What Are Kidney Stones?
Kidney stones are hard, pebble-like masses or crystals that can form inside your kidneys. They can result from the minerals and salts that are dissolved in your pee, especially if you haven't been drinking enough water. You might hear your doctor call them renal calculi, nephrolithiasis, or urolithiasis.
Kidney stones may be as small as a grain of salt or as big as a kernel of corn. The stones usually look brown or yellow, and they may be smooth or rough.
Kidney stones are common in adults, and the rate is rising. About one of every 11 adults in the U.S. will have a kidney stone at some point in their life. People who are assigned male at birth (AMAB) have about double the risk of developing them as people who are assigned female at birth (AFAB). People who are AMAB and in their 30s-40s are most likely to get them. They also seem to be more common in non-Hispanic white people.
Read on to learn more about the symptoms, causes, diagnosis, and treatments for kidney stones.
Kidney Stone Symptoms
You can have kidney stones and not have any symptoms. If you have kidney stones that are small enough to pass through your system without getting stuck, you may not have any symptoms. You may find out you have them only when your doctor does imaging for another problem and finds them then.
You usually won't have any symptoms unless a stone moves into one of the two tubes (called ureters) that connect your kidney and your bladde r.
What do kidney stones feel like?
The most common symptom is sharp flank pain, which is pain between your lower ribs and hip on the same side you have the stone. The pain may spread to your lower back, belly, or groin. Your doctor might refer to this symptom as renal colic. This is pain that happens when a stone has moved out of your kidneys and into your urinary tract, where it's gotten stuck. Depending on the size of the stone and where it's stuck, your pain may be mild or severe. The pain may come in waves or range in severity. It may hurt when you pee if the stone has made it further down into your urethra before getting stuck.
Other signs and symptoms of kidney stones include:
- Pee that's cloudy, foamy, pink, red, or brown
- Seeing crystals in your pee
- Feeling like you have to pee all the time or have to pee right now
- Bad-smelling pee
- A burning sensation when you pee
- Producing less urine when you do pee
- Fever and chills
- Nausea and vomiting
When to call a doctor
If you’re in really bad pain, you’ll probably want to go to the ER. Other signs you should go see your doctor include:
- Nausea and vomiting because of pain
- Fever and chills with pain
- Signs of an infection, such as having cloudy pee or blood in your pee, bad-smelling pee, or difficulty peeing
What Causes Kidney Stones?
You get kidney stones from high levels of certain minerals or salts in your pee, such as:
- Calcium
- Oxalate
- Phosphorus
- Uric acid
Kidney stones form when you don’t have enough pee in your body to keep the concentration of these minerals low in your kidneys. Or you may not have enough of certain chemicals in your pee that keep the crystals from forming clumps. Stones usually take months or years to form.
Factors that may increase your risk for kidney stones include:
Low volume of pee from dehydration. You can tell when your pee volume is too low when it's dark and concentrated. If you're well hydrated, your pee should be pale yellow.
High levels of some minerals or salts in your diet, such as:
- Sodium
- Calcium
- Protein
- Oxalate (from foods such as almonds, green leafy vegetables, potatoes, grains, soy, tea, rhubarb, and beets)
Some medical conditions, such as:
- Inflammatory bowel disease (ulcerative colitis and Crohn’s disease), as these can cause you to have chronic diarrhea that leads to dehydration
- Parathyroid disease, as it can cause high levels of calcium in your blood
- Distal renal tubular acidosis, which causes acid to build up in your body
- Inherited conditions, such as cystinuria (which causes the amino acid cysteine to build up in your pee) or primary hyperoxaluria (where your liver makes too much oxalate)
- Having surgery on your stomach or intestines, such as gastric bypass surgery
- Cystic fibrosis
- Diabetes
- High blood pressure
- Gout
- Obesity
- Kidney cysts
- Osteoporosis
- Hemiplegia or paraplegia, which are types of paralysis
- Pregnancy
A family history of kidney stones, especially in your parents or siblings.
Some medications and supplements, such as:
- Diuretic s for high blood pressure
- Antiseizure and migraine medicines
- Calcium-based antacids
- Vitamin C supplements
- Calcium supplements
Types of Kidney Stones
Doctors break down kidney stones into types depending on what they are mostly made of. Knowing which type you have is helpful because it affects your treatment and may help you figure out how to stop getting new ones.
Types of kidney stones include:
Calcium stones
About 80% of kidney stones are made of calcium. Calcium stones can be made from calcium oxalate (most common) or calcium phosphate. Anything that raises the levels of calcium or oxalate in your pee can make you more likely to get calcium stones.
