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Kidney stones are stone-like lumps that can develop in one or both of the kidneys.
The medical name for stones in the kidneys is nephrolithiasis. If the stones cause severe pain, this is known as renal colic.
The kidneys are two bean-shaped organs that are roughly four inches in length. They are found towards the back of the abdomen on either side of the spine.
The kidneys remove waste products from the blood. The clean blood is then transferred back into the body and the waste products are passed out of the body as urine.
Symptoms of kidney stones
Small stones may be passed out painlessly in the urine and may even go undetected. However, it is fairly common for a stone to block part of the urinary system, such as:
- the ureter – the tube connecting the kidney to the bladder
- the urethra – the tube urine passes through out of the body
If this happens, it can cause severe pain in the abdomen or groin and sometimes causes a urinary tract infection.
Read more about the symptoms of kidney stones.
What causes kidney stones?
The waste products in the blood can occasionally form crystals that collect inside the kidneys. Over time, the crystals may build up to form a hard stone-like lump.
This is more likely to happen if you don't drink enough fluids, are taking some types of medication, or have a medical condition that raises the levels of certain substances in your urine.
Read more about the causes of kidney stones.
After a kidney stone has formed, your body will try to pass it out of the body in urine. This means it will often travel through the urinary system (the kidneys, kidney tubes and bladder).
How common are kidney stones?
Kidney stones are quite common and usually affect people aged 30 to 60 years. They affect men more than women.
It is estimated that renal colic affects about 10-20% of men and 3-5% of women.
Treating and preventing kidney stones
Most kidney stones are small enough to be passed in your urine, and it may be possible to treat the symptoms at home with medication.
Larger stones may need to be broken up with X-rays or ultrasound in hospital, or you may need to have them surgically removed.
Read more about the treatment of kidney stones.
It is estimated that up to half of all people who have had kidney stones will experience them again within the following five years.
To avoid getting kidney stones, make sure you drink plenty of water each day so that you don't become dehydrated. It is very important to keep your urine diluted to prevent waste products forming into kidney stones.
Read more about preventing kidney stones.
If you have a kidney stone that is very small, it is unlikely to cause many symptoms. It may even go undetected and pass out painlessly when you urinate.
Symptoms usually occur if the kidney stone:
- gets stuck in your kidney
- starts to travel down the ureter (the tube that attaches each kidney to the bladder), because, as the ureter is a narrow tube, the kidney stone causes pain as it tries to pass through
- causes an infection
In these cases, common symptoms of kidney stones include:
- persistent ache in the lower back, which is sometimes also felt in the groin – men may have pain in the testicles and scrotum
- periods of intense pain in the back or side of your abdomen, or occasionally in your groin, which may last for minutes or hours
- feeling restless and unable to lie still
- nausea (feeling sick)
- needing to urinate more often than normal
- pain when you urinate
- blood in your urine – this may be caused by the stone scratching the kidney or ureter
If a kidney stone causes a blocked ureter, this can lead to a kidney infection. This is because waste products cannot pass, which may cause a build-up of bacteria.
Symptoms of a kidney infection are similar to symptoms of kidney stones, but may also include:
- a high temperature (fever) of 38°C (100.4°F) or over
- feeling very weak or tired
- cloudy and bad-smelling urine
Read more information about Kidney infection.
Types of kidney stones
There are four main types of kidney stones:
- calcium stones
- struvite stones contain magnesium and ammonia, and are often horn-shaped and quite large
- uric acid stones are usually smooth, brown and softer than other forms of kidney stones
- cystine stones are often yellow and resemble crystals rather than stones
Kidney stones come in a variety of shapes, sizes and colours. Some resemble grains of sand while, in rare cases, others can grow to the size of a golf ball.
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Kidney stones are usually formed following a build-up of a substance in the body.
This build-up may be any of the following:
- uric acid (a waste product produced when the body breaks down food to use as energy)
- cystine (an amino acid that helps build protein)
Certain medical conditions can lead to an unusually high level of these substances in your urine.
