Kidney stones

Expert reviewer Professor Raj Persad, Consultant Urological Surgeon
Next review due December 2022

Kidney stones (or calculi) are hard stones that can form in your kidneys. They can cause severe pain starting in your lower back or side and spreading to your tummy and groin.

Kidney stones are most common between the ages of 30 and 60. Between five and 10 in 100 people have pain from kidney stones at some point in their life.

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, the crystals can build up inside your kidney to form a kidney stone.

Kidney stones are usually made of calcium salts, but can also be made of other substances including uric acid. Most stones are less than 2mm across but they can be over 2cm.

Some kidney stones stay where they’re first formed. But they can move out of your kidney into the tube that carries urine from your kidney to your bladder (the ureter). If they get stuck there, they can cause severe pain, called 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

Up to one in 10 people have kidney stones at some point, but many of these are too small to cause symptoms. Stones can be very painful when they move. Larger stones can get stuck in your ureter and may cause infection. Kidney stone symptoms include:

  • severe pain or aching on one or both sides of your lower back
  • sudden waves of excruciating pain caused by spasms in your ureter – usually in your back below your ribs, moving round to the front of your tummy as far as your groin and genitals
  • blood in your urine which may not be visible – if you see blood in your urine, see your GP
  • sickness or vomiting
  • needing to pass urine frequently or very urgently
  • stinging when you pee
  • feeling feverish and sweaty
  • generally feeling restless and uncomfortable
  • tiredness

The kidney stone pain you have depends on where a stone is, not its size.

These symptoms may be caused by something else. But if you have any symptoms of kidney stones, 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 diagnose kidney stones by asking about your symptoms and examining you. They’ll 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 appendicitis, diverticulitis or ectopic pregnancy, which can have similar symptoms.

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

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

Your GP may recommend more tests to confirm the diagnosis and 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 of the urinary system. Your GP will arrange for you to have these tests quickly if you have signs of infection or only one working kidney.

Tests you may have include the following:

It’s particularly important that your stone is examined if you’ve had kidney stones before, but not for a long time.

Self-management of kidney stones

Your treatment will depend on the size of your stone, how bad your symptoms are and whether you’ve had kidney stones before. Most stones can be treated at home.

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. Your doctor will ask you to strain your urine with a tea strainer, nylon stocking or filter paper. This will help catch the kidney stone if it comes out on its own. It can then be examined to find out what type it is, guide your treatment, and prevent more stones.

How long it takes to pass a stone depends on its size and shape – it’s usually within six weeks. Stones larger than 6mm across 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 three weeks.

Passing a kidney stone is often painful and can make you feel sick. Your GP will usually offer you medicines for pain relief and 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 (rectal medicine). If your pain is very severe, they may give you a painkilling injection.

To help flush out the stone, 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 at home. You may need to stay in hospital or be treated as an out-patient. It depends how bad your symptoms are, the type of treatment you have and on possible complications.

You may need urgent hospital treatment if you:

  • still have pain an hour after taking painkillers or the pain comes back quickly
  • have severe pain that you can’t manage at home
  • develop signs of infection such as a raised temperature or cloudy urine
  • can’t pass urine at all
  • are dehydrated because of sickness
  • have only one working kidney, have had a kidney transplant or other problems with your kidneys
  • are pregnant

Your GP may refer you to hospital if they’re unsure about your diagnosis. You’ll see a urologist, who specialises in identifying and treating conditions of the urinary system. They may want to do more tests and will treat any infection.

After treatment for kidney stones your doctor will want to monitor you. You’ll probably have a check-up every six months to a year to see if you’ve developed any more stones. This may involve a CT scan, urine and blood tests.

Medical expulsive therapy

If your kidney stone is less than 10mm (1cm) across, it may not need to be removed immediately. Your urologist may suggest you try medicines called alpha-blockers. This is called medical expulsive therapy (MET). It works best if your pain is well-controlled, there is no infection and your kidneys are healthy.

MET helps the stone pass out in your urine more quickly by relaxing the muscles in the ureter walls, so your symptoms don’t last as long. It’s particularly good for larger stones.

Your doctor will probably suggest you try MET for a month or so before considering further treatment. You may have mild side-effects, like headaches, dizziness and tiredness. Your doctor will explain that this treatment is ‘off label’, which means that using the medicine for this purpose is allowed, but not what it’s licensed for. Ask your doctor if you have any questions.