Uric acid stones
About 5%-10% of kidney stones are made of uric acid, which is a waste product your body makes. You're more likely to form uric acid crystals if your pee is acidic. You may have acidic pee due to:
- Being overweight
- Having conditions such as chronic diarrhea, type 2 diabetes, or gout
- Having a diet that's both high in animal proteins and low in fruits and vegetables
Struvite/infection stones
About 10% of kidney stones are made of struvite (also called magnesium ammonium phosphate). If you get chronic urinary tract infections (UTIs), you may be at increased risk for this type of stone. This is because bacteria that can cause UTIs make the pH of your pee alkaline, which allows struvite crystals to form. These stones can grow large, with lots of branching. They may also grow very fast.
Cystine stones
This is the least common type; only about 1% of kidney stones are made of cystine. Cystine is a chemical made from two cysteine amino acids that have bonded together. This type is usually due to an inherited metabolic disorder called cystinuria, which keeps your kidneys from reabsorbing cystine from your pee. These usually start forming when you're still a child.
How Are Kidney Stones Diagnosed?
If you have symptoms of kidney stones, your doctor will start by asking about your medical history and doing a physical exam. They'll ask you:
- To describe your symptoms
- If you have any health conditions that increase your risk for kidney stones
- Whether anybody in your family has kidney stones
- What you typically eat
They may also order some tests, such as:
Blood tests
These can show if your blood has high levels of minerals that can lead to kidney stones. They can also tell your doctor about how healthy your kidneys are.
These can show if you have high levels of minerals in your pee that can cause kidney stones. They can also detect the presence of blood, white blood cells, or bacteria in your pee, which may indicate an infection.
Analysis of passed stones. As part of your urine test, your doctor may also have you pee through a strainer to catch any stones you pass. They’ll send them to a lab to find out what they’re made of. This can tell them what’s causing your stones and how to treat them.
Your doctor may refer you for a kidney, ureter, and bladder (KUB) X-ray. A KUB X-ray will give your doctor an idea about the size, shape, and position of your kidneys, ureters, and bladder, and show if there are stones in your kidneys or ureters.
Not all stones are visible on X-ray, so your doctor may also do a CT scan, which can show:
- The size and location of a stone
- Whether a stone is blocking your urinary tract
- Any conditions that may have caused your stones
During an X-ray or CT scan, your doctor may also use a contrast dye in a procedure called an intravenous pyelogram (IVP). The technician will inject a dye into one of your veins and then watch the movement of the dye through your kidneys, ureter, and bladder on imaging. For instance, if the dye doesn't move or moves too slowly, it suggests you have a block or barrier in your urinary tract.
If you're pregnant and in your first trimester, you'll probably get an ultrasound rather than an X-ray or CT scan. That's because developing babies are most at risk for a radiation injury in this early stage of pregnancy. If you are in your second or third trimesters, you may get a low-dose CT scan.
Kidney Stone Treatment
Treatment is based on the size, location, and type of kidney stones you have.
Small stones may pass through your urinary tract without needing any special treatment. About 80% pass on their own. To help you pass the stone, your doctor may suggest that you:
- Drink at least eight 8-ounce glasses of water a day.
- Take over-the-counter NSAIDs, which can help lessen your pain and inflammation. Or, your doctor may prescribe a pain medicine. Ask your doctor before taking ibuprofen because it can increase your risk for kidney failure when you have kidney stones, especially if you have underlying health conditions.
- Take a medication, such as tamsulosin (Flomax) and nifedipine (Adalat or Procardia), to relax the muscles in your ureter, the tube that carries urine from your kidneys to your bladder. This helps you pass the stone more quickly and with less pain.
If your stone is bigger or you can’t pass it, you may be in a lot of pain. You may also be vomiting, which can dehydrate you. In this case, you need to go to the ER to get IV fluids and antinausea medicine.
The amount of time it takes to pass your stone will vary depending on how big and where it is. For instance, stones smaller than 4 millimeters (about 1/8 of an inch) around may pass in about 1-2 weeks. Once it gets to your bladder, it generally passes in a few days. Stones larger than 4 millimeters around may take 2-3 weeks to pass.
If you can't pass the stone on your own, your doctor can break up the stone into smaller pieces in a few different ways. These are usually outpatient procedures, which means you won't need general anesthesia or an overnight stay in the hospital. These procedures include:
Shock wave lithotripsy (SWL)
This is the most common procedure to remove kidney stones in the U.S. It uses shock waves, which can blast the stone into little pieces, which you can pass more easily when you pee.
Cystoscopy and ureteroscopy
Your doctor will use a thin, flexible scope (cystoscope or ureteroscope) to look inside your urethra and bladder to see and remove or break apart any stones you have in your urethra, bladder, ureters, and kidneys.
If the above methods don't help, you may need to have surgery to remove them, usually using a minimally invasive technique. Unlike SWL, cystoscopy, and ureteroscopy, these must be done in the hospital with anesthesia, and you may need to stay in the hospital for a couple of days. For instance, you may need:
A form of laparoscopic surgery called percutaneous nephrolithotomy
It's rare, but if you have large stones, you may need surgery. Your surgeon cuts a small slit in your back and inserts a tool called a nephroscope into your kidney to find any stones. Depending on the size of your stones, they may use an ultrasound probe to break apart the stones before removal.