You are also more likely to develop kidney stones if you do not drink enough fluids.
Recurrent kidney stones
You are at a greater risk of developing recurrent (returning) kidney stones if:
- you eat a high-protein, low-fibre diet
- you are inactive or bed-bound
- kidney stones run in your family
- you have had several kidney or urinary infections
- you have had a kidney stone before, particularly if this was before you were 25
- only one of your kidneys works
- you have had an intestinal bypass (surgery on your digestive system), or a disease of the small intestine, such as Crohn's disease (inflammation of the gut)
There is evidence that certain types of medication may increase your risk of developing recurrent kidney stones. These include:
- calcium and vitamin D supplements
- diuretics (used to reduce fluid build-up)
- certain antibiotics
- certain antiretroviral drugs (used to treat HIV)
- certain anti-epileptic drugs (used to treat conditions such as epilepsy)
Types of kidney stones
Kidney stones can develop as a result of a number of different factors. The causes of the four main types of kidney stone are outlined below.
Calcium stones are the most common type of kidney stone. They are caused when there is too much calcium in the urine. High amounts of calcium could be a result of:
- an inherited condition called hypercalcuria, which leads to large amounts of calcium in urine
- high levels of vitamin D
- an overactive parathyroid gland (your parathyroid glands help to regulate the amount of calcium in your body)
- kidney disease
- a rare disease called sarcoidosis
- some cancers
Calcium stones are usually either large and smooth or spiky and rough.
Struvite stones are often caused by infections, and they most commonly occur after a urinary tract infection that has lasted a long time.
Struvite stones are more common in women than in men.
Uric acid stones
Uric acid stones often form when there is a high amount of acid in your urine. Uric acid stones may be caused by:
- eating a high protein diet that includes lots of meat
- a condition such as gout that prevents the body breaking down certain chemicals
- an inherited condition that causes higher levels of acid in the body
- chemotherapy (a treatment for cancer)
Cystine stones are the rarest form of kidney stone. They are caused by an inherited condition called cystinuria, which affects the amount of acid that is passed in your urine.
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Your GP will usually be able to diagnose kidney stones from your symptoms and medical history (particularly if you have had kidney stones before).
Your GP may suggest a number of tests, including:
- urine tests to check for infections and pieces of stones
- an examination of any stones that you pass in your urine
- blood tests to check that your kidneys are working properly, and to also check the levels of substances that could cause kidney stones, such as calcium
You can collect a kidney stone by urinating through some gauze or a stocking. Having a kidney stone to analyse will make your diagnosis easier, and may help your GP to determine which treatment method will be of most benefit to you.
If your pain is severe and not controlled by painkillers, or if you have a high temperature as well as pain, you may be referred to hospital to see a urologist (specialist in treating urinary problems).
If you are referred to hospital for an imaging test, a number of different techniques may be used. This may be to help confirm the diagnosis, or to identify precisely where a kidney stone is.
These tests include:
- a computerised tomography (CT) scan – this takes a series of X-rays of your body at slightly different angles and uses a computer to put the images together
- X-ray – an imaging technique that uses high-energy radiation to show up abnormalities in your body tissue
- an ultrasound scan – this uses high-frequency sound waves to create an image of the inside of your body
- an intravenous urogram (IVU) or intravenous pyelogram (IVP) – where dye that shows up on X-ray is injected into a vein in your arm so that the X-ray image highlights any blockages as the kidneys filter the dye out of your blood and into your urine
IVUs used to be the preferred imaging method, but now CT scans are thought to be more accurate. The imaging technique you have may depend on what is available in your local hospital.
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When to seek urgent medical attention
You should seek urgent medical attention if:
- you have a high temperature (fever) of 38°C (100.4°F) or over
- you have an episode of shivering or shaking
- the pain gets worse, particularly if it is a sudden, severe pain
If you experience any of the above symptoms, contact your GP immediately for advice. If this is not possible, telephone NHS Direct Wales on 0845 46 47 or your local out-of-hours service.
