Kidney stones

Expert reviewer, Professor Raj Persad, Consultant Urological Surgeon
Next review due July 2020

Kidney stones (or calculi) are hard stones that can form in one or both of your kidneys. They may cause renal colic. This is severe pain that starts in your lower back or side then spreads to your abdomen (tummy) and groin. Stones come in different shapes and sizes and are made of salts and minerals that build into crystals.

Kidney stones are common – five to 10 in 100 people are affected by pain associated with kidney stones at some point in their life.

Most people who get kidney stones for the first time are aged between 20 and 50.

An image showing the location of the bladder and surrounding structures

About kidney stones

Most people have two kidneys, which ‘clean’ your blood by filtering out water and waste products to make urine. Kidney stones can form when there’s a build-up of salts or minerals in your urine. These minerals form crystals, which are often too small to notice and pass harmlessly out of your body. However, over time, the crystals can build up inside your kidney to form a kidney stone.

Most kidney stones (about four out of five) are made up of calcium salts (calcium oxalate or calcium phosphate or both). They can also be made up of other substances including uric acid, cystine and struvite. They vary in size from very small stones under 2mm to large ones over 1cm.

Kidney stones may stay where they’re first formed. But they can move out of your kidney into your ureter – the tube that carries urine from your kidney to your bladder. If they get stuck in your ureter, they can cause severe pain, known as renal colic. Depending on a stone’s size and position, it can stop you passing urine easily and lead to infection.

Symptoms of kidney stones

Many kidney stones are too small to cause symptoms – one in 10 people have them without knowing. However, it can be painful when stones move. And larger stones can get stuck in your ureter. This can cause symptoms such as:

  • severe pain or aching on one or both sides of your lower back
  • sudden spasms of excruciating pain – these usually start in your back below your ribs and can move around to the front of your abdomen (tummy) as far as your groin and genitals
  • blood in your urine (this may or may not be visible)
  • feeling sick or vomiting
  • needing to pass urine more often or very urgently; it may also sting as you pass urine
  • feeling feverish and sweaty
  • finding it hard to get comfy and generally feeling restless
  • feeling tired

Some of these are also signs that a blockage has caused an infection.

Where you feel pain and the type of pain you have depends on where a stone is, not its size. It makes a difference how far down your ureter the stone has travelled before it gets stuck.

The pain – called renal colic – can be very severe and tends to come in waves caused by muscle spasms in the ureter. You may find it helps to keep mobile.

These symptoms might not be caused by kidney stones; they may be from something else. But if you have any symptoms of kidney stones, you should contact your GP. If you have severe pain or a high fever, you may need urgent medical attention.

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Diagnosis of kidney stones

Your GP will usually be able to tell if you have kidney stones by asking you about your symptoms and examining you. They will ask about your medical history and if you’ve had stones before. They will look for signs of dehydration, fever and infection, and check for tenderness and where you’re feeling pain. They may take your blood pressure because low blood pressure can indicate kidney stones. They’ll probably examine your abdomen (tummy) to rule out things like appendicitis, diverticulitis or ectopic pregnancy, which may have similar symptoms.

If your GP suspects you have kidney stones, they’ll test your urine using a ‘dipstick’ to check for signs of infection and blood in your urine. Your urine sample may be sent to a laboratory for further tests.

Your GP may also arrange for you to have a blood test. This is to check for infection and to measure the levels of certain minerals that cause kidney stones. The blood test will also show how well your kidneys are working.

Your GP may recommend you have more tests to confirm the diagnosis and to check the size, location and type of kidney stone. You may need to be referred to a urologist for these tests. A urologist is a doctor who specialises in identifying and treating conditions that affect the urinary system. Your GP will arrange for you to have these tests quickly if you have a fever, or have only one working kidney.

Tests you may have include the following.

  • CT (computed tomography) scan – this uses X-rays to make a three-dimensional image of your kidneys and urinary system. The scan will show the size and location of your kidney stone if you have one.
  • An ultrasound scan – this uses sound waves to produce an image of your kidneys and urinary system. It can be less accurate than a CT scan but is more suitable for children and pregnant women

Your doctor may ask you to use a tea strainer, nylon stocking or filter paper when you pass urine. This will help catch the kidney stone if it comes out on its own (see our section about self-management). It can then be analysed to find out what type it is, to help guide your treatment and prevent more stones.

