Kidney Stones

Kidney Stones Introduction

Kidney stones are stone-like lumps that can develop in one or both of the kidneys. Kidney stones are quite common and, in the UK, they will affect around 3 in 20 men, and 1 in 20 women at some point.

How do the kidneys work?

The kidneys are two, bean-shaped organs that are roughly four inches in length and located towards the back of the abdomen, on either side of the spine. Kidneys work by removing waste products from the blood. The waste products are transferred into the ureter (the tube that attaches each kidney to the bladder) with excess fluids, where it is disposed of as urine. The clean blood is then transferred back into the body.

What is a kidney stone? There are four main types of kidney stone which are outlined below. _ 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.

How does a kidney stone form? The waste products are usually dissolved in the fluids that form urine but, occasionally, they can form crystals which collect around the inside of the kidney. The crystals may gather over time to form a hard stone-like lump. This is a kidney stone. Kidney stones [Section Title] - Health encyclopaedia - NHS Direct Page 1 of 11 After a kidney stone has formed, it will often travel through the urinary system as it tries to be 'passed' in urine. However, it is fairly common for a stone to block part of the urinary system, such as the ureter, or urethra (the tube that carries urine from the bladder to the outside of the body). If this happens, you may experience severe pain in your abdomen or groin. A blockage in the urinary system can also lead to infection, kidney damage or, sometimes, kidney failure.

Symptoms If you have a kidney stone that is very small, it is unlikely to cause many symptoms. It may even go undetected you may pass it painlessly when you urinate. This type of kidney stone is known as 'silent' because they are discreet. Symptoms usually occur if the kidney stone gets stuck in your kidney, if it starts to travel down the ureter, or causes an infection. As the ureter is a narrow tube, you will experience pain if the kidney stone tries to pass through it.

Common symptoms of kidney stones include; _ intense pain in the back, or side, of your abdomen, or occasionally in your groin, _ nausea, _ blood in your urine which is often caused by the stone scratching the ureter, _ cloudy, or smelly urine, _ a burning sensation during urination, and _ fever (a temperature of 38 C or 100.4 F, or higher). If you have kidney stones, you may also feel 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 (renal colic). The spasms can be very painful. If the ureter does swell, you may experience symptoms such as: _ nausea and vomiting, _ feeling like you need to urinate all the time, and _ pain when you urinate. Kidney stones [Section Title] - Health encyclopaedia - NHS Direct Page 2 of 11 A blocked ureter can also cause an infection in the kidney because waste products cannot pass, and this may cause a build up of bacteria. Symptoms of an infected kidney include: _ pain in the lower side of your back, _ fever (a temperature of 38 C or 100.4 F, or higher),

_ shivering, _ nausea and vomiting, _ diarrhoea, _ cloudy and bad smelling urine, _ needing to urinate more often than normal, and _ pain when you urinate.

Causes The exact cause of kidney stones is unknown. They are usually formed following a build up of a substance in the body, such as calcium, ammonia, uric acid, or cystine. 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 also at a greater risk of developing kidney stones if: _ you are dehydrated, or do not drink enough fluids, _ 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, _ only one kidney works, and _ if you have had an intestinal bypass, or a disease of the small intestine, such as Crohn's disease (inflammation of the gut). There is also evidence that certain medication, such as aspirin, antacids, calcium, and vitamin D supplements may increase your risk of developing a kidney stone. Kidney stones can develop as the result of a number of different factors. The causes of the four main types of kidney stone are outlined below

Calcium stones Kidney stones [Section Title] - Health encyclopaedia - NHS Direct Page 3 of 11 The most common type of kidney stone is a calcium stone. These 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, _ kidney disease, _ sarcoidosis (a condition which causes inflammation of the lymph nodes and other organs), and _ some cancers. Calcium stones are usually either large and smooth, or 'spiky' and rough.

Struvite stones Struvite stones are often caused by infections, most commonly occurring after a urinary tract infection that has lasted a long time. Struvite stones are more common in women than 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 encourages higher levels of acid in the body, or _ chemotherapy.

