Kidney Stone Diseases
Prevalence of Kidney Stones
Kidney stone disease is one of the most common problems of the urinary tract system. The number of people experiencing stone problems worldwide is increasing. It is estimated that one in ten people will develop kidney stones during their lifetime. In recent years, the incidence of kidney stones in children has also increased.
Race, gender, and ethnicity can influence the risk of developing kidney stones. White individuals are more prone to developing kidney stones than African Americans or other races. Men experience kidney stones more frequently than women.
What is a Kidney Stone?
Urine contains many dissolved minerals and salts. When some of these minerals and salts are present in high levels in the urine, stones can form.
Kidney stones may start small and not cause any problems at first. However, over time, they can grow large enough to fill the spaces within the kidney. Some stones remain in the kidney and cause no problems.
Sometimes stones pass out of the kidney and move down into the ureter. (The ureter is the tube between the kidney and the bladder.) If the stone reaches the bladder, it can be passed out of the body in the urine. However, if the stone gets stuck in the ureter, it blocks the flow of urine from the kidney, which can be painful.
What Are the Symptoms of Kidney Stones?
Common symptoms of kidney stones include sharp, cramp-like pain in the back and sides. This pain often radiates to the lower abdomen or groin. It usually starts suddenly and comes in waves. The pain may come and go as the body tries to pass the stone.
Other symptoms include:
- A strong urge to urinate.
- More frequent urination or a burning sensation when urinating.
- Dark-coloured or red urine due to blood in the urine. (Sometimes, microscopic levels of blood cells may be present, which are not visible to the naked eye.)
- Nausea and vomiting.
- In men, pain at the tip of the penis or radiating towards the testicles.
What Are Kidney Stones Made Of?
Kidney stones can come in many different types and colours. How your stones are treated depends on the type of stone you have. Preventing new stones from forming also depends on your stone type.
Types of Kidney Stones:
1. Calcium stones (80% of all stones)
Calcium stones are the most common type of stone. There are two types: calcium oxalate and calcium phosphate. Calcium oxalate is more common.
2. Uric acid stones (5–10%)
Uric acid is a by-product of chemical changes that occur in the body. Uric acid crystals do not dissolve well in acidic urine. This leads to the formation of uric acid stones.
Acidic urine can result from the following conditions:
- Being overweight
- Chronic diarrhoea
- Type 2 diabetes (high blood sugar)
- Gout
- A diet rich in animal protein and low in fruit and vegetables
3. Struvite/Infection Stones (10%)
These stones are associated with chronic urinary tract infections (UTIs). Individuals who suffer from recurrent urinary tract infections or who are unable to fully empty their bladder due to neurological conditions are at the highest risk of developing these stones.
4. Cystine Stones (Less than 1% of all stones)
Cystine is an amino acid found in certain foods. Cystinuria (excessive cystine in the urine) is a rare, inherited metabolic disorder. In this condition, the kidneys cannot reabsorb cystine from the urine. High levels of cystine in the urine cause stone formation. Cystine stones usually begin to form during childhood.
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What Causes Kidney Stones?
1. Low Urine Volume
Persistently low urine volume is one of the most important risk factors for kidney stones. Low urine volume can result from fluid loss (dehydration) due to intense exercise, working or living in a hot environment, or not drinking enough fluids.
When urine volume is low, urine becomes concentrated and thick. This causes salts to crystallise and form stones. You can dilute the salts in your urine by increasing your fluid intake, thereby reducing your risk of stone formation.
You can simply adjust this based on the darkness of your urine colour.
Adults prone to stone formation should produce at least 2.5 litres of urine per day. This means consuming an average of approximately 3 litres of fluid per day. The best fluid to use for preventing stones is water.
2. Diet
Your diet affects your risk of developing kidney stones. One of the most common causes of calcium stones is high calcium levels in the urine. Excess calcium in the urine may be related to how the body processes calcium; it is not always related to dietary calcium intake.
Reducing dietary calcium intake is rarely effective in stopping stone formation. Studies have shown that restricting calcium can harm bone health and increase the risk of kidney stones.
Doctors generally do not recommend that patients limit dietary calcium to reduce calcium in the urine. Instead, efforts are made to lower urinary calcium by reducing salt intake.
Excessive salt intake in the diet is a risk factor for calcium stones. This is because excess salt in the urine prevents calcium from being reabsorbed from the urine into the blood. Reducing salt in the diet lowers urinary calcium and reduces the risk of stone formation.
Calcium oxalate stones, the most common type of kidney stones, are associated with foods high in oxalate. Eating foods rich in oxalate can increase the risk of developing these stones.
A diet rich in animal protein (meat, fish, poultry, etc.) makes the body and urine pH more acidic. This facilitates the formation of calcium oxalate and uric acid stones. The breakdown of meat consumed in the body produces uric acid, which increases stone formation.
3. Intestinal Diseases
Certain bowel diseases that cause diarrhoea (e.g. Crohn's disease or ulcerative colitis) or bowel surgery (e.g. gastric bypass) can increase the risk of calcium oxalate stones.
