Kidney stones (or renal stones)

What are kidney stones?

Kidney stones are hard masses that form from crystals in your urine when it contains too many waste substances and not enough fluid. They're also called renal stones, and they're common, affecting more than 1 in 10 people at some point in their lives.

Symptoms of kidney stones

Small kidney stones often cause no symptoms at all, and you may pass them painlessly when you pee. Larger stones are more likely to cause symptoms, including:

• pain in your side or lower back, which can spread to your groin and come in waves of severe pain
• feeling sick or being sick
• needing to pee more often, or pain when you pee
• blood in your urine
• cloudy or bad-smelling urine
• a fever or chills, which can be a sign of infection.

Causes of kidney stones and who is at risk

Kidney stones form when waste products in your blood build up as crystals inside your kidneys, usually because there's too little fluid and too much of certain substances, such as calcium, sodium, oxalate or uric acid, in your urine.

You may be more likely to develop kidney stones if you:

• don't drink enough fluids
• eat a lot of meat, protein-rich foods, salt, or sugar
• take vitamin C supplements
• have a family history of kidney stones
• have had stomach or bowel surgery, such as gastric bypass surgery
• take certain medications, such as some diuretics or calcium-based antacids
• have a condition such as gout, diabetes, high blood pressure, inflammatory bowel disease, or a condition that raises the calcium in your urine.

Kidney stones are common, affecting more than 1 in 10 people, most often between the ages of 30 and 60. If you've had one kidney stone, you have up to a 50% chance of developing another within 5 years.

Are there different types of kidney stones?

Yes, kidney stones are grouped by the crystals they're made from:

• Calcium stones: The most common type, making up around 4 in 5 cases – they form when your urine has too much calcium, oxalate or phosphate
• Uric acid stones: Often linked to gout, diabetes, or eating a lot of animal protein
• Struvite stones: Caused by urinary tract infections, which can grow quickly into a large 'staghorn' stone that fills part of the kidney
• Cystine stones: A rare type caused by an inherited condition called cystinuria.

If you pass a stone, or have one removed, your doctor can analyse it to find out which type you have, which helps guide your treatment and prevention plan.

How kidney stones are diagnosed

Your doctor will ask about your symptoms and medical history, and you'll usually have a urine test to check for blood, crystals or signs of infection.

You may also have blood tests to check your kidney function and calcium levels, and imaging such as an X-ray, ultrasound or CT scan to see the size, shape, location and number of your stones.

How kidney stones are treated

Non-surgical treatment

Most kidney stones are small enough to pass naturally in your pee, which can take a few weeks. To help this happen, your GP may recommend:

• drinking plenty of fluids, up to 3 litres a day, keeping your urine pale in colour
• painkillers, such as anti-inflammatory medicines, to manage the pain
• anti-sickness medicine, if needed
• alpha-blockers, medicines that relax the ureter to help the stone pass.

Around 90% of small stones (under 6mm) and 60% of larger stones pass on their own without further treatment.

Ask your doctor before taking ibuprofen, since it can occasionally increase the risk of kidney problems during a stone episode.

Surgical treatment

If a stone is too large to pass, is blocking your urinary tract, or hasn't passed within 4 to 6 weeks, your doctor may recommend a procedure to break it up or remove it:

• Shockwave lithotripsy: This uses shockwaves from outside your body to break the stone into smaller pieces that you can pass in your pee; you may need more than one session
• Ureteroscopy: This is where a thin telescope is passed through your urethra and bladder to reach the stone, which is then removed or broken up with a laser – this is done under general anaesthetic
• Percutaneous nephrolithotomy: This is where your surgeon reaches the stone through a small cut in your back, for larger or more complex stones – this is always done under general anaesthetic.

Possible complications of these procedures include infection, bleeding and injury to the ureter, so your surgeon will explain the risks that apply to your specific treatment.

When to see a doctor

Contact your GP or NHS 111 immediately if you have:

• severe pain
• a high temperature, or you feel hot, cold or shivery
• blood in your urine.

Go to A&E if your pain is unbearable, or if you haven't passed your stone within 4 to 6 weeks despite trying to.