Analysis of your stone is particularly useful if you’ve had kidney stones before but have been completely free of them for a long time.

Self-management of kidney stones

Your treatment will depend on the size of your stone, the severity of your symptoms and if you’ve had kidney stones before. Most stones can be treated without hospital treatment.

If you’re not in severe pain and don’t have complications, you can usually wait for your kidney stone to pass in your urine, at home. How long this takes will depend on the size and shape of the stone. On average, this is anything between a week and six weeks. Stones above 6mm in diameter usually won’t pass on their own. Your doctor may want to monitor you weekly if you’ve still got symptoms and haven’t passed the stone after six weeks.

It can be painful to pass a kidney stone and make you feel sick. Your GP will usually offer you pain-relief medicines and anti-emetics for the sickness. Usually non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen work well, or paracetamol or codeine if you can’t take NSAIDs. You can buy these painkillers over the counter. If your pain is very bad, or you can’t keep tablets down, your doctor may prescribe suppositories (these release medicine when inserted in your rectum). If your pain is very severe, they may give you a painkilling injection.

You should also drink enough water or other non-alcoholic fluid to keep your urine colourless.

Treatment of kidney stones

Hospital treatment

You may need to have treatment in hospital instead of being treated at home. You may need to stay overnight or be able to go straight home after treatment. It depends on the severity of your symptoms and possible complications.

You’ll probably need hospital treatment if you:

  •  are still having pain an hour after taking painkillers or the pain comes back
  • have pain that is too severe to deal with at home
  • develop signs of infection such as a raised temperature and/or cloudy urine
  • can’t pass urine at all
  • get dehydrated because of nausea or sickness
  • have only one working kidney, have had a kidney transplant or have any problems with your kidneys
  • are pregnant
  • have a condition that affects your immune system

Your GP may refer you to hospital if they’re unsure about your diagnosis. You’ll be assessed by a urologist. A urologist is a doctor who specialises in identifying and treating conditions that affect the urinary system. They may want to do more tests and will treat any infection.

Medical expulsive therapy

If your kidney stone is less than 10mm (1cm) wide, it may not need to be removed immediately. Your urologist may suggest you try medicines called alpha-blockers. Calcium channel blockers are another option. This is called medical expulsive therapy (MET). It works best if your pain is well controlled, you haven’t got an infection and your kidneys are healthy.

MET helps the stone pass out in your urine more quickly, so your symptoms don’t last as long and there’s less risk of complications. It’s particularly good for larger stones, wherever they are. Your doctor will probably suggest you try MET for a month or so before considering further treatment. You may get mild side-effects, like headaches, dizziness and tiredness. Your doctor will talk all of this through with you. They will also explain that using the medicine for this purpose is not part of what it’s licensed for. Doctors are able to do this, and it’s called ‘off label’ use. If you have any questions, ask your doctor.

Kidney stone removal

One in five kidney stones doesn’t pass without surgical treatment. Your urologist may advise a particular procedure to get rid of your kidney stone, depending on its size, type, position and other factors.

They may want to do another X-ray first to check if the stone has moved and take a urine sample. You’ll be given antibiotics to get rid of any infection.

If it’s hard to pass urine because your ureter (the tube your urine passes through) is blocked, your doctor may suggest temporarily inserting a stent or catheter. A stent is a hollow tube that reduces pressure on the ureter. The catheter can drain urine direct from your kidneys. Both will relieve pain as well as easing the obstruction.

Advances in technology mean surgical treatment for kidney stones is now less invasive and safer. You’ll feel less discomfort and recover more quickly.

Procedures to remove kidney stones include the following.

Extracorporeal shock wave lithotripsy (ESWL)

Extracorporeal shock wave lithotripsy (ESWL) is not always the most effective treatment but it means less time in hospital and a lower risk of complications. In this procedure, your doctor will use a machine to send shock waves through the skin of your abdomen (tummy) to your kidney stone. Ultrasound or X-rays pinpoint its exact location.