Most kidney stones will be small enough (no more than 4mm or 0.2in in diameter) to be passed out in your urine. It may be possible to treat these at home.
However, small kidney stones may still cause pain. The pain from smaller kidney stones usually lasts a couple of days and disappears when the stone has been passed.
If you have severe pain, your GP may inject you with a painkiller. A second dose can be given after half an hour if you are still experiencing pain.
Medication can also be injected to treat the symptoms of nausea (feeling sick) and vomiting. This is called an anti-emetic (anti-sickness) medication.
You may also be given a prescription for painkillers, anti-emetics, or both, to take at home.
If you are sent home to wait for your kidney stone to pass, you may be advised to try to collect the stone from your urine.
You can do this by filtering your urine through gauze or a stocking. The stone can be given to your GP to help them determine any further treatment you may need.
You should drink enough water to make your urine colourless. If your urine is yellow or brown, you are not drinking enough.
Admission to hospital
If your kidney stone has moved into your ureter and it is causing severe pain, your GP may admit you to hospital for treatment.
This may be necessary if:
- you are at an increased risk of your kidneys failing (for example, because you only have one kidney)
- your symptoms do not improve within an hour of being given painkillers or anti-sickness medication
- you are dehydrated and you are vomiting too much to keep fluids down
- you are pregnant
- you are over 60 years of age
Treating large kidney stones
If a kidney stone is too big to be passed naturally (6-7mm in diameter or larger), you may need to have treatment to remove it another way.
This could include:
- extracorporeal shock wave lithotripsy (ESWL)
- percutaneous nephrolithotomy (PCNL)
- open surgery
These procedures are explained in more detail below. The type of treatment you have will depend on the size and location of your stones.
Extracorporeal shock wave lithotripsy (ESWL)
ESWL is the most common way of treating kidney stones that cannot be passed in the urine.
It involves using X-rays (high-energy radiation) or ultrasound (high-frequency sound waves) to pinpoint where a kidney stone is. A machine then sends shock waves of energy to the stone to break it into smaller pieces so it can be passed in your urine.
ESWL can be an uncomfortable form of treatment, so it is usually performed after giving painkilling medication.
You may need more than one session of ESWL to treat your kidney stones successfully. ESWL is up to 99% effective for stones that are up to 20mm (0.8in) in diameter.
If a kidney stone is stuck in your ureter (tube that carries waste products from your kidneys to your bladder), you may need to have ureterorenoscopy. Ureterorenoscopy is also sometimes known as retrograde intrarenal surgery (RIRS).
It involves passing a long, thin telescope called a ureteroscope through your urethra (the tube urine passes through out of the body) and into your bladder. It is then passed up into your ureter to where the stone is stuck.
The surgeon may either try to gently remove the stone using another instrument, or they may use laser energy to break the stone up into small pieces so that it can be passed naturally in your urine.
Ureterorenoscopy is performed under general anaesthetic, so you should not drive or operate machinery for up to 48 hours after the procedure.
For stones up to 15mm (0.6in), an ureterorenoscopy is effective in 50-80% of cases.
You may need a plastic tube called a stent to be inserted inside you temporarily to allow the stone fragments to drain into the bladder.
Percutaneous nephrolithotomy (PCNL)
PCNL is an alternative procedure that may be used for larger stones. It may also be used if ESWL is not suitable (for example, because the person being treated is obese).
PCNL involves using a thin telescopic instrument called a nephroscope. An incision (cut) is made in your back. The nephroscope is passed through the incision and into your kidney. The stone is either pulled out or broken into smaller pieces using a laser or pneumatic energy.
It is always performed under general anaesthetic (you are put to sleep), which means that you should not drive or operate machinery for up to 48 hours after the procedure.
PCNL is 86% effective for stones that are 21-30mm (0.8-1.2in) in diameter.
