General questions about kidney stones
What are kidney stones?
The kidneys and urinary tract
The kidneys, ureters, and bladder are part of your urinary tract system which makes, transports, and stores urine in the body. The kidneys make urine which then travels down the ureters into the bladder where it is stored before leaving your body through the urethra.
Most people have two kidneys. Their main function is to regulate the body’s fluid and chemical levels. Healthy kidneys remove waste from the blood through the urine. They control sodium, potassium, and calcium levels in the blood.
Kidney and ureteral stones
Urine contains many dissolved minerals and salts. When your urine has high levels of minerals and salts, kidney stones may form. Kidney stones can start small but can grow larger in size.
Some stones stay in the kidney and do not cause any problems. Other stones will travel down the ureter, known as a ureteral stone. Stones smaller than 6mm may reach the bladder and can typically be passed out of the body in urine. However, if the stone becomes lodged in the ureter, urine flow from the kidney will be blocked and cause pain. If the stone is not passed on its own, surgery may be needed to remove it.
What are kidney stones made of?
DISCLAIMER: Stones come in many different types and colors. How you treat them and prevent new stone formation depends on the type of stone.
Calcium stones are the most common type of kidney stones, making up 80% of stones. Too much calcium in your urine can increase your risk of calcium stones. However, even with normal amounts of calcium in the urine, calcium stones can form for other reasons.
There are two types of calcium stones:
- Calcium Oxalate (most common calcium stone)
- Calcium Phosphate
Uric acid stones
Uric acid stones make up about 5-10% of stones. Uric acid is a waste product that comes from chemical changes in the body. High levels of uric acid can form uric acid crystals that do not dissolve well in acidic urine and form a uric acid stone.
Having acidic urine may come from:
- Chronic diarrhea
- Type-2 Diabetes
- A diet high in animal protein and low in fruits and vegetables
Struvite (infection) stones
Struvite (infection) stones make up about 10% of stones. These stones are related to chronic urinary tract infections (UTIs). Some bacteria can change the normal urine environment, making the urine less acidic and more basic (alkaline). Struvite stones form in alkaline urine. These stones are often large, branched, and grow very fast.
People who get chronic UTIs, such as those with long-term tubes in their kidneys or bladder, or those who are not able to properly empty their bladder due to neurologic disorders (paralysis, multiple sclerosis, and spina bifida) are at the highest risk for developing these stones.
Cystine stones form when high amounts of cystine (an amino acid found in certain foods) are present in the urine. Too much cystine in the urine is known as cystinuria. Cystinuria is a rare, inherited, metabolic disorder when the kidneys do not reabsorb cystine from the urine. Cystine stones often form during childhood.
What are symptoms of kidney stones?
Kidney stones often do not cause any symptoms and can go undiagnosed. When a stone leaves the kidney, it travels to the bladder through the ureters. The stone can become lodged in the ureter, block urine flow out of the kidney, and cause the kidney to swell (hydronephrosis), resulting in pain.
- Sharp, cramping pain in the lower back and side, often moving to the lower abdomen or groin.
- The pain often starts suddenly and comes in waves. It can come and go as the body tries to get rid of the stone.
- Some women have reported that the pain is worse than childbirth labor pains.
- For men, you may feel pain at the tip of the penis
- A feeling of an intense need to urinate
- Urinating more often
- Burning feeling during urination
- Urine that is dark or red due to blood
- Nausea and vomiting
What causes kidney stones?
DISCLAIMER: The causes of kidney stone formation varies from person to person. Consult with your doctor on the best kidney stone care for you.
Low Urine Volume
A major risk factor for kidney stones is constant low urine volume. This may come from dehydrationfrom hard exercise, working or living in a hot place, or not drinking enough fluids. When urine volume is low, urine is concentrated and dark in color. Concentrated urine means there is less fluid to keep salts dissolved. Increasing fluid intake will reduce the salts in your urine. By drinking more fluids, you may decrease your risk of forming stones.
Adults who form stones should drink about 3 liters (or 12 – 8-ounce glasses of fluid) per day. While water is likely the best fluid to drink, what matters most is getting enough fluid.
High levels of calcium in the urine can increase your risk for calcium kidney stones. If you have high urine calcium levels, it may be due to the way your body handles calcium. It is not always due to how much calcium you eat. Lowering the amount of calcium in your diet rarely stops stones from forming.
Studies have shown that restricting dietary calcium can be bad for bone health and may increase kidney stone risk. To lower urine calcium levels, healthcare providers usually do not recommend patients limit dietary calcium, but rather that patients decrease their sodium (salt intake).
