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Kidney stones

Kidney stones (or calculi) are hard stones that can form in one or both of your kidneys. They can cause severe pain in your lower back or side, known as renal colic.

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.

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 into 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, and can vary in size.

Kidney stones 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.

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Extracorporeal shockwave lithotripsy (ESWL)
A procedure that uses high-energy shockwaves to break down kidney stones
An image showing the location of the bladder and surrounding structures


  • Symptoms Symptoms of kidney stones

    Many kidney stones are too small to cause symptoms. However, larger stones can get stuck in your ureter – the tube that leads from your kidney to your bladder. 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 move down and around to the front of your abdomen (tummy)
    • blood in your urine
    • feeling sick or vomiting
    • needing to pass urine more often or very urgently; it may also sting as you pass urine

    The pain of kidney stones – called renal colic – can be very severe. Where you feel the pain depends on how far down your ureter the stone has travelled before it gets stuck. If the blockage is in your kidney or upper ureter, you will probably feel pain in your lower back or sides. If the stone has blocked the lower end of your ureter you may feel pain going down to your groin or genitals.

    The pain may wake you up when you’re asleep and may last for between three and 18 hours. It tends to be continuous, but you may find you have waves of more severe pain as well. The severity of the pain you feel doesn’t depend on the size of the stone, but on where it causes a blockage.

    If you have any symptoms of kidney stones, you should contact your GP. If you have severe pain, you may need to get urgent medical attention.

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  • Diagnosis 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. If your GP suspects you have kidney stones, they will 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 will also usually ask you to have a blood test. This is to check for infection and to measure the levels of certain minerals in your blood that cause kidney stones. The blood test will also be able to assess 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. 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 intravenous urogram (IVU) – this uses a special dye that shows up your urinary system and any stones on X-ray images. You may be offered an IVU if a CT scan isn’t available in your hospital.
    • An ultrasound scan – this uses sound waves to produce an image of your kidneys and urinary system.
    • An X-ray – stones that contain calcium usually show up white on X-ray images.

    Your GP may also ask you to catch the kidney stone by passing your urine through filter paper or a tea strainer. The stone can then be analysed to find out what type it is, to help guide your treatment and prevent more stones.

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  • Treatment Treatment 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. Home treatment If you’re not in too much pain and don’t have any other complications, you can usually wait for your kidney stone to pass in your urine, at home. However, you may need some pain relief, and your GP will usually offer you medicines to reduce pain and sickness. They may also suggest you drink enough fluids to help flush out the kidney stone.

    Hospital treatment

    You may need to be admitted to hospital instead of being treated at home if you:

    • are still having pain an hour after taking painkillers, or the pain comes back
    • have pain which is too severe to deal with at home
    • develop signs of an 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
    • are pregnant

    If you’re admitted to hospital, you will see a urologist – a doctor who specialises in identifying and treating conditions that affect the urinary system. If your urologist thinks you may have an infection, they’ll prescribe antibiotics for you.

    If your kidney stone is less than 10mm (1cm) and doesn’t need to be removed immediately, your urologist may suggest you try medicines called alpha-blockers. These help the stone pass out in your urine. This is called medical expulsive therapy (MET).

    If your kidney stone is too large to pass out in your urine by itself, your urologist may advise you to have a procedure to remove it. The procedure you’re offered will depend on the size and position of your kidney stone. Procedures to remove kidney stones include the following.

    Extracorporeal shock wave lithotripsy (ESWL)

    Extracorporeal shock wave lithotripsy (ESWL) is often the first procedure your urologist will recommend, if it’s suitable for the type of stone you have. In this procedure, your doctor will use a machine to send shock waves through the skin of your abdomen (tummy) to your kidney stone. This breaks the stone up 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.

    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.

    Video showing extracorporeal shockwave lithotripsy
    Play video
    Extracorporeal shockwave lithotripsy (ESWL)
    A procedure that uses high-energy shockwaves to break down kidney stones

    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 pass a narrow, flexible instrument called a ureteroscope up through your urethra (the tube through which you pass urine), your bladder and your ureter. A laser beam or shock waves from a device on the ureteroscope remove or break up the stone. Occasionally, if your surgeon isn’t able to pass the ureteroscope into your ureter, he or she may insert a soft tube (stent) first. This can help to relieve the obstruction and make it easier to insert the ureteroscope later.

    A stent may be left in your ureter for a few days until it heals. Ureteroscopy is usually done under general anaesthesia. This means you will 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.

    Percutaneous nephrolithotomy (PCNL)

    This is a type of surgery that can be used to remove large stones from your kidney or upper ureter. You might also have this procedure if the other surgical methods of removing kidney stones haven’t worked for you. Your surgeon will make a small cut in your back and pass a telescopic instrument called a nephroscope in towards your kidney. This allows your surgeon to pull the stone out or break it up using a laser beam or shock waves. PCNL is carried out under general anaesthesia.

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  • Causes Causes of kidney stones

    Kidney stones form when there’s a build-up of salts or minerals in your urine. You may be more likely to get them if you:

    • have a family history of kidney stones
    • are aged between 30 and 50
    • have a condition called hypercalciuria, in which you have unusually high amounts of calcium in your urine
    • are taking certain medicines – for example, protease inhibitors (such as indinavir) and certain diuretics (such as triamterene) 
    • are taking too many vitamin C or calcium/vitamin D supplements, or antacids
    • have a condition affecting the shape or structure of your kidney or ureters
    • have metabolic syndrome – this is a combination of several heart disease risk factors, including high blood pressure, obesity, high sugar and unhealthy cholesterol levels
    • don't drink enough fluids
    • have certain conditions, such as hyperparathyroidism, high blood pressure or gout
    • have cystitis – the bacteria that cause this infection can break down a substance found in urine called urea, which can lead to kidney stones

    You’re more likely to get kidney stones if you’re a man. You’re also more likely to get a kidney stone if you’ve had one before.

