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Kidney stones

 

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 

The kidneys are two bean-shaped organs that are roughly four inches in length. They are located towards the back of the abdomen (stomach) on either side of the spine.

The kidneys remove waste products from the blood and transfer them into the ureter, along with excess fluids. The ureter is the tube that attaches each kidney to the bladder. From there, the waste products and excess fluid are disposed of as urine. The clean blood is then transferred back into the body.

Kidney stones

The waste products in the kidneys can occasionally form crystals that collect around the inside of the kidney. Over time, the crystals may build up to form a hard stone-like lump. This is a kidney stone.

There are four main types of kidney stone. See Kidney stones - symptoms for more information about the different types of kidney stones.

How common are kidney stones?

Kidney stones are quite common and usually affect people who are between 30 and 60 years of age. They affect men more than women. It is estimated that renal colic (severe pain caused by a kidney stone) affects about 10-20% of men, and 3-5% of women. 

Outlook 

After a kidney stone has formed, your body will try to pass it in urine, so it will often travel through the urinary system. The urinary system produces, stores and removes urine. The urinary system is made up of the kidneys, the ureters, the bladder and the urethra (the tube that carries urine from the bladder to the outside of the body).

While small stones may be passed out in the urine, it is fairly common for a stone to block part of the urinary system, such as the ureter or the urethra. If this happens, it can cause severe pain in the abdomen or groin. A blockage in the urinary system can also lead to:

  • infection
  • kidney damage
  • kidney failure 

There are several procedures to remove, or break down, larger kidney stones. Around half of people who have had kidney stones will experience them again within the following 10 years.

Glossary
Kidney
Kidneys are a pair of bean-shaped organs located at the back of the abdomen. They remove waste and extra fluid from the blood and pass them out of the body as urine.
Abdomen
The abdomen is the part of the body between the chest and the hips.
Spine
The spine supports the skeleton, and surrounds and protects the delicate spinal cord and nerves. It is made up of 33 bones called the vertebrae.
Blood
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Bladder
The bladder is a small organ near the pelvis that holds urine until it's ready to be passed from the body.
Urethra
The urethra is a tube that carries urine from the bladder to the outside of the body.
Pain
Pain is an unpleasant physical or emotional feeling that your body produces as a warning that it's been damaged.
Groin
The groin is the area at the front of the body where the thigh meets the abdomen.

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. This type of kidney stone is known as 'silent' because it is discreet.

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

Common symptoms of kidney stones include:

  • intense pain in the back or side of your abdomen (stomach), or occasionally in your groin, which may last for minutes or hours, with intervals inbetween when there is no pain
  • feeling restless and unable to lie still
  • nausea (feeling sick)
  • blood in your urine, which is often caused by the stone scratching the ureter
  • cloudy or smelly urine
  • a burning sensation when you urinate 
  • a high temperature (fever) of 38°C (100.4°F) or over 
  • feeling like you need to urinate more often, even if you do not need to

Blocked ureter

The ureter is a muscular tube that carries waste products from your kidneys to your bladder. If the ureter becomes blocked by a kidney stone, it may swell up (hydroureter) and cause the muscles to spasm (contract tightly). The spasms can be very painful.

When a stone in the ureter causes severe pain, this is known as renal colic.

If the ureter becomes swollen, you may experience symptoms such as:

  • nausea and vomiting
  • feeling like you need to urinate all the time
  • pain when you urinate

Kidney infection

A blocked ureter can also cause an infection in the kidney because waste products cannot pass, which may cause a build-up of bacteria. Symptoms of an infected kidney include:

  • pain in the lower side of your back
  • a high temperature (fever) of 38°C (100.4°F) or over 
  • shivering
  • nausea and vomiting
  • diarrhoea
  • cloudy and bad smelling urine
  • needing to urinate more often than normal
  • pain when you urinate

See the Health A-Z topic about Kidney infection for more information about this condition.

Types of kidney stones

There are four main types of kidney stones:

  • calcium stones are made from calcium and phosphate, or calcium and oxalate
  • 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.

The exact cause of kidney stones cannot always be found, although they are usually formed following a build-up of a substance in the body, such as:

  • calcium: a mineral that helps build strong teeth and bones
  • ammonia: a colourless gas with a strong smell
  • uric acid: a waste product that is produced when the body breaks down food to use as energy
  • cystine: an amino acid that helps build protein 

Certain medical conditions, such as cancer or kidney disease, can also increase your risk of developing kidney stones. This is usually due to the treatment for these conditions.