A high salt diet can increase your risk for calcium stones. When too much salt passes into the urine, calcium is not able to be reabsorbed from the urine and into the blood.
Reducing salt in your diet lowers urine calcium, making it less likely for calcium stones to form.
Oxalate is a component of the most common type of kidney stone, calcium oxalate. Eating foods rich in oxalate can increase your risk for forming these stones.
See the tab “How can I prevent kidney stones?” to learn more about foods rich in oxalate and how to maintain a low oxalate diet.
A diet high in animal protein, such as beef, fish, chicken, and pork, can increase acid levels in the body and urine. High acid levels make it easier for calcium oxalate and uric acid stones to form. The breakdown of meat into uric acid also increases the chance of both calcium and uric acid stones to form.
Certain bowel conditions that cause diarrhea (such as Crohn’s Disease or Ulcerative Colitis) or surgeries (such as gastric bypass surgery) can increase calcium oxalate kidney stones from forming. Diarrhea may result in loss of large amounts of fluid from the body, lowering urine volume. Your body may also absorb excessive oxalate from the intestine due to poor absorption of calcium resulting in more oxalate in your urine. Both low urine volume and high levels of urine oxalate can increase calcium oxalate kidney stones to form.
If you have any of these conditions and kidney stones, you should discuss this with your healthcare provider.
Obesity can increase your risk for stones as obesity may change the acid levels in the urine, leading to stone formation.
Some medical conditions have an increased risk of kidney stones. Abnormal growth of one or more of the parathyroid glands can cause high calcium levels in the blood and urine, increasing kidney stones risk. Another condition called distal renal tubular acidosis, in which there is acid build-up in the body, can raise the risk of forming calcium phosphate kidney stones.
Some rare, inherited disorders can also make certain types of stones more likely. Examples include cystinuria, which is too much of the amino acid cystine in the urine, and primary hyperoxaluria, in which the liver cannot process or digest oxalate.
Medications / Supplements
Some medications, such as calcium and vitamin C or D supplements, may increase your risk of forming stones. Be sure to tell your healthcare provider all the medications and supplements you take, as these could affect your risk of stone formation. Do not stop taking any of these unless your healthcare provider tells you to do so.
Having a family history of stones, such as a parent or sibling, can increase your risk of having a kidney stone.
Content within askMUSIC is provided by the Urology Care Foundation.
How kidney stones are diagnosed and treated
Kidney stones that do not cause symptoms but are often found on an X-ray, during a routine health exam, are known as “silent” kidney stones. Other patients may have their stones diagnosed when the stone is passing, sudden pain may occur and medical attention is needed.
A stone may also be diagnosed on an ultrasound or CT scan, patients may have symptoms of blood in the urine, known as hematuria, or sudden abdominal or side pain. These imaging tests tell the healthcare provider how big the stone is and where it is located.
DISCLAIMER: The kidney stone prevention methods that are best for you depend on the type of stones you form and/or the results of 24-hour urine testing. The prevention approach you take should be discussed between you and your healthcare provider.
Drink plenty of fluids
Why do I have to drink so much fluid?
Nearly 1 in 7 Americans will suffer from urinary stone disease during their lifetime. Over half will develop at least one recurrence. Non-medical and nonsurgical management is a common treatment for many patients with kidney stones. This involves manipulating urine composition with a goal of decreasing stone promoting risk factors promoting risk factors and increasing protective factors.
One of the most important preventive measures is high fluid intake. Therefore, we recommend that you drink enough fluid to produce 2 to 2.5 liters of urine daily.
How do I know when I am drinking enough fluid?
In general, if your urine is only light yellow or clear, then you are drinking enough fluid. There are several ways you can track your fluid intake.
There is a free iPhone app that can help you keep track of your fluid intake for the day (search “kidney stone app” in the Apple store). In the app, you can choose the fluid goal (say 3 liters or 100 ounces) and set the goal for yourself on the last page of the app. You can choose the units (milliliters, ounces, pints, etc.) and then click on the picture of the drink that you consume.
Most reusable water bottles also have volume indicators that may help you track the amount of fluid you drink. There are also smart water bottles that electronically track the amount of water you drink throughout the day.
Does the type of fluid matter?
The specific fluid that you ingest is important, as well. Cranberry juice has been found to increase the risk of calcium oxalate and uric acid stones. Lemonade has long been considered to have stone preventing properties. Plain water is the least expensive and very effective!
Increase Citrate consumption
Why do I need to take in more citrate?
Citrate is a compound produced by the human body and is absorbed from the diet. It complexes with calcium in urine and prevents calcium crystallization. As such, citrate prevents urinary stone formation.