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.

Diagnosis Your GP will usually be able to diagnose a kidney stone from your symptoms. However, 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: Kidney stones [Section Title] - Health encyclopaedia - NHS Direct Page 4 of 11 _ an X-ray, _ ultrasound, _ computerised tomography (CT) scan, or _ an intravenous urogram (IVU), (also known as an intravenous pyelogram (IVP)). An IVU is a technique that involves injecting a dye into a vein in your arm and watching the kidneys filter it out into urine. The dye shows up on an X-ray, which will highlight any points in the filtration process that are blocked. Other tests that may be performed if you have kidney stones include: _ blood tests - to check that your kidneys are working properly, and to check the levels of chemicals that could cause kidney stones, such as calcium, _ urine tests - to check for infections and pieces of stones, and _ examination of any stones that you pass in your urine. You can catch a kidney stone by urinating through some gauze, or a stocking. Having a stone to analyse will make diagnosis easier, it will

enable your GP to determine which method of treatment will benefit you most.

Treatment 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. However, this may still cause pain which may need to be treated using painkillers. If you experience severe pain, you may need to have stronger painkillers and be treated at hospital. The pain from smaller kidney stones usually lasts a couple of days and goes when the stone has been passed.

Large kidney stones If a kidney stone is too big to be passed naturally, you may need treatment to remove it another way. This could include: _ extracorporeal shock wave lithotripsy (ESWL), _ percutaneous nephrolithotomy (PCNL), _ ureteroscopy, or _ surgery. Extracorporeal shock wave lithotripsy (ESWL) Extracorporeal shock wave lithotripsy (ESWL) is the most common way of treating kidney stones that cannot be pass in the urine. ESWL involves using X-rays, or ultrasound, to pin-point where a kidney stone is. A machine then sends shock waves of energy to the stone to break it in to smaller pieces so that it can be passed in your urine. As ESWL can be an uncomfortable form of treatment, it is usually performed under a local anaesthetic.

Percutaneous nephrolithotomy (PCNL) Percutaneous nephrolithotomy (PCNL) involves using a thin telescopic instrument, called a nephroscope, which is passed through an incision in your back, leading to your kidney. The stone is then either pulled out or broken into smaller pieces by a laser, or using 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. Ureteroscopy If a kidney stone is stuck in your ureter, you may need a ureteroscopy. A ureteroscopy involves passing a long, thin telescope, called a ureterscope, through your urethra, into your bladder, and up into your ureter to where the stone is stuck. The surgeon may either gently 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. Kidney stones [Section Title] - Health encyclopaedia - NHS Direct Page 6 of 11 As with PCNL, a ureteroscopy is also performed under general anaesthetic. Since a general anaesthetic is used for this procedure, you should not drive or operate machinery for up to 48 hours after the procedure.

Surgery If none of the other methods of removing your kidney stone are suitable, it may need to be removed using traditional surgery. This will involve making an incision in your back in order to gain access to both your ureter and kidney so that your kidney stone can be removed.

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 compared with 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.

Complications 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 does occur, there is a risk of an infection developing and, in very rare cases, your kidney may be damaged.

Prevention Drink plenty of water You can avoid getting kidney stones by making sure that you drink plenty of water each day, and avoid getting 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 the colour of it. The darker it 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 6-8 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 2-3 litres each day in order to 'flush out' 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. 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, so it can accumulate in your kidney and form a stone. Foods that contain oxalates include: _ beetroot, _ asparagus, _ rhubarb, _ chocolate, _ berries, _ leeks, _ parsley, _ celery, _ almonds, peanuts and cashew nuts, _ soy products, and _ grains, such as oatmeal, wheat germ, and whole wheat. You should not reduce the amount of calcium in your diet unless your GP recommends it. To prevent 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 from 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 to prevent bacteria from a urinary tract infection infecting your kidney and creating a stone. Your GP will be able to give you more advice about how to prevent urinary tract infections. See the 'related articles' section for further information about urinary tract infections.