Kidney stones are hard deposits of salt and minerals that form within the kidney or urinary tract. Depending on where the stone is located, it can be termed a kidney stone, ureteric stone, or bladder stone. Calcium stones in the form of calcium oxalate are the most common type of stone. While these substances usually dissolve in urine, some factors, such as certain medical conditions and nutrition, can cause their concentration in urine to rise, forming crystals.
Kidney stones can cause severe pain. Left untreated, they can lead to serious complications such as kidney damage or kidney infection.
Kidney stones can affect people of any age, even children. However, men aged 20 – 40 years old are at greater risk of being affected.
There are different types of kidney stones, depending on the cause. The type of kidney stone will help to determine how best to prevent them from happening again. Types of kidney stones include:
These are the most common type of kidney stones, normally in the form of calcium oxalate. Oxalate is a substance produced by the liver and certain foods such as nuts and chocolate are also high in oxalate content. Other factors that can increase the concentration of calcium or oxalate in urine are high doses of vitamin D, certain kinds of metabolic disorders and having had intestinal bypass surgery.
Calcium stones can also appear in the form of calcium phosphate, which occurs more commonly in those with metabolic conditions and is also associated with certain medications used to treat migraines and seizures.
Struvite stones grow quickly in response to a urinary tract infection. They may present with few symptoms even though they can grow to a large size.
These types of stones are more likely to form as a result of a high-protein diet or loss of fluids caused by chronic diarrhoea. Those with diabetes, metabolic syndrome and certain genetic factors may also increase your risk.
Cystine stones are found in those with a hereditary disorder known as cystinuria, which causes the kidneys to excrete excessive amounts of a certain amino acid.
Drinking enough water is crucial to preventing kidney stones. Drinking more water allows us to produce more urine, reducing the chance of kidney stones forming due to undissolved minerals in our urine. Aim to drink at least 8 – 10 glasses of water each day.
A common type of kidney stone is the calcium oxalate stone, which can develop from having too much oxalate in our urine. Oxalate is a natural compound found in food. High-oxalate foods include spinach, coffee, chocolate, sweet potatoes and soy products.
A high-sodium diet can also increase your risk of getting kidney stones. Having too much salt in your urine can prevent calcium from being reabsorbed into our blood, resulting in high urine calcium. This can lead to kidney stones. High-sodium foods include frozen meals, canned vegetables and soups, deli meats and sauces.
Researchers have found that being obese, having a higher Body Mass Index (BMI) and larger waist size increases your risk of developing kidney stones.
You are more likely to develop kidney stones if someone in your family has had kidney stones. Having a personal history also increases your risk of developing kidney stones again.
Certain medications can cause kidney stones, such as calcium-based antacids, steroids, and anti-seizure drugs.
Smaller kidney stones that remain in the kidney do not usually cause any symptoms. Symptoms are likely to appear only when the stone moves from the kidney tract down the ureters (tubes that carry urine from the kidney to the bladder).
Symptoms of kidney stones include:
Some kidney or ureteric stones are small enough to be passed out through your urine, and can be treated and prevented at home by taking plenty of water, eating the right foods, and taking painkillers (as prescribed).
These foods are natural remedies that can be helpful in increasing your chances of passing kidney stones, and preventing their development. It is important to first consult your doctor on the suitability of these remedies, especially if you have pre-existing medical conditions or are taking medication.
To confirm if your symptoms are indeed caused by kidney stones, several tests may be recommended.
Blood tests can show if there is too much calcium or uric acid in the blood, or indicate some other sign of kidney problems.
A urine test will collect urine for 24 – 48 hours and analyse if it has too many minerals that may lead to the formation of kidney stones, or too few of the substances that help to inhibit the formation of stones.
Ultrasound allows doctors to see if there are kidney stones presence, and computerised tomography (CT) scans can reveal stones in the kidneys or urinary tract, even small ones that regular X-rays may miss.
You may be asked to urinate through a strainer to catch any stones that may pass. These are sent to for lab analysis to determine its type, allowing your doctor to determine what's causing the stones and how best to prevent them.
Kidney stone treatment varies depending on the size, type and location of your kidney stone, and some small kidney stones do not necessarily involve surgery. Upon assessment, your doctor will be able to suggest a suitable treatment for you.
If your kidney stones are too large to be passed naturally, your doctor may suggest removing the stones through procedures such as Extracorporeal Shock Wave Lithotripsy, Ureterorenoscopy or Percutaneous Nephrolithotripsy.
Extracorporeal shock wave lithotripsy is a common, non-invasive treatment for kidney stones. In this procedure, high-energy shockwaves are directed at the kidney stones from outside the body, which help to break the stones into fragments that are small enough to be passed out in urine.
A ureteroscopy is performed when kidney stones are present in the ureter. In this procedure, a thin scope is inserted into the bladder and ureter to break up small stones using shock wave lithotripsy. It is less effective for large stones, but it may be more suitable for certain patients such as pregnant women, those who are morbidly obese and those who are unable to stop taking blood-thinning medication.
Percutaneous nephrolithotripsy or nephrolithotomy may be advised for stones that are larger than 2cm, stones that are irregularly shaped or stones that are insufficiently broken up in ESWL. A surgeon will make a small incision in the patient's back to access the kidney through which a nephroscope and small instruments can be inserted. In a nephrolithotomy, the stone can be removed through the tube while a nephrolithotripsy means the stone must be broken up using high frequency sound waves before it can be removed.
Find out more about whether your symptoms warrant a trip to the A&E.