Kidney stones

Kidney stones (nephrolithiasis) are hard stones that can form in your kidneys. They usually pass out of your body by themselves in your pee (urine). But how easily they pass and how much pain they cause depends on their size and shape. Sometimes you may need hospital treatment to remove them.

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. Sometimes these crystals can build up inside your kidney to form a kidney stone.

Kidney stones are usually made of calcium salts. But they can also be made of other substances, including uric acid – a waste product found in your urine. Most stones are less than 2mm but they can be over 2cm.

Some kidney stones stay where they form. 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, the muscles in the wall of your ureter contract hard to push the stone along. This can cause severe pain, called renal colic (or ureteric colic). Depending on a stone’s size and position, it can make it difficult to pee and lead to infection.

Up to 1 in 10 people have pain from kidney stones at some point in their life. They’re most common between the ages of 40 and 50. Men are twice as likely to develop them than women.

Causes of kidney stones

Kidney stones are caused by a build-up of salts or minerals in your urine. Some things can make you more likely to develop kidney stones. These include:

• a family history of kidney stones
• medical conditions that affect levels of chemicals in your urine, such as cystinuria, gout, cystic fibrosis, sarcoidosis, and hyperparathyroidism
• your kidneys or ureters being an unusual shape or structure
• gastrointestinal conditions that affect absorption of nutrients, such as Crohn’s disease or previous surgery
• certain medicines or supplements, such as diuretics (water tablets), antacids, vitamin C, calcium or vitamin D supplements
• urinary tract infections (if you get them a lot)
• not drinking enough to keep hydrated
• spending a lot of time in a hot, dry climate
• being very overweight (obese)
• metabolic syndrome, which means having high blood pressure, diabetes, and obesity

Too much salt, refined sugar, meat, or foods that contain oxalate (such as rhubarb, celery, beetroot, spinach, and sesame seeds) in your diet may also affect your risk. Aim to eat a healthy, balanced diet.

Symptoms of kidney stones

Many kidney stones are too small to cause kidney stone symptoms. They may only be discovered by chance, if you have tests for other conditions. But often the first sign of kidney stones is pain, which can come on if the stone moves. Larger stones can also get stuck in your ureter and may cause infection. If you do get kidney stone symptoms, they may include the following.

• Seeing blood in your urine.
• Pain or aching on one or both sides of your lower back.
• Sudden waves of severe pain, known as renal colic. This can spread from your lower back to your groin and genital area. Renal colic can make you feel, or be, sick.
• Needing to pee frequently or very urgently.
• Stinging or burning when you pee.
• Feeling feverish and sweaty.

If you have any symptoms of kidney stones, contact your GP, or if outside of your GP opening hours, dial 111. If you have severe pain and a high temperature, seek urgent medical attention.

Diagnosis of kidney stones

It’s important to see a GP if you have symptoms, such as pain in your side or back. There are several different things it could be, so your doctor will want to examine you. They’ll ask about your symptoms and your medical history. They’ll want to know if you’ve ever had kidney stones before. Your GP may do the following tests.

• They’ll check your tummy (abdomen) for any tenderness and areas that are painful.
• They’ll ask for a urine sample to test for blood and signs of infection.
• Your GP may give you a blood test to check for infection and to measure the levels of minerals that cause kidney stones in your blood. The blood test will also show how well your kidneys are working.
• If your GP suspects kidney stones, they’ll arrange for you to have a scan to confirm the diagnosis. This will help show the size, location, and type of kidney stone. You’ll usually be offered a CT (computed tomography) scan, but you may be offered an ultrasound scan, particularly if you’re pregnant.
• If tests confirm you have a kidney stone, your GP will refer you to a urologist for further tests and to discuss your treatment options. A urologist is a specialist doctor who diagnoses and treats conditions affecting the urinary system. If you have symptoms of renal colic (see the symptoms section above), you may need to have an urgent scan (within 24 hours).

Treatment of kidney stones

You may be able to stay at home while your kidney stone passes, and receive any treatment you need as an outpatient. This means you won’t need to stay in hospital. What kidney stone treatment you have will depend on several things. These include:

• the size of your stone
• where the stone is
• how likely it is to pass on its own
• how bad your symptoms are
• whether you have any other health problems

Sometimes, your doctor will arrange for you to be admitted to hospital for treatment straight away. For example, if your pain is very severe, you have any signs of infection, or you’re dehydrated, or unable to pee. You’ll also usually need to be admitted to hospital if you have a condition that affects your kidney.

Pain relief

Passing a kidney stone is often painful. Whatever treatment you have, one of the first things your doctor will do is help to manage your pain. If your pain isn’t too severe, you can take over-the-counter painkillers, such as ibuprofen, paracetamol, or low-dose codeine. If you need something stronger, your doctor may offer you suppositories (that you insert into your bottom) or injections of painkillers.