Dissolving stones

If you have uric acid stones, your specialist may suggest medicines to dissolve them. These help by changing the pH of your urine, to make it more alkaline (less acidic). You will have to monitor the pH of your urine by testing it with a dipstick and alter the amount of the medicine you take depending on the result.

Kidney stone removal

One in five kidney stones won’t pass without surgical treatment. Your urologist will choose a procedure depending on the size, type, and position of your kidney stone.

You may have another X-ray or scan to check if the stone has moved. You’ll give a urine sample and have 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 a stent or nephrostomy tube. A stent is a hollow tube that reduces pressure on the ureter. A nephrostomy tube is a catheter that drains urine direct from your kidney. 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. There are several different procedures to remove kidney stones, which are described below.

Extracorporeal shock wave lithotripsy (ESWL)

This means using a machine to send shock waves from outside your body to break up the stone. Extracorporeal shock wave lithotripsy (ESWL) doesn’t always work as well as other treatments, but it means less time in hospital and a lower risk of complications.

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 you’ll usually have a sedative and a painkiller. The treatment takes 30 to 60 minutes depending on how big the stone is. You need to lie as still as possible. You should be able to go home within a couple of hours.

The procedure can cause skin blistering or bruising. This should disappear after about a week. You can use skin cream to soothe your skin. You may have some pain and bleeding as you pass the stone fragments. Contact your doctor if this is severe.

You may need to have ESWL more than once to completely get rid of your kidney stones. It 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 means using an instrument called a ureteroscope to remove stones that are stuck in your ureter. A ureteroscope is a narrow, flexible tube that your doctor can see through. They will pass it up through your urethra (the tube carrying urine out of the body), into your bladder and then along your ureter. A device on the ureteroscope breaks up the stone with a laser beam. The surgeon can then remove the broken bits.

If your surgeon can’t pass the ureteroscope into your ureter, they may put in a soft tube (stent) first. This can relieve the obstruction and make it easier to insert the ureteroscope later. You may have a stent in your ureter for 1–2 weeks until it heals.

You usually have ureteroscopy under general anaesthetic, so you’ll be asleep during the procedure.

You can usually leave hospital once you’re passing urine normally, but may be asked to stay overnight. Afterwards, you may have mild burning or bleeding when you pass urine. 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 stone fragments are left.

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 put into your body through small cuts. You may have this procedure if:

  • other methods of removing your kidney stone haven’t worked
  • a stone is causing a serious blockage and infection and needs urgent removal

Your surgeon will put a telescopic instrument called a nephroscope through one or more small cuts in your back and move it towards your kidney. The surgeon can then puncture the kidney where the stone is. They may break up the stone using a laser beam or shock waves before pulling it out. You have PCNL under general anaesthetic and will probably be in hospital for several days.

It can take a couple of weeks to recover fully. Your doctor may put a catheter into your bladder and a tube from your kidney to drain urine after the surgery. You may have blood in your urine for a little while. Contact your doctor if this gets worse, you develop a fever, 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. You will probably have another X-ray or CT scan the day after your surgery to check for remaining stones.

Open surgery

It’s rare to have open surgery to remove kidney stones because of all the newer treatments available that are less invasive. Generally, it’s only used for very large or multiple stones, or when other procedures are unlikely to help or haven’t worked. You may have it if you are severely obese or the kidney is so badly affected by stones that it is no longer working.

Causes of kidney stones

Kidney stones form from a build-up of salts or minerals in your urine. They are more common in men, although more women are now developing them, probably because of lifestyle changes.

You’re more likely to get kidney stones if they run in your family or if you’ve had one before. About half of those who’ve had a kidney stone will have another one within five years. Around one in 10 people who’ve had a kidney stone get them again a lot. Your doctor may advise you to have regular checks to see if further stones are developing.

