Last updated on 20 December 2021
What are kidney stones?
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.
Types of kidney stones
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.
Uric acid stones
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.
What are the causes of kidney stones
There are various reasons why minerals in our urine may crystallise and join together, forming stones. Some factors that increase your risk of developing kidney stones are:
Lack of water
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.
Family and personal history of 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.
Certain medical conditions
Having certain medical conditions, such as inflammatory bowel disease, type 2 diabetes, gout, and chronic diarrhoea can increase your risk of developing kidney stones.
What are the risk factors for kidney stones?
- Family history. You are more likely to develop kidney stones if someone in your family has it. You are also at increased risk of developing new kidney stones if you have already had one or more kidney stones.
- Dehydration. If you don’t drink enough water daily, especially if you live in warm, dry climates or if you sweat a lot, you may be at higher risk than others for developing kidney stones.
- Obesity. Individuals with a high body mass index (BMI) and large waist size are more likely to develop kidney stones than those of a normal weight. This is because people who are overweight tend to consume more salt and animal fat in their diet which increases the likelihood of stone formation.
- Certain diets. Diets that are high in protein, salt and sugar may increase your risk of kidney stones.
- Digestive diseases. Inflammatory bowel syndrome (IBS) or chronic diarrhoea can cause changes in the digestive process that affect the absorption of calcium and water. This can increase the amounts of substances in your urine that can form into kidney stones.
- Surgery. Having a gastric bypass surgery can also affect the absorption of calcium and water by your digestive system, leading to increased amounts of stone-forming substances in your urine.
- Medical conditions. Certain conditions such as, renal tubular acidosis, cystinuria, hyperparathyroidism and repeated urinary tract infections (UTI) can increase the risk of kidney stones.
- Medications & supplementation. Vitamin C, dietary supplements, laxatives when used excessively, calcium-based antacids and certain medications for migraines and depression are among medications and supplements that can increase your risk of kidney stones.
What are the symptoms of kidney stones?
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:
- Severe pain in the back, abdomen, or side. Kidney stone pain typically comes and goes, and fluctuates in intensity. The pain may start in the upper back and move down towards the abdomen and groin.
- Pain when passing urine
- Blood in urine. In such cases, your urine may appear pink, red, or brown.
- Nausea and vomiting
- Fevers and chills in the event of an infection.
Foods that prevent kidney stones
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.
- Fluids. Increasing your intake of fluids, especially water, is one of the best ways to prevent and treat kidney stones.
- Citrus foods. Citrus foods such as lemons, lime, apple cider vinegar and oranges contain citric acid, which may help prevent new kidney stone formation and enlargement of existing stones. An easy way to increase your intake of citric acid is by adding citrus fruit juices to your water.
- Calcium. As calcium stones are one of the most common types of kidney stones, you may think that you should avoid calcium to reduce the chances of getting kidney stones.
However, the opposite is true. Eating calcium is important as it combines with oxalate in our stomach and intestines before it reaches the kidney. This allows oxalate to leave our body without forming kidney stones.
- Wheatgrass. Wheatgrass contains compounds that increase urine flow, which allows stones to pass more easily and reduces your risk of developing kidney stones.
Wheatgrass is also high in nutrients and antioxidants that can help cleanse our urinary tract and kidneys.
You can start taking wheatgrass by up to a cup of fresh wheatgrass juice a day. Alternatively, you can take wheatgrass supplements which are widely available.
How are kidney stones diagnosed?
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.
Analysis of passed stones
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.
How are kidney stones treated?
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 (ESWL)
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.
When should you seek medical attention?
You are advised to visit the Accident and Emergency (A&E) department if you are experiencing the following symptoms related to your kidney stone:
- Fever, with a temperature higher than 39ºC
- Persistent nausea and vomiting
- Severe pain
Find out more about whether your symptoms warrant a trip to the A&E.
Article reviewed by Dr Shirley Bang, urologist at Parkway East Hospital
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