The shock waves break the stone into fragments small enough to be passed in your urine. You may feel some pain as the stone breaks up, so the procedure is usually carried out under sedation with a painkiller. It takes 30 to 60 minutes depending on how big the stone is. You will need to lie as still as possible. You should be able to go home within a couple of hours.

The procedure may leave your skin slightly blistered or bruised. This should disappear after about a week. You can use skin cream to soothe your skin. You may also get some pain and bleeding as you pass the stone fragments. You should contact your doctor if this is severe.

You may need to have this procedure more than once to completely get rid of your kidney stones. ESWL may not be suitable if you’re pregnant, if your blood doesn’t clot properly or if you get a lot of urine infections. Being obese can make it harder to target the stone. You may need to have medical expulsive therapy afterwards to get rid of any fragments.

Ureteroscopic stone removal

This type of surgery can remove stones that are stuck in your ureter (the tube that carries urine from your kidney to your bladder). Your surgeon will use a narrow, flexible instrument called a ureteroscope. They will pass the ureteroscope up through your urethra (the tube through which you pass urine), into your bladder and then along your ureter. A device on the ureteroscope breaks up the stone with a laser beam or shockwave. The surgeon can then lift the broken bits out.

Occasionally, if your surgeon isn’t able to pass the ureteroscope into your ureter, they may insert a soft tube (stent) first. This can help to relieve the obstruction and make it easier to insert the ureteroscope later.

You may have a stent left in your ureter for a few days until it heals.

Ureteroscopy is usually carried out under general anaesthesia. This means you’ll be asleep during the procedure. If you’ve had a stent, your doctor or nurse will let you know a date to have it removed before you’re discharged. Stents are usually removed under local anaesthesia.

You’ll usually be able to leave hospital once you’re passing urine normally. The ureteroscope – and stent if you’ve had one put in – may leave a little swelling. But this should settle in a few days. Over-the-counter painkillers like ibuprofen can help with any pain. It will take about 10 days for you to recover fully. Your urologist may suggest a follow-up X-ray to check if any fragments of the stone are left.

This type of procedure is suitable for most people, but there’s more risk of complications if you’re severely obese.

Percutaneous nephrolithotomy (PCNL)

This is keyhole surgery to remove large stones from your kidney or upper ureter. Keyhole surgery uses long thin instruments that are inserted into your body via small cuts. You might also have this procedure if other surgical methods of removing kidney stones haven’t worked for you. Keyhole surgery may be necessary if a stone is causing a serious blockage and infection and needs to removed urgently.

Your surgeon will make a small cut in your back and insert a telescopic instrument called a nephroscope towards your kidney. This allows your surgeon to puncture the kidney where the stone is, and pull it out. Or they may break up the stone using a laser beam or shock waves. Percutaneous nephrolithotomy (PCNL) is carried out under general anaesthesia and you’ll probably have to stay in hospital for several days.

It can take a couple of weeks to recover fully. Your doctor may insert a catheter in your bladder and a stent from your kidney to drain your urine after the surgery. You may have a slightly raised temperature and blood in your urine for a little while. Contact your doctor if this gets worse or you have problems or pain passing urine.

This procedure isn’t usually suitable if you’re pregnant. If you take medicines to help prevent your blood clotting (anticoagulants) like aspirin or warfarin, you may need to stop before the procedure. Sometimes it’s not possible to reach stones in every part of the kidney. Your urologist may want to do another X-ray to check.

Open surgery

Open surgery is rarely needed to remove kidney stones. It involves making a large incision (cut) in your skin that will need to be stitched up afterwards and takes several weeks to heal. Generally, open surgery is used only if a stone is very big or there are lots of them, and other procedures haven’t worked. It may be considered for more complicated cases; for example, if you’re severely obese.

Causes of kidney stones

Kidney stones form when there’s a build-up of salts or minerals in your urine. You’re more likely to get them if you’ve had one before or other family members have had kidney stones. People are now getting kidney stones younger, usually between the ages of 20 and 50. And modern lifestyles mean men and women are at similar risk.