Nowadays, it is rare for people to have open surgery for kidney stones (less than 1% of cases require this type of surgery). It is usually used if there is a very large stone or abnormal anatomy.
It involves making an incision in your back to gain access to both your ureter and your kidney. The kidney stone can then be removed.
Treating uric acid stones
If you have a uric acid stone, you may be advised to drink around three litres of water each day to try to dissolve it.
Uric acid stones are much softer than other types of kidney stone, and they can be made smaller if they are exposed to alkaline fluids.
You may need to take some medication to make your urine more alkaline before the uric acid stone starts to dissolve.
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The most common complication of kidney stones is that they may recur.
Other complications are rare because kidney stones are usually identified and treated before problems can occur. However, if a blockage occurs, there is a risk of infection, which in rare cases can damage your kidney.
Recurring kidney stones
People who have passed one kidney stone are thought to have:
- a 20% chance of having another one within five years
- a 35% chance of having another one within 10 years
- a 70% chance of having another one within 20 years
The best way to help prevent recurring kidney stones is to drink plenty of water every day to avoid dehydration.
Read more about preventing kidney stones.
Complications of treatment
The different kinds of treatment for larger stones may cause some complications. Your surgeon should explain these to you before you have the procedure.
Read more about treating kidney stones.
Possible complications will depend on which treatment you have, and the size and position of your stones. Complications could include:
- sepsis – an infection that spreads through the blood, causing symptoms throughout the whole body
- steinstrasse – this is the medical name for a blockage caused by fragments of stone in the ureter (the tube that attaches each kidney to the bladder)
- an injury to the ureter
- urinary tract infection (UTI)
- bleeding during surgery
It is estimated that 5-9% of people may experience complications after having ureterorenoscopy.
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The information on this page has been adapted by NHS Wales from original content supplied by NHS Choices.
Drink plenty of water
To avoid getting kidney stones, make sure that you drink plenty of water each day to avoid becoming dehydrated. It is very important to keep your urine diluted to avoid waste products forming into kidney stones.
You can tell how diluted your urine is by looking at its colour. The darker your urine is, the more concentrated it is. Your urine is usually a dark yellow colour in the morning because it contains a build-up of waste products that your body has produced overnight.
Drinks such as tea, coffee, and fruit juice can count towards your fluid intake, but water is the healthiest option, and is best for preventing kidney stones developing. You should also make sure that you drink more than the recommended daily amount when it is hot, or when you are exercising, in order to replenish fluids that are lost through sweating.
If your kidney stone is caused by an excess of calcium, you may be advised to reduce the amount of oxalates in your diet. Oxalates prevent calcium from being absorbed by your body, and can accumulate in your kidney to form a stone.
Foods that contain oxalates include:
- almonds, peanuts and cashew nuts
- soy products
- grains, such as oatmeal, wheat germ and wholewheat
You should not reduce the amount of calcium in your diet unless your GP recommends it. This is because calcium is very important for maintaining healthy bones and teeth.
To avoid developing a uric acid stone, you should reduce the amount of meat, poultry and fish in your diet. You may also be prescribed medication to change the levels of acid, or alkaline, in your urine.
If you have a kidney stone, medication is usually prescribed for pain relief, or to prevent infections developing. However, some medication may need to be reviewed by your GP if it is thought to be causing your kidney stone.
The type of medication that your GP prescribes will depend on the type of kidney stone that you have.
For example, if you have:
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- calcium stones – you may be prescribed a diuretic medication if they are caused by hypercalcuria (an inherited condition)
- struvite stones – you may be prescribed antibiotics to help prevent a urinary tract infection or kidney infection, which are the main causes of struvite stones
- uric acid stones – you may be prescribed allopurinol (a medication used to lower uric acid levels) and medication to help alkalise your urine
- cystine stones – you may be prescribed medication to lower levels of cystine in your urine
Last Updated: 21/07/2014 14:01:39