You are 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 previously, particularly if this was before you were 25 years of age
  • 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 also evidence that certain types of medication may also increase your risk of developing recurrent kidney stones. For example:

  • aspirin
  • antacids
  • calcium and vitamin D supplements 

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

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 due to factors such as:

  • high levels of vitamin D
  • an overactive parathyroid gland (your parathyroid glands help to regulate the amount of calcium in your body and release hormones)
  • kidney disease
  • sarcoidosis (a condition that causes inflammation of the lymph nodes and other organs)
  • some cancers

Calcium stones are usually either large and smooth, or spiky and rough.

Struvite stones

Struvite stones are often caused by infections, and they most commonly occur after a urinary tract infection (UTI) 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 that prevents the body breaking down chemicals, such as gout
  • an inherited condition that causes higher levels of acid in the body
  • chemotherapy (a treatment for cancer)

Cystine stones

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.

Glossary
Bypass
A bypass is when the flow of blood or other fluid is redirected, permanently because of a blockage in the body, or temporarily during an operation.
Dehydrated
Dehydration is an excessive loss of fluids and minerals from the body.
Thyroid
The thyroid is a jointed piece or cartilage that encloses the vocal cords and forms the 'Adam's apple' in men.
Lymph nodes
Lymph nodes are small oval tissues that remove unwanted bacteria and particles from the body. Part of the immune system.
Chemotherapy
Chemotherapy is a treatment of an illness or disease with a chemical substance, for example, in the treatment of cancer.
Antacids
Antacids are medicines that counteract or neutralise acidity in the lining of the stomach, used to treat indigestion and heartburn. For example magnesium carbonate and calcium carbonate.
Diuretics
Diuretic medicine increases the production and flow of urine from the body, used to remove excess fluid from the body.
Inflammation
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
Kidney
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.
Genetic

Genetic is a term that refers to genes, which are the characteristics inherited from a family member.

 

Useful Links

Your GP will usually be able to diagnose a kidney stone from:

  • your symptoms
  • your medical history, particularly if you have had kidney stones before 

Your GP may suggest a number of tests including:

  • blood tests to check that your kidneys are working properly, and to check the levels of substances that could cause kidney stones, such as calcium
  • urine tests to check for infections and pieces of stones
  • an examination of any stones that you pass in your urine

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.

Imaging

You may be referred to a hospital for an imaging test. A number of different diagnostic techniques may be used to help confirm the diagnosis, or to identify precisely where a kidney stone is. These include:

  • X-ray: an imaging technique that uses high-energy radiation to show up abnormalities in your body tissue
  • an ultrasound scan, which uses high-frequency sound waves to create an image of the inside of your body
  • computed tomography (CT) scan, which takes a series of X-rays of your body at slightly different angles and uses a computer to put the images together
  • an intravenous urogram (IVU) (also known as an intravenous pyelogram, IVP), where dye that shows up on an X-ray is injected into a vein in your arm so that, as the kidneys filter the dye out of your blood and into your  urine, the X-ray image highlights any blockages

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 at your local primary care trust (PCT). 

Glossary

Bladder
The bladder is a small organ near the pelvis that holds urine until it is ready to be passed from the body.
Pain
Pain is an unpleasant physical or emotional feeling that your body produces as a warning sign that it has been damaged.
X-ray
An X-ray is a painless way of producing pictures of inside the body using radiation.
Blood
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Vein
Veins are blood vessels that carry blood from the rest of the body back to the heart.
Kidneys
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.
Intravenous
Intravenous (IV) means the injection of blood, drugs or fluids into the bloodstream through a vein.

If you have a kidney stone, the type of treatment that you will need will depend on the type of kidney stone that you have.

Small kidney stones

Most kidney stones will be small enough to be passed in your urine, and it may be possible to treat these at home. For stones up to 4mm (0.2in) in diameter, eight out of ten people will be able to pass them in their urine.

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.

Medication

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.

Self care

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. 

See the box to the right for advice about when to seek urgent medical attention if you are treating your kidney stones at home.