  • Complications Complications of kidney stones

    A kidney stone that completely blocks your ureter (the tube that carries urine from your kidney to your bladder) can stop the flow of urine. This would cause permanent damage to your kidneys if you didn’t get it treated.

    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.

  • Prevention Prevention of kidney stones

    If you’ve had a kidney stone, your doctor will probably advise you to increase the amount of water you drink, to reduce your risk of getting another one. You should be drinking enough fluid to make your urine colourless rather than yellow or brown.

    If you’ve had a calcium stone, your doctor may also advise you to do 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.
    • Cut down on foods that have high levels of oxalate – such as chocolate, tea, rhubarb, spinach, nuts and strawberries.
    • Eat less meat, fish and poultry. Liver, kidneys, herrings with skin, sardines, anchovies and poultry skin increase the amount of uric acid in your urine.
    • Don’t take vitamin C supplements of more than 500 to 1000mg per day because vitamin C forms oxalate in the body. You should also steer clear of vitamin D preparations, including fish oils and multivitamins. These can increase how much calcium you absorb.

    Depending on the types of kidney stone you get, your GP may prescribe various medicines to help prevent further stones.

  • FAQs FAQs

    I have been told that kidney stones are caused by drinking too much milk and eating too many foods that contain calcium. Is that true?


    No, it isn't true. In fact, not eating enough calcium can make you more likely to develop a kidney stone. It's important to eat a healthy, balanced diet that contains some calcium.


    Four out of five kidney stones are made from calcium – either calcium oxalate or calcium phosphate. So you might think that it would be good to restrict the amount of calcium you eat if you want to avoid getting kidney stones. But it seems that eating a low calcium diet makes it more likely that you’ll get stones. This is because a low calcium diet makes you absorb more oxalate, which can then lead to kidney stone formation.

    To stay healthy, it's important to eat a balanced diet that contains some calcium. Examples of foods that are rich in calcium include dairy products such as milk and cheese and leafy green vegetables. Don't take calcium supplements unless your GP or urologist advises you to.

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

    Speak to your GP, urologist or dietitian for advice before making any major changes to your diet.

    How can I control the pain when passing a kidney stone?


    Kidney stones can be very painful. Depending on how severe your pain is, there are a number of different painkillers that your GP or a urologist can prescribe for you.


    The pain you get with a kidney stone can become severe, usually when the stone causes a blockage in your ureter. This is the tube that carries urine from your kidney to your bladder. The pain often starts slowly but gets worse and worse. It may be in your lower back and sides, sometimes spreading around and down to your groin.

    If you’re not in too much pain and don’t have any other complications, your GP may recommend you stay at home and wait for the kidney stone to pass naturally.

    Your GP will usually prescribe you a non-steroidal anti-inflammatory drug (NSAID), such as diclofenac, or naproxen to help you manage the pain at home. You may be given tablets to take by mouth or suppositories to be inserted into your rectum (back passage). 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 of painkiller. You may also be offered an anti-sickness medicine if you need it.

    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).

    Does having a kidney stone make me more likely to have another one?


    Yes. Once you’ve had a kidney stone, you're more likely to get another, compared to someone who has never had one. You can reduce your risk of having another kidney stone by drinking plenty of fluids every day and making some changes to your diet.


    Around one in seven people who have a kidney stone go on to develop another one within a year. One in three people develop another kidney stone within five years of the previous one. But there are things you can do to help reduce your risk of getting another stone. Drinking enough fluids can help to keep your urine watered down. This helps to prevent a build up of some of the minerals that can cause kidney stones. You're aiming for your urine to be colourless, rather than a yellow colour.

    Eat a healthy balanced diet, without too much salt or animal protein, such as meat and fish. If your previous kidney stone was caused by certain minerals, your GP or urologist may ask you to avoid certain foods in your diet. This can help to cut down the amount of these substances in your body and reduce your risk of having another kidney stone. Don't change your diet without advice from your GP, urologist or a dietitian.

    Depending on the kind of stone you have had, and what caused it, you may need to take medicines that help to prevent another stone forming.

  • Resources Resources

    Further information


    • Kumar P, Clark M. Clinical medicine. 8th ed. Edinburgh: Saunders; 2012
    • Nephrolithiasis. BMJ Best practice., published 6 September 2013
    • Nephrolithiasis. Medscape., published 28 April 2014
    • Urinary tract stones (urolithiasis). PatientPlus., published 13 August 2012
    • Urinary calculi. The Merck Manuals., published July 2014
    • Renal colic – acute. NICE Clinical Knowledge Summaries., published March 2009
    • McLatchie G, Borley N, Chikwe J. Oxford handbook of clinical surgery. 4th ed. Oxford: Oxford University Press; 2013
    • Map of Medicine. Kidney stones. International View. London: Map of Medicine; 2013 (Issue 3)
    • Turk C, Knoll T, Petrik A, et al. Guidelines on urolithiasis. European Association of Urology 2014.
    • Kidney stones. The British Association of Urological Surgeons, , accessed 9 January 2015
    • Kidney and bladder stones., published 12 April 2012
    • Lithotripsy for stones. The British Association of Urological Surgeons., published March 2014
    • Ureteroscopic stone removal. The British Association of Urological Surgeons., published March 2014
    • Percutaneous (keyhole) removal of kidney stone(s). The British Association of Urological Surgeons., published March 2014
    • Dietary advice for stone formers. The British Association of Urological Surgeons., published March 2014
    • Calcium. Food Standards Agency., accessed 30 October 2014
    • Indinavir. Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press., accessed 13 November 2014
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