In many stone-formers, a low level of citrate is a big part of the problem. If your doctor has told you that your 24-hour urine collection revealed low levels of citrate, then they may recommend citrate supplementation.
How do I get more citrate?
Medications exist for citrate therapy. If you and your doctor decide on one, they will provide you with a prescription.
Alternatively, you can drink lots of citric-containing juice. Beverages high in citrate content (in decreasing order) include lemon, raspberry, grapefruit, cranberry, orange, and pineapple juice. As an example, 3 ounces (2 tablespoons = 1 ounce) of reconstituted lemon juice (mixed with water and sugar to taste if desired) contains 63 mEq of citrate. If your doctor recommends citrate supplementation, they will provide you with the mEq of citrate necessary.
Follow a balanced Calcium diet
Why do I have to moderate calcium in my diet?
Calcium is a risk factor for stone formation. Importantly, calcium should not be overly decreased in your diet, even if your 24-hour urine collection revealed high levels of calcium.
How much calcium should I take in?
To help prevent future stone formation, it may be recommended that you decrease calcium in your diet, but not too much. It is recommended you take in 800 – 1200 mg of calcium in your diet each day.
Maintain a low Sodium diet
Why do I have to reduce sodium in my diet?
Sodium is a mineral found in many foods that helps keep normal fluids balanced in the human body. Most people eat foods containing more sodium than they need. Some foods that contain high amounts even though they do not taste “salty.” Dietary levels of sodium are important for people with a history of urinary stones because the excretion of calcium (a constituent of many stones) in the urine is directly related to sodium excretion. Moreover, sodium restriction reduces urinary calcium excretion.
How much sodium can I take in?
If it is recommended by your doctor to maintain a low sodium diet, it is recommended that your sodium intake should be less than 2000 milligrams (2 grams) a day. This means more than just eliminating the salt shaker, and it is important to keep a record of the amount of sodium that you consume every day.
Low Oxalate diet
Why do I have to reduce oxalate in my diet?
Oxalate is a compound both produced by the human body and is absorbed from the diet. It is a known promoter of urinary stone formation. If your 24-hour urine collection revealed high levels of oxalate, then it is recommended that you cut back on high-oxalate foods to prevent future stones.
How much oxalate can I take in?
If it is recommended by your doctor to maintain a low oxalate diet, you should limit your oxalate to 40 to 50 mg each day, or possibly less if recommended by your doctor, using the tables below.
|High-Oxalate Foods and Drinks (more than 10 mg per serving)
|Dark beer, black tea, instant coffee, chocolate milk, cocoa, hot chocolate, ovaltine, juice from high-oxalate fruits, and soy drinks
|Soy cheese, soy yogurt
|Fats, nuts, seeds
|Nuts, nut butters, sesame seeds, tahini, soy nuts
|Amaranth, buckwheat, cereal (bran or high fiber), crispbread (rye
or wheat), fruit cake, grits, taro, wheat bran, wheat germ, whole wheat bread, whole wheat flour
|Blackberries, blueberries, carambola, concord grapes, currents,
dewberries, elderberries, figs, fruit cocktail, gooseberry, kiwis,
lemon peel lime peel, orange peel, raspberries, rhubarb, canned
strawberries, tamarillo, angerines
|Beans (baked, green, dried, kidney), beets, beet root, carrots,
|Soy sauce, marmalade, black pepper (>1 tsp)
|Moderate-Oxalate Foods and Drinks (2-10 mg per serving)
|Draft beer, carrot juice, brewed coffee, cranberry juice, Guinness
beer, Matetea tea, orange juice, rosehip tea, tomato juice, Twinings black currant tea
|Fats, nuts, seeds
|Flaxseed, sunflower seeds
|Apples, applesauce, apricots, coconut, cranberries, mandarin
orange, orange, fresh peaches, fresh pear, pineapples, purple and
Damson plums, prunes, fresh strawberries
|Bagels, brown rice, cornmeal, corn starch, corn tortilla, fig cookie,
oatmeal, ravioli (no sauce), spaghetti in red sauce, sponge cake, white bread
|Artichoke, asparagus, broccoli, brussel sprouts, carrots (canned),
corn fennel, lettuce, lima beans, mustard greens, onions, parsnip,
canned peas, tomato, tomato soup, turnips, vegetable soup,
|Ginger, malt, potato chips, strawberry
The Harvard T.H. Chan School of Public Health has created several materials on how to modify your diet.
Reduced Protein diet
Why do I have to reduce protein in my diet?
When the human body metabolizes animal proteins, several promoters of urinary stone formation are produced. High protein intake can increase urinary levels of calcium and uric acid, as well as decrease urinary citrate.