Large kidney stones

If a kidney stone is too big to be passed naturally, you may need to have treatment to remove it another way. If your stone is 6-7mm (0.3in) in diameter, or larger, you may require treatment. This could include:

  • extracorporeal shock wave lithotripsy (ESWL)
  • percutaneous nephrolithotomy (PCNL)
  • ureteroscopy
  • 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)

Extracorporeal shock wave lithotripsy (ESWL) is the most common way of treating kidney stones that cannot be passed in the urine.

ESWL involves using X-rays (high-energy radiation) or ultrasound (high-frequency sound waves) to pin-point 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 under a local anaesthetic (painkilling medication).

You may need more than one session of ESWL in order to treat your kidney stones successfully. For stones that are up to 20mm (0.8in) in diameter, ESWL is up to 99% effective. 

Percutaneous nephrolithotomy (PCNL)

Percutaneous nephrolithotomy (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 that is called a nephroscope. An incision (cut) that leads to your kidney 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 ESWL.

PCNL is often performed under general anaesthetic, which means that you should not drive or operate machinery for up to 48 hours after the procedure.

As PCNL is a type of surgical procedure, it does carry more risks than ESWL. For stones that are 21-30mm (0.8-1.2in) in diameter, PCNL is 86% effective.  

Ureterorenoscopy 

If a kidney stone is stuck in your ureter (the muscular 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).

Ureterorenoscopy involves passing a long, thin telescope, called a ureteroscope, through your urethra (the tube that carries urine from the bladder to the outside of the body), into your bladder. It is then passed up into your ureter to where the stone is stuck.

The surgeon may either try gently to remove the stone using another instrument, or they may use lasers, or ESWL, to break the stone up into small pieces so that it can be passed naturally in your urine.

As with PCNL, ureterorenoscopy is also 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.

Surgery

If none of the methods for removing your kidney stone that are described above are suitable, it may be necessary to remove it using traditional surgery. This will involve making an incision (cut) in your back in order to gain access to both your ureter and your kidney. The kidney stone can then be removed.

This kind of surgery is only necessary in around 5% of cases. 

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.

When to seek urgent medical attention

If your GP recommends that you can be treated at home, there are some symptoms that you should look out for. 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 sudden, severe pain

If you experience any of the above symptoms, contact your GP immediately for advice.

Admission to hospital

If your kidney stone has moved into your ureter, and it is causing severe pain, your GP may recommend that you are admitted to hospital for treatment. Some of the reasons that you may be admitted to hospital include:

  • if you are at increased risk of your kidneys failing, for example, because you only have one kidney
  • if your symptoms do not improve within an hour of being given painkillers or anti-sickness medication
  • if you are dehydrated (the normal water content of your body is reduced) and you are vomiting too much to keep fluids down
  • if you are pregnant
  • if you are over 60 years of age

Complications that develop as a result of kidney stones are rare because, in most cases, kidney stones are identified and treated before problems can occur.

However, if a blockage occurs, there is a risk of infection and, in very rare cases, your kidney may be damaged.

Recurring kidney stones

The most common complication is that your kidney stones may reoccur. People who have passed one kidney stone have a 60-80% likelihood of having another one at some point in their life. 

Complications of treatment

The different kinds of treatment for larger stones (see Kidney stones - treatment) may cause some complications. Your surgeon should explain these to you before you have the procedure to remove them.

Possible complications will depend on which treatment you have, and the size and position of your stones. They could include:

  • sepsis: an infection that has spread through the blood, causing symptoms throughout the whole body
  • steinstrasse: steinstrasse is the medical name for a blockage that is 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
  • pain

It is estimated that between 5 and 9% of people may experience complications after having ureterorenoscopy.

Glossary

Kidney
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.
Pain
Pain is an unpleasant physical or emotional feeling that your body produces as a warning sign that it has been damaged.

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.

Normally, you should drink at least six to eight glasses (about 1.2 litres) of water each day. However, people who have had a kidney stone before are encouraged to increase their fluid intake to two to three litres each day in order to 'flush out' waste products that can cause stones to develop.

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.

Diet

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:

  • beetroot
  • asparagus
  • rhubarb
  • chocolate
  • berries
  • leeks
  • parsley
  • celery
  • 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.

Medication

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 previously had a struvite stone, you may need to take antibiotics. Antibiotics will help to prevent bacteria from causing a urinary tract infection (UTI), which will infect your kidney and may create a stone.

Your GP will be able to provide you with more advice about how to prevent UTIs. The Health A-Z topic about UTIs also provides further information and advice.

Glossary

Bacteria
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.
Antibiotics
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.