There are some medical conditions that increase the chance of developing kidney stones. They include:

  • conditions that affect your urine, such as hypercalciuria, cystinuria, gout, cystic fibrosis and hyperparathyroidism
  • a condition affecting the shape or structure of your kidneys or ureters 
  • metabolic syndrome – this is a combination of several heart disease risk factors, including high blood pressure, obesity, high blood sugar, and unhealthy cholesterol levels
  • gastrointestinal conditions, especially ones that cause diarrhoea and could make you dehydrated, like Crohn’s disease and colitis

Your overall health and lifestyle can make a difference too. You’re more at risk of getting kidney stones if you:

  • are taking certain medicines – for example, protease inhibitors and certain diuretics
  • are taking too many vitamin C or calcium/vitamin D supplements, or antacids
  • frequently get urinary tract infections
  • don't drink enough fluids
  • aren’t very active
  • spend a lot of time in a hot, dry climate
  • are obese and have high body mass index (BMI)

Complications of kidney stones

A kidney stone that completely blocks your ureter can stop the flow of urine. This will cause permanent damage to your kidneys if you don’t get it treated. You may need to have a tube (stent) inserted that bypasses (goes around) the blockage and drains the trapped urine.

If a kidney stone is blocking your ureter, you may develop a severe infection, which can become life-threatening without treatment. Signs of an infection include having a fever and cloudy urine. It's important that you seek medical help straight away if you have these symptoms. You may need intravenous (through a drip) antibiotics to clear up the infection quickly.

Kidney stones themselves can cause infection and can lead to complications after treatment to remove them.

Prevention of kidney stones

Your risk of getting kidney stones increases once you’ve had the first one. One in 10 people repeatedly get further kidney stones. But half of people who’ve had a kidney stone only get another once in their lifetime. It may be around five years before another stone develops.

Depending on the type of kidney stone you’ve had, your doctor (most likely your urologist) may prescribe medicines to help prevent further stones. For instance, medicines called citrate salts can change the level of citrate in your urine and stop the formation of calcium stones. Potassium citrate and sodium bicarbonate can reduce uric acid levels and dissolve uric acid and cystine stones. Treating urinary infections with antibiotics can limit the risk of getting larger stones and ones made of calcium phosphate.

Once you’ve been treated for kidney stones, or they’ve passed on their own, your doctor will want to monitor you. You’ll probably have a check-up after six months then every year to see if you’ve developed any more. This may involve a CT scan and urine tests. Your doctor may want to check your blood to see how your kidneys are working and if you’ve got raised levels of uric acid or calcium.

Kidney stones and your diet

If you’ve had a kidney stone, there are changes you can make to your lifestyle to reduce the risk of getting another one. It’s particularly important to drink enough fluid to dilute your urine so it’s colourless rather than yellow or brown.

Aim to drink 2 to 3 litres a day, preferably of water or squash, and limit tea, coffee and alcohol. Large amounts of alcohol can make you dehydrated.

Try to have a couple of glasses of water before you go to bed and again when you get up in the morning. It doesn’t matter whether this is hard or soft tap water or filtered water. Eating more moist or liquid food, like soup and stew, or fruit and vegetables that contain water, can also help.

Depending on the type of stone you’ve had, your doctor may advise changes to your diet. These may include the following.

  • Cut down on salt to less than 3g of salt a day – don’t add it to your food and don’t eat processed foods or other things with a high salt content like smoked fish and tinned meat.
  • Cut down on foods that have high levels of oxalate – for example, chocolate, tea, rhubarb, spinach, nuts and strawberries.
  • Eat less meat, fish and poultry. Particularly avoid liver, kidneys, herrings with skin, sardines, anchovies and poultry skin – all of these increase the amount of uric acid in your urine.
  • Eat normal amounts of calcium, up to 1000mg a day.
  • Eat more high-fibre foods such as beans or baked potatoes, and less refined carbohydrates like white bread and white rice.
  • Don’t take vitamin C supplements of more than 500 to 1000mg per day because vitamin C forms oxalate in the body.
  • Steer clear of vitamin D preparations, including fish oils. These can increase how much calcium you absorb.
  • If your doctor advises you to increase vitamin C and vitamin D for another health condition, like osteoporosis, take any supplements with meals not between them.

