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Kidney stones are a very painful urologic disorder. They are also very common, affecting 600,000 patients per year. Kidney stones usually pass from the body without any medical assistance from a doctor. There are various techniques to treat stones which do not pass out unaided.
Kidney stones are a solid mass which develops from crystals that separate from urine. The stones build up on the inner surfaces of the kidney. Urine usually contains chemicals that prevent stones from forming, but sometimes these do not work and the stones appear. If the stones are tiny enough, they will travel through the body with urine and pass undetected.
Kidney stones usually contain chemicals such as calcium, which combines with other chemicals such as phosphate or oxalate. The chemicals come from a person's dietary intake and are required to maintain healthy muscles and bones. A rarer form of kidney stone is called a struvite; this is caused by an infection in the urinary tract. The medical term used to describe stones which appear in the urinary tract is urolithiasis.
Doctors are unsure of the exact reason kidney stones appear. Although ingestion of certain foods contributes to kidney stones, it is not believed that any specific food is attributable. If there is a family history of kidney stones, you may be more likely to develop this complaint. There is also a rare hereditary disease called renal tubular acidosis. People with this disease are much more likely to develop kidney stones.
The first sign that you have developed kidney stones will be extreme pain. This occurs when a stone blocks the flow of urine. You will feel a cramping or sharp pain in the kidney area. You may also suffer from vomiting, nausea and pain in the groin area. You may feel the need to urinate more often and a burning sensation may occur when you do.
As the kidney stones move or grow larger, blood may appear in the urine. If you suffer from chills and fever along with the aforementioned symptoms, this is a sign of an infection and a doctor should be called. The doctor will take an x-ray or sonogram. He may also take a computed tomography (CT) scan of the urinary system. These tests will help the doctor make a proper diagnosis.
Drinking plenty of water should help kidney stones to pass through the body. The doctor may also prescribe medications to prevent uric acid and calcium stones from forming. Finally, for more severe cases, extracorporeal shockwave lithotripsy may be used. Shock waves will be passed through the body to break up the stones into small particles which can be passed easily when urinating. Your doctor can advise you on future lifestyle changes which should prevent kidney stones from reappearing.
Kidney stones often have no definite, single cause. A number of factors, often in combination, create the conditions in which susceptible people develop kidney stones.
Kidney stones form when the components of urine — fluid and various minerals and acids — are out of balance. When this happens, your urine contains more crystal-forming substances, such as calcium, oxalate and uric acid, than the available fluid can dilute. At the same time, your urine may be short of substances that keep crystals from sticking together and becoming stones. This creates an environment in which kidney stones are more likely to form.
Most kidney stones contain crystals of more than one type. Types of kidney stones include:
Calcium stones. Most kidney stones are calcium stones, usually in the form of calcium oxalate. High oxalate levels can be found in some fruits and vegetables, as well as in nuts and chocolate. Your liver also produces oxalate. Dietary factors, high doses of vitamin D, intestinal bypass surgery and several different metabolic disorders can increase the concentration of calcium or oxalate in urine. Calcium stones may also occur in the form of calcium phosphate.
Struvite stones. Struvite stones form in response to an infection, such as a urinary tract infection. Struvite stones can grow quickly and become quite large.
Uric acid stones. Uric acid stones can form in people who are dehydrated, those who eat a high-protein diet and those with gout. Certain genetic factors and disorders of the blood-producing tissues also may predispose you to uric acid stones.
Cystine stones. These stones represent only a small percentage of kidney stones. They form in people with a hereditary disorder that causes the kidneys to excrete excessive amounts of certain amino acids (cystinuria).
Other stones. Other, rarer types of kidney stones can occur.
Knowing your type of kidney stone helps to understand what might have caused the stone to form and may give clues as to what you can do to reduce your risk of getting additional 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. 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
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
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.
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. However, if this is not possible, telephone your local out-of-hours service.
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.
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.
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.
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) 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) 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.
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.
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.
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.