How much protein can I take in?
We recommend that our patients with a history of stones restrict the amount of protein in their diets. Specifically, you should not exceed more than 80 grams of protein per day.
Treatment depends on the type, location, stone size, and the length of time you have had symptoms. There are different treatments to choose from. It is important to talk to your healthcare provider about what treatment is best for you.
Wait for the stone to pass
You can often wait for the stone to pass on its own. Smaller stones are more likely to pass on their own than larger stones.
Waiting up to 4 to 6 weeks for the stone to pass is safe as long as the pain is: bearable, there are no signs of infection, the kidney is not completely blocked, and the stone is small enough that it is likely to pass. While waiting for the stone to pass, you should drink normal amounts of water. You may need pain medication when there is discomfort.
Certain medications have been shown to help a stone pass. The most common medication prescribed for this reason is an alpha-blocker, like tamsulosin (Flomax). Tamsulosin (Flomax) relaxes the ureter, making it easier for the stone to pass. You may also need pain and anti-nausea medicine as you wait to pass the stone.
Surgery may be needed to remove a stone from the ureter or kidney if the stone fails to pass, the pain is too great to wait for the stone to pass, or the stone is affecting your kidney function.
Small stones in the kidney may be left alone if they are not causing pain or an infection. Some patients choose to have their small stones removed because they are afraid the stone will unexpectedly start to pass and cause pain.
Kidney stones should be removed by surgery if they cause repeated infections or are blocking the flow of urine from the kidney. Surgery usually involves small or no incisions (cuts), minor pain, and minimal time off work.
Shockwave Lithotripsy (SWL)
Shockwave Lithotripsy (SWL) is a procedure used to treat stones found in the kidney and ureter. Shock waves are focused on the stone using x-rays or ultrasound to pinpoint the stone. Repeated firing of shock waves on the stone usually causes the stone to break into small pieces. These smaller stone pieces, pass out in the urine over a few weeks.
Some form of general anesthesia is often given to relief possible discomfort caused by the shock waves and to help control breathing during the procedure. SWL does not work well on hard stones, such as cystine stones, some calcium oxalate and calcium phosphate stones, or very large stones.
You may go home the same day as the procedure and be able to resume normal activities in 2-3 days. A strainer may be sent home with you, to collect the stone pieces as they pass so they can be tested.
Although SWL is widely used and considered very safe, you may experience some side effects such as blood in the urine a few days after treatment. Most stone pieces pass painlessly, however, larger pieces may get stuck in the ureter, causing pain and require additional treatment.
Ureteroscopy (URS) is a procedure used to treat stones in the kidney and ureter. During a URS, a very small telescope called a ureteroscope, is passed into the bladder, up the ureter, and into the kidney. The ureteroscope lets your doctor see the stones without making an incision (cut). General anesthesia is given to keep you comfortable during the URS procedure.
Once your doctor sees the stones, a small, basket-like device grabs the stones and removes them. If a stone is too large to remove in one piece, it may be broken into smaller pieces with a laser.
After stone removal, a healthcare provider may place a temporary stent in the ureter. A stent is a tiny plastic tube that helps the kidney drain urine into the bladder. The tube is completely within the body and does not require an external bag to collect urine.
You may go home the same day and be able to resume normal activities in 2-3 days. If your doctor places a stent, you will need to return to the doctor’s office 4-10 days later to have it removed. Sometimes a string is left on the end of the stent so you can remove it on your own. It is very important that the stent is removed only when your health care provider tells you it is okay. Leaving the stent in for a long period can increase your risk of infection and loss of kidney function.
To learn more information about stent placement and removal, we recommend you read through our patient educational stent pamphlet. Download Patient Stent Pamphlet
Percutaneous Nephrolithotomy (PCNL)
Percutaneous Lithotripsy (PCNL) is the best treatment for large stones that have formed in the kidney. During PCNL, a half-inch incision (cut) is made in the patient’s back or side, just large enough, to allow a rigid telescope called a nephroscope, to be passed into the part of the kidney where the stone is located. A medical instrument is then passed through the nephroscope to break up the stone and remove or suction out any pieces. General anesthesia is given during a PCNL procedure.
After PCNL, a tube is often left in the kidney to drain urine into a bag outside of the body, overnight for up to a few days. You may also stay in the hospital overnight after a PCNL procedure.
Your doctor may choose to do X-rays while you are in the hospital to see if any stone pieces remain. If stone pieces are seen, your doctor may want to look back into the kidney with a telescope again to remove them. You can begin normal activities after about 1-2 weeks.