For more complex cases, you may need to have your stones removed through a larger incision in your back.
How to Prevent Kidney Stones
Once you get a kidney stone, you’re at higher risk of getting more in the future. It helps to know what caused your previous stone. Your doctor or a dietitian can make suggestions for ways to change your diet to help prevent future kidney stones.
Here are some strategies your doctor may recommend:
Drink plenty of water
This is one of the best ways to prevent most types of kidney stones. This is because staying hydrated keeps your pee dilute enough to prevent mineral crystals from forming.
Doctors usually recommend you drink at least eight 8-ounce glasses of water each day. You may need more or less depending on your size, the weather, your activity level, and your medical history. For instance, if you've had cystine stones, you may need to drink more than eight 8-ounce glasses. If you have kidney failure, urinary incontinence, or urinary frequency and can't drink that much water, ask your doctor for recommendations. When you're well-hydrated, your pee is a clear, pale yellow, so use that to guide how much water you drink.
Some of this liquid can be replaced with citrus drinks, such as orange juice or lemonade. Some studies seem to show that the citrate in citrus drinks can help protect you from getting kidney stones. Citrate seems to stop mineral crystals from forming stones.
Cut back on certain foods, such as:
- Sodium and salty foods. This can help prevent calcium stones. Lots of sodium can raise calcium levels in your urine, which increases your risk for kidney stones.
- Oxalate. This can also help prevent calcium oxalate stones. Common foods high in oxalate include nuts, peanuts, rhubarb, spinach, and wheat bran.
- Animal protein. This can help prevent calcium and uric acid stones.
- Sugary foods. In particular, foods with table sugar and high fructose corn syrup can increase the levels of oxalate in your pee.
Get enough calcium
This preventive step might sound a little confusing, as doctors will tell you that high calcium levels (because of too much sodium) in your urine can cause a stone. Not getting enough calcium can raise oxalate levels in your urine. It’s best to get your calcium from foods and beverages rather than supplements because they can make you more likely to get kidney stones.
Kidney stone diet
Your doctor may recommend you follow the Dietary Approaches to Stop Hypertension (DASH) diet, which may help prevent kidney stones. In general, the DASH diet recommends you focus on vegetables, fruits, and whole grains. You can add some fat-free or low-fat dairy products, fish, poultry, beans, nuts, and vegetable oils. Only eat limited amounts of saturated fat, fatty meat, full-fat dairy products, tropical oils (coconut, palm kernel, and palm), sweets, and sugar-sweetened drinks.
Preventive medications
If you've had kidney stones, your doctor may prescribe a medicine to help prevent future ones. The treatment will depend on the type of stones you had:
- For calcium stones, you may get potassium citrate tablets to prevent mineral crystals from forming stones and to keep your pee a bit acidic. You may also get diuretics to keep the pee moving through your kidneys.
- For uric acid stones, you may get potassium citrate and allopurinol, which lowers your uric acid levels.
- For struvite stones, you may get antibiotics, including acetohydroxamic acid, which is often used to prevent infections.
- For cystine stones, you may get potassium citrate and mercaptopropionyl glycine, which is a heart medicine that can also help keep cystine stones from forming.
Kidney Stone Complications
Kidney stones may put you at risk for certain conditions, such as:
- Hydronephrosis, a condition where a blockage makes pee back up into your kidney, causing it to swell
- Pyelonephritis, which is a kidney infection
- Acute kidney injury, a reversible type of kidney failure
- Frequent UTIs
- Chronic kidney disease (CKD)
Takeaways
Kidney stones are hard masses that can form inside your kidneys. They form from the minerals and salts that are dissolved in your pee, especially if you haven't been drinking enough water. You may or may not have symptoms. If you do, the most common symptom is flank pain, which can be severe. Most kidney stones pass on their own, but if they don't, your doctor can use a few techniques to help break up the stones so you can pass them more easily. One of the best ways to prevent stones is to drink enough water every day.
Kidney Stones FAQs
Can children get kidney stones?
Yes, children can get them, too. More kids are getting them because more children have risk factors for them, such as diabetes, obesity, and high blood pressure. Kids who get kidney stones often have a metabolic or neurologic condition or were born with an abnormality in their urinary system.
How long does it take to pass a kidney stone?
That depends on the size of the stone and where the stone is located. It can take 1-2 weeks to pass a smaller stone and may take 3 or more weeks for a larger stone.
Are kidney stones dangerous?
Kidney stones alone aren't generally dangerous. However, if you don't pass your stones, you may get complications, such as UTIs or kidney infections, that can be dangerous. They can also be extremely painful. If you think you may have kidney stones, you should go see your doctor. They can do tests to see if you need help removing your stones or if they're likely to pass on their own. They can also prescribe medicines to ease pain and help you pass your stones more easily.
