:
Low Urine Volume
Chronic low urine volume is a significant risk factor for developing kidney stones. When urine volume is consistently low, the urine is more concentrated and doesn’t have enough fluid to dissolve excess salts and minerals. You can tell when your urine is concentrated by its color. Dark-colored urine is concentrated and is a sign that you need to drink more water. Healthy, hydrated urine is pale yellow.
If you have a history of kidney stones, you may need to drink as many as 12 glasses of water every day. Talk to your doctor about how much you should drink.
Your diet can also contribute to the formation of kidney stones. Calcium oxalate stones form when calcium in your urine combines with oxalate, a natural compound found in plants. If you’ve had a history of calcium oxalate stones, you may need to avoid high-oxalate foods like spinach, almonds, potatoes, beets, and dates.
You may also need to lower your salt intake. High calcium levels are sometimes caused by how the calcium in your body interacts with the salt and not by eating too much calcium. In that case, reducing salt intake allows your body to properly handle calcium.
Animal protein can also contribute to kidney stone formation. A diet high in proteins like beef, chicken, fish, and pork may raise acid levels, which makes it easier for stones to form.
Conditions like Crohn’s disease and ulcerative colitis can cause frequent diarrhea, leading to dehydration and low urine volume. They may also cause you to absorb too much oxalate, contributing to calcium oxalate stones.
Obesity can affect acid levels in urine and make it easier for calcium oxalate and uric acid stones to form.
Other Medical Conditions
Medical conditions that affect acid buildup or calcium metabolism can also lead to kidney stones.
Certain medications and supplements may contribute to the formation of kidney stones. Talk to your doctor about your medications and supplements and whether they may cause the formation of kidney stones.
Your risk of developing kidney stones is higher if your family members have a history of stones.
Kidney stones are often first diagnosed when blood in the urine or the pain of passing a stone leads the patient to seek medical care. Others that don’t cause symptoms are found incidentally in unrelated X-rays. Stones that don’t cause symptoms are called “silent.” When a stone is suspected, an ultrasound or CT scan can provide answers.
Treatment for kidney stones may vary from person to person or even with each stone. The type of stone, along with the intensity and length of time you’ve had symptoms, may determine the proper treatment.
- Wait For the Stone to Pass – Waiting for the stone to pass may be an acceptable option for smaller stones with mild symptoms, as long as there is no sign of infection or a blockage and you continue to drink water to help it pass. Over-the-counter pain medicine can relieve the discomfort. It could take weeks to pass a stone.
- Medication – A medication called tamsulosin (Flomax) can help by relaxing the ureter to help the stone pass. Pain and anti-nausea medications may also be needed.
If a stone won’t pass, the pain is too severe, or it’s affecting kidney function, minimally invasive treatments or surgery may be an option. Sometimes people have stones removed before they can cause symptoms.
Shock wave lithotripsy
Shockwave lithotripsy (SWL) uses shock waves to break stones into smaller pieces that are easier to pass. Ultrasound or X-rays are used to locate the stone and focus the shock waves. It works best on certain types and sizes of stones.
SWL typically requires some form of anesthesia and a few days of recovery. It may take several weeks for the pieces to pass. Although the procedure is safe, it’s possible for larger pieces to become stuck in the ureter while passing, requiring additional procedures to remove them.
A ureteroscope is a small tube with a camera and small tools on the end. Your doctor can advance the scope up into the bladder, through the ureter, and into the kidney if needed. The small camera allows your doctor to see the stone, and the tools can break it into smaller pieces or grab it for removal.
Once the stones are removed, your doctor may insert a stent to hold the ureter open to help drain the kidney. Patients can typically resume their normal activities in a few days. Stents need to be removed in four to ten days.
Percutaneous nephrolithotomy (PCNL)
PCNL is a procedure done under general anesthesia, requiring one or two weeks for recovery. It requires a small incision in the side or back just large enough to insert a nephoscope into the kidney. A tool can then be passed through the scope to break the stone into smaller pieces that can be suctioned out. A tube may be inserted for a few days to drain urine and any bleeding.
Diagnosing Why You Get Stones
Knowing what type of kidney stones you form is essential for preventing future stones. There are a number of diagnostic tools your doctor may use to narrow down your stone type.
Medical And Diet History
Your health and medical history can provide valuable clues about your kidney stones. Your doctor may ask you about your and your family’s history with kidney stones, your eating habits, and any medical conditions that may contribute, like diabetes, gout, or frequent diarrhea.