Losing weight can also help if you’re obese or overweight. It’s a good idea to do more physical activity, but drink plenty of fluid to avoid getting dehydrated if you sweat a lot during exercise.

Frequently asked questions

  • No, this isn't true. It's important to eat a healthy, balanced diet with some calcium-containing foods like milk, yoghurt and cheese. A daily calcium intake of up to 1000mg is fine, and you should be able to get that from a normal, varied diet.

    Four out of five kidney stones are made from calcium – either calcium oxalate or calcium phosphate. But this isn’t linked to how much calcium you eat or drink so you shouldn’t restrict your calcium intake. In fact, not eating enough calcium may mean you’ll absorb more oxalate, increasing the risk of developing a kidney stone.

    If you have calcium kidney stones, your urologist may advise you to cut out foods that contain high amounts of calcium oxalate. These include chocolate, spinach, nuts and rhubarb.

    Don't take calcium supplements unless your GP or urologist advises you to. If you do need to take them, it’s better to take them with meals, not on their own.

  • Stones can be more painful when they start to move and it may hurt to pass urine.

    Your GP is unlikely to suggest you wait for the kidney stone to pass naturally if you’re in a lot of pain or there are any complications. They’ll probably advise hospital treatment if the pain’s too severe to cope with at home, particularly if you’re still in pain an hour after taking painkillers.

    Your GP will usually prescribe a non-steroidal anti-inflammatory drug (NSAID) like ibuprofen to help you manage the pain at home. If you can’t take NSAIDs, paracetamol or codeine are other options.

    You may be given medicine in the form of tablets to swallow. Alternatively, your doctor may prescribe suppositories. You insert these in your rectum (back passage) where they dissolve to release the medicine. Always read the patient information leaflet that comes with your medicine and if you have any questions, ask your GP or pharmacist for advice.

    If the tablets or suppositories don’t help manage your pain, your GP may offer you an injection that contains a painkiller. They may also offer you an anti-sickness medicine if you need it, and possibly something for dehydration if you’ve lost a lot of fluid.

    While you’re waiting for the stone to pass, drink enough fluids for your urine to stay colourless. You may also find it helps to keep mobile.

    You may also be in pain for a while after you’ve had treatment to break up the stone. This could be from the procedure itself or from the fragments passing out in your urine. NSAIDs can help but you should contact your doctor if the pain gets worse or doesn’t go away.

    If you’re in too much pain at home, your GP may refer you to hospital. At hospital, you may be offered stronger painkillers, such as opioids (morphine-like medicines).

  • Once you’ve had a kidney stone, you're more likely to get another, compared to someone who has never had one. The type and size of stone you had the first time may make a difference to how often this happens. One in 10 people get them again a lot. But half of people who’ve had a kidney stone may only get another once in their lifetime. And it may be a further five years or so before you develop a stone again.

    Your doctor may advise you to have regular checks to see if further stones are developing. And there are medicines you can take to reduce the risk of certain types of stone forming.

    You can also make lifestyle changes to reduce your risk of getting another stone. Drinking enough fluids will help to prevent a build-up of some of the minerals that can cause kidney stones. You're aiming for your urine to diluted enough to be colourless, rather than a yellow colour.

    Your urologist may advise you to cut down or avoid certain foods in your diet, or to increase others, depending on the type of stone you had before.

    Generally, you should aim to eat a healthy balanced diet, without too much salt or animal protein such as meat and fish, but with normal amounts of calcium.

    You should try to lose weight if you’re obese or overweight, and also be more active.

  • No, gallstones may produce some of the same symptoms, like nausea, but are caused by something else. Gallstones are formed by chemicals in bile. This is a fluid your liver makes.

    The pain from gallstones is different – it can be similar to indigestion or more severe. You’ll mostly feel it in your gall bladder, which is under your rib cage.

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  • Reviewed by Natalie Heaton, Specialist Health Editor, Bupa Health Content Team, July 2017
    Expert reviewer, Professor Raj Persad, Consultant Urological Surgeon
    Next review due July 2020