Some medical conditions increase the chance of developing kidney stones, including:

  • having high levels of calcium in your urine – sometimes this has no known cause but it can happen because of another medical condition such as an overactive thyroid, sarcoidosis, Paget’s disease or Addison’s disease
  • other conditions that can affect the make-up of your urine, including cystinuria, gout, cystic fibrosis and hyperparathyroidism
  • having an abnormal shape or structure of your kidneys or ureters
  • metabolic syndrome – this includes high blood pressure, obesity, high blood sugar, and unhealthy cholesterol levels
  • gastrointestinal conditions that cause diarrhoea and dehydration, such as Crohn’s disease

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, antiviral medicines called protease inhibitors or certain diuretics (water tablets)
  • are taking too many antacids, vitamin C, calcium or vitamin D supplements
  • frequently get urinary tract infections
  • don't drink enough
  • aren’t very active
  • live in a hot, dry climate
  • are very overweight (obese)

Complications of kidney stones

A kidney stone can block your ureter and stop the flow of urine. If this isn’t treated, it can permanently damage your kidneys. You may need to have a tube (stent) put in to bypass the blockage and drain the trapped urine.

A blocked ureter can lead to a severe infection, which may be life-threatening without treatment. Signs of an infection include fever and cloudy urine. It's important to seek medical help straightaway. You may need antibiotics through a drip to clear up the infection quickly.

There can be complications after treatment to remove kidney stones. These vary depending on the type of treatment you have, so ask your specialist for more information.

Prevention of kidney stones

Changes to your diet can help to prevent kidney stones. There is information about diet in the section Below.

Your specialist may suggest medicines that can help. The choice of medicine depends on the type of kidney stone you’ve had. Medicines called citrate salts can make your urine more alkaline and stop the formation of calcium stones. Potassium citrate and sodium bicarbonate can help to prevent uric acid and cystine stones. Treating urinary infections with antibiotics can limit the risk of getting larger stones called staghorn stones.

Kidney stones and your diet

Lifestyle changes can reduce the risk of another kidney stone.

It’s particularly important to drink enough throughout the day to make your urine colourless rather than yellow or brown. This will help to prevent a build-up of some of the minerals that can cause kidney stones. Aim to drink 2 to 3 litres a day. Water is a good choice, but most drinks will count. Limit alcohol as large amounts can dehydrate you. Depending on the type of stone you’ve had, your specialist may recommend cutting down on tea. Eating more liquid foods like soup and stew, or fruit and vegetables that contain water, can also help.

For all types of stones, try to eat less meat and fish and more fruit and vegetables. You should also cut down on your salt intake – don’t add extra to your food and cut down on processed and pre-prepared foods as they often have a high salt content. Losing weight can also help if you’re obese or overweight. As being inactive is a risk factor for kidney stones, it’s a good idea to exercise more. Drink plenty to avoid getting dehydrated if you sweat a lot.

Depending on the type of stone you’ve had, your doctor may advise other changes to your diet, possibly including:

  • cutting down foods with high levels of oxalate – chocolate, tea, rhubarb, spinach and nuts
  • avoiding liver, kidneys, herrings with skin, sardines, anchovies and poultry skin – these increase the amount of uric acid in your urine
  • having normal amounts of calcium in your diet (800 to 1000mg a day) but not taking calcium supplements
  • eating more high-fibre foods such as beans and pulses, vegetables and baked potatoes
  • if you take vitamin C supplements, taking no more than 500 to 1000mg per day. Vitamin C forms oxalate in the body
  • avoiding vitamin D supplements, including fish oils, which can increase calcium absorption

If you have to take calcium and vitamin D for another health condition, like osteoporosis, take supplements with meals not between them. Drink plenty to flush the calcium through your kidneys and bladder.

Frequently asked questions about kidney stones

  • Kidney stones (or calculi) are hard stones that can form in your kidneys 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, the crystals can build up inside your kidney to form a kidney stone.

  • Kidney stones form from a build-up of salts or minerals in your urine. They are more common in men, although more women are now developing them, probably because of lifestyle changes.

    You’re more likely to get kidney stones if they run in your family or if you’ve had one before.

  • Your treatment will depend on how bad your kidney stone symptoms are, the type of treatment you have and possible complications. For example, you may need to stay in hospital or be treated as an out-patient.

    See our Treatment of kidney stones section for more information.

  • 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. You don’t need calcium supplements unless your doctor advises them.

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

  • Kidney stones and gallstones are very different. Gallstones may produce similar symptoms, such as nausea and pain, but are caused by something else. They develop in your gallbladder and are formed by chemicals in bile. This is a fluid your liver makes which is stored in the gallbladder.

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

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  • Reviewed by Laura Blanks, Specialist Health Editor, Bupa Health Content Team and Liz Woolf, Freelance Health Editor
    Expert reviewer Professor Raj Persad, Consultant Urological Surgeon
    Next review due December 2022