Kidney stones Kōwhatu tākihi

Your kidneys act as your blood's filtering system, absorbing the 'good' chemicals and minerals and passing unwanted ones into your wee (urine).

If some chemicals and minerals build up in your kidneys or wee, they can form a stone. Most stones are made of calcium oxalate. 

The stones can be as small as a grain of rice or as large as an apple. They can form anywhere in your urinary system, including:

• your kidneys
• the tubes (ureters) that drain wee from your kidneys
• your bladder.

Stones in the kidney may stay there or travel down the ureter into the bladder. This is when they can cause pain.

Inside view of a kidney with a kidney stone

You may have no symptoms from a kidney stone, especially if it is small or not moving down from the kidney.

When a stone is moving you may have symptoms (renal colic), which can include:

• pain, which sometimes comes in waves — you may feel it most often in your lower back or the side of your tummy
• blood in your wee (your wee can look pink)
• feeling sick and throwing up
• a high temperature (fever), which can happen if you get a urine infection.

If you have any of these symptoms, see your healthcare provider or an after hours healthcare provider as soon as possible. They can organise tests and pain relief. If you are very unwell, you may need to go to hospital.

Kidneys stones are usually caused by a combination of factors. You may have a higher risk if you:

• have dark yellow (concentrated) wee
• eat certain kai (foods), such as those high in salt or animal protein
• have a whānau or personal history of kidney stones
• are overweight
• take calcium and vitamin C supplements
• take some medications used for treating medical conditions, such as kidney disease, cancer or HIV infection.

If your healthcare provider thinks you might have kidney stones, they will ask you about your symptoms and do a physical examination.

They may recommend you have some tests. These can include:

• a blood test to check how well your kidneys are working, check for infections and measure the levels of some chemicals in your blood
• a urine test to check for infections and crystals in your wee
• a CT scan or x-ray to see if you have stones, where they are, how big they are and what their structure is.

Treatment for your kidney stone depends on the size of the stone and where it is.

If the stone is small, it will most likely pass out in your wee, by itself. If it is large, you may need surgery or another treatment to remove it.

Generally, it is better if the stone passes on its own as this avoids the need for surgery.

Treatment to help small stones pass

If you have a small kidney stone, you will not normally need to go to hospital. Your healthcare provider will advise you to drink a lot of water. They may also prescribe:

• pain relief
• medicine such as doxazosin to help the muscles of your ureter relax so the stone can pass through.

Your healthcare provider may ask you to filter or strain your urine to collect any stone you pass so it can be tested to find out what type of stone it is.

Treatment to remove larger stones

If your stones are very large, they can be removed by:

• shock waves (high-energy sound waves) to help break up the stones so you can pass them — the waves are delivered from outside of your body
• surgery, which includes ureteroscopy and percutaneous nephrolithotomy.

After your treatment, you should go to your healthcare provider, after hours or the emergency department if you:

• get severe pain that does not respond to pain relief tablets
• vomit (throw up) or have a fever.

Your wee is affected by what you eat and drink. If you have had kidney stones, these tips will lower your risk of getting them again.

• Drink plenty of fluids. This is the best thing you can do to reduce your risk of kidney stones. Aim for 10 to 12 cups a day. Drinking water is best.
• Eat less salt (sodium). A lot of the salt we eat comes from processed and packaged foods.
• Eat lots of calcium-rich foods, such as milk, cheese and yoghurt, but avoid calcium supplements.
• Eat smaller amounts of animal protein, such as meat, chicken, fish and eggs — 1 to 2 servings a day.