Self-management of kidney stones

If your pain is manageable and you don’t have complications, you may be able to wait for your kidney stone to pass in your pee at home. Your doctor will ask you to strain it with a tea strainer or filter paper to help catch the kidney stone. Your doctor may send the stone for testing to find out what type it is, to help prevent any more stones.

How long it takes to pass a kidney stone depends on its size and where it is in your urinary system. It may take up to six weeks. To help pass a kidney stone, make sure you take the pain relief your doctor prescribed and drink plenty of fluids. Your doctor will monitor you and usually arrange to see you again to check whether the stone has passed. If your stone shows no sign of passing, they may recommend treatment to remove your kidney stone.

Medicines

Depending on the type, size, and location of your stone, your GP may be able to offer some medicines to help your kidney stones pass. These may include the following.

• Medical expulsive therapy (MET). These are medicines called alpha-blockers. MET helps the stone pass out in your urine more quickly by relaxing the muscles in the walls of your ureter. Your doctor may suggest it if your stone is larger than 5mm across, but less than 10mm.
• Alkalinisation therapy. If you have uric acid kidney stones, your specialist may suggest medicines such as potassium citrate or sodium bicarbonate to dissolve them. These help by changing the pH of your urine, to make it more alkaline (less acidic).

Kidney stone removal

Your doctor may recommend a procedure to remove your kidney stone if your pain is severe or you have an infection in your kidney. Your doctor may insert a stent or nephrostomy tube before your kidney stone procedure. A stent is a hollow tube that reduces pressure on the ureter (the tube your urine passes through). A nephrostomy tube is a catheter that drains urine direct from your kidney. Both will relieve pain as well as ease any blockage.

There are several different procedures to remove kidney stones. Your urologist will advise which one is best for you, depending on the size, type, and position of your kidney stone. Kidney stone treatments include the following.

• Extracorporeal shock wave lithotripsy (ESWL). This involves using shock waves to break up the stone into fragments, which can then be passed in your urine.
• Ureteroscopy. This laser treatment for kidney stones uses a narrow, flexible instrument called a ureteroscope passed up through your urethra. It breaks up the stone with a laser beam.
• Percutaneous nephrolithotomy (PCNL). This is keyhole surgery using a telescopic instrument called a nephroscope to remove large stones from your kidney or upper ureter. The nephroscope is inserted through a small cut in the skin of your back or side to reach your kidney. Laser or ultrasound is then used to break up and remove the stone.

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 also lead to infection, which can be life-threatening without urgent treatment. Signs of an infection may include a fever. It's important to seek medical help straight away. 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

There are things you can do to reduce your risk of developing kidney stones. Aim to:

• drink enough to keep hydrated (around 2.5 to 3 litres a day) – you could add some lemon juice to your water to further reduce your risk
• eat a healthy diet and limit the amount of salt in your diet (have no more than 6g a day – about a teaspoon)
• maintain a healthy weight and do some physical activity

If you’ve already had a kidney stone, your doctor can give you advice on how to prevent kidney stones coming back. They may recommend medicines to reduce your chance of developing another one.

• Potassium citrate can make your urine more alkaline and stop calcium stones forming.
• Thiazide diuretics can also be helpful if you also have a raised calcium level in your urine.

Changes to your diet

Your doctor will also advise you to make some changes to your diet after having a kidney stone.

The most important thing is to increase your fluid intake. You should drink at least 2.5 to 3 litres a day. This is the same as five-to-six-pint glasses or five-to-six average-sized water bottles. Keep drinking throughout the day. You can have tea, coffee, and alcohol in moderation.

But it’s better if most of your fluid is water or squash. It’s better to not have fizzy drinks. Try adding fresh lemon juice to your water – it acts as a natural stone inhibitor.

Other changes to your diet that your doctor may advise include the following.

• Reduce the amount of animal protein (mainly meat) you eat.
• Try to include more fruit and vegetables in your diet, as well as fibre.
• Cut down on your salt intake – don’t add extra salt to your food and cut down on processed and pre-prepared foods.
• Lose weight if you’re obese or overweight. It’s important to keep physically active too.

Depending on the type of stone you’ve had, your doctor may give you some more specific advice on foods to avoid. This may include the following.

• If you have calcium oxalate stones, avoid foods with high levels of oxalate, including chocolate, tea, coffee, rhubarb, spinach, and nuts.
• If you have uric acid stones, avoid foods high in purines, including liver, kidneys, herrings, sardines, anchovies, and poultry skin.

There’s no need to restrict calcium in your diet. In fact, not having enough calcium can make you more likely to develop a stone. It’s best not to take calcium supplements though, so you can maintain the right level in your body from diet alone. If you already take calcium supplements for some other reason, make sure you drink enough fluids to flush the calcium through your kidneys and bladder. For some types of stone, your doctor may also recommend you avoid vitamin D and high-dose vitamin C supplements.