If your diet is high in foods that contribute to kidney stones or low in foods that help prevent them, your doctor can give you information about dietary changes that can help prevent future stones.
Blood And Urine Tests
As part of a physical exam, your doctor may ask for blood and urine samples to help determine if a medical condition contributes to your kidney stones. Urine can be tested for the presence of a urinary tract infection or crystals that identify stone types.
A 24-hour urine collection can give important information about the substances in your urine that form stones. The results can help determine the best diet and medications to prevent stones from forming in the future.
X-rays and CT scans may be used to look for stones.
Your doctor may ask you to urinate through a sieve to catch stones as you pass them. Stones can be sent to a lab for analysis, and the results can help your doctor choose how to help you prevent future stones.
After determining your stone type and why you’re forming them, your doctor can talk to you about how to prevent future stones. Medications and diet changes may be recommended.
Fluids – You may need to increase your fluid intake to help dissolve salts and minerals and flush them out of your body. You may need to drink as much as 100 ounces daily, taking care to avoid sugary drinks and alcohol. It may help to keep a log of everything you drink as well as all exercise. Exercise and hot weather can cause you to lose water with sweat, so you’ll need to drink even more.
Ask your doctor how much you should be drinking and urinating each day.
Salt – A diet high in sodium can cause calcium or cystine to build up. Following the Centers for Disease Control (CDC) guidelines for sodium intake – less than 2300 mg per day – can reduce your chances of developing kidney stones. It’s also healthier for your heart. Foods high in sodium that could push you over that goal include:
- Bottled salad dressings and certain condiments
- Bread and other baked goods
- Canned soups, vegetables, and sauces
- Cured meats, deli meat, sausages, and hot dogs
- Mixed-ingredient foods like pizza and pasta dishes
- Most frozen foods
- Pickles and olives
- Snacks known for being salty, like chips and crackers
- Some breakfast cereals
- Table salt and many types of spice blends
Calcium – Talk to your doctor about how much calcium you should get every day and if you’re getting the right amount from your food. Too much calcium could contribute to stones. Too little can affect your bones, heart health, and other body systems.
Some calcium-rich foods include:
- Beans, lentils
- Calcium-fortified non-dairy milk
- Fortified juices
- Winter squash
Fruits and vegetables
Fruits and vegetables are healthy sources of antioxidants, fiber, magnesium, potassium, citrate, and phytate, which may help prevent the development of stones. Five servings per day is recommended. A serving size is one piece of fruit, ½ cup of cooked vegetables, or 1 cup of raw vegetables.
If you have high levels of urine oxalate, you may need to eat more calcium-rich foods and less high-oxalate foods. Most plants have oxalate, but some have high amounts, like almonds and spinach. If you have high oxalate, talk to your doctor about what causes it and how to adjust your diet to prevent kidney stones.
Eat less meat
Eating less meat is healthier for your entire body. But it’s especially true if you make calcium oxalate or cystine stones and have high uric acid. If so, you may need to cut back on fish, lamb, pork, poultry, red meat, seafood, and wild game.
Talk to your doctor about your uric acid level, how your diet affects it, and what changes you can make to avoid forming stones.
If diet changes and fluid intake don’t prevent you from forming stones, you may be prescribed medications to help.
- Thiazide diuretics – If you have calcium stones and high urinary calcium, thiazine diuretics can help lower your urine calcium.
- Potassium citrate – Potassium citrate helps prevent kidney stones by making urine less acidic. It may be prescribed for calcium stones and low citrate in the urine.
- Allopurinol – Allopurinol is regularly prescribed to treat gout, which is a result of too much uric acid in the blood.
- Acetohydroxamic acid (AHA) – AHA can help if you produce struvite or infection stones. AHA makes urine a poor environment for struvite stones.
- Cystine-binding thiol drugs – If you make cystine stones and other treatments haven’t helped, cystine-binding thiol drugs might.
- Vitamin supplements – Talk to your doctor before taking any vitamin supplements. Some may contribute to your kidney stones.
I have kidney stones. Does that mean my children will, too?
They are more likely to develop kidney stones because a family member does. The cause may be genetic or a product of a similar lifestyle and diet.
Is surgery inevitable if my stone doesn’t pass?
You may need surgery if the stone doesn’t pass, is causing severe pain, or has caused an infection.
How can I manage kidney stones along with my heart disease and other chronic health conditions?
The diet changes you make for your heart are good for preventing kidney stones, too. A healthy diet with the recommended amount of fruits and vegetables, whole grains, low-fat dairy, and less animal protein benefits your entire body.