Diarrhoea can cause fluid loss from the body, which reduces urine volume. It can also lead to excessive oxalate absorption from the intestines, causing increased oxalate levels in the urine. Low urine volume and high oxalate levels create conditions conducive to calcium oxalate stone formation.
4. Obesity
Obesity is a risk factor for kidney stone formation. Obesity can lead to stone formation by increasing the acidity of urine.
5. Systemic Diseases
Certain medical conditions can also increase the risk of kidney stones. Abnormal functioning or enlargement of the parathyroid glands, which control calcium metabolism, can lead to increased calcium levels in the blood and urine, which in turn causes stone formation.
Another condition, distal renal tubular acidosis, causes acid to build up in the body, which can increase the risk of calcium phosphate stones.
6. Medications
Certain medications and calcium and vitamin C supplements may increase the risk of stone formation. It is important to inform your doctor about all medications and supplements you are taking.
7. Family History
If any of your family members, such as your parents or siblings, have a history of kidney stones, you are much more likely to develop stones yourself.
How are kidney stones diagnosed?
Silent kidney stones, i.e. stones that do not cause any symptoms, are usually detected using imaging methods such as ultrasound, X-ray or computed tomography.
However, sometimes kidney stones are diagnosed when patients seek medical help due to sudden pain caused by passing a stone.
Various tests may be requested in cases where blood is present in the urine (haematuria) or where pain suddenly occurs in the abdomen or sides. In these cases, ultrasound or CT (computed tomography) scans can clearly diagnose stones. Imaging tests assist the doctor in determining the size and location of the stone.
Blood and Urine Tests
After taking a detailed medical history and performing a physical examination, your healthcare professional may take blood and urine samples. Blood tests can reveal whether there is a medical condition that could cause stones. Urine tests can detect a urinary tract infection, blood in the urine, or the presence of crystals specific to certain types of stones.
If you are at high risk of developing stones again in the future, a 24-hour urine collection test may be performed. This test determines the levels of substances in your urine that cause stones to form. Based on the results, your doctor can help prevent stone formation with proper nutrition and medication.
Imaging Methods
Imaging techniques such as ultrasound, X-ray, and computed tomography (CT) scans are frequently used in the diagnosis of kidney stone patients.
These imaging methods are frequently used both at the initial diagnosis and during follow-ups for stone patients.
Stone Analysis
If you have passed a stone or had it surgically removed, your doctor may request that the stone be analysed. This analysis determines the type of stone. The type of stone helps your doctor plan the most appropriate treatment to prevent future stones.
How is Kidney Stone Treatment Performed?
Kidney stone treatment depends on the following:
- The type of stone
- The location of the stone
- The size of the stone
- The effects the stone has on the kidney
- How long the symptoms have persisted
There are various treatment options available. It is very important to seek expert advice on which treatment is most suitable for you.
Waiting for the stone to pass naturally
In some cases, the stone may pass on its own. Smaller stones, i.e. those less than 5 mm in diameter, are more likely to pass on their own than larger stones. Stones are normally passed from the body in the urine.
The waiting period for the stone to pass on its own is considered safe for up to 2-4 weeks if the pain is tolerable, there are no signs of infection, there is no complete blockage in the kidney, and the stone is small enough to pass. During this period, you should drink plenty of water. If you are in a lot of pain, you may need painkillers.
Medication Treatment
Some medicines can help the stone pass. Some medicines relax the urinary tract, making it easier for the stone to pass. While waiting for the stone to pass, you may also need medicines to reduce pain and nausea.
Shock Wave Lithotripsy (ESWL)
Shock Wave Lithotripsy (SWL) is used to treat stones in the kidney and ureter. Shock waves are directed at the stone using X-rays or ultrasound. When these shock waves repeatedly strike the stone, it usually breaks into small pieces. These small stone fragments are passed out of the body through the urinary tract within a few weeks.
You may be discharged on the same day following ESWL treatment. You can return to your normal daily activities within 2–3 days.
Although ESWL is a widely used and safe method, some side effects may occur. You may have blood in your urine for a few days after treatment. Most stone fragments pass painlessly, but some may become lodged in the urinary tract, causing blockage and pain.
Surgery
If the stone does not pass, the pain is severe, or the stone is affecting kidney function, surgical intervention may be necessary.
If stones cause recurrent urinary tract infections or obstruct urine flow from the kidney, they must be surgically removed. Today, these operations can usually be performed endoscopically, requiring little or no incision. Postoperative pain is minimal and the recovery period is short.
Surgical Treatments Used to Remove Stones from the Kidney and Ureter:
Ureteroscopy (URS)
Ureteroscopy (URS) is used to treat stones in the kidney and ureter. During URS, a very thin telescope called a ureteroscope is advanced through the bladder and then through the ureter to the kidney. Rigid telescopes are used for stones in the lower ureter near the bladder; flexible telescopes (flexible ureterorenoscopy) are used for stones in the upper ureter and kidney.
The ureteroscope allows the surgeon to view the stone without making an incision. General anaesthesia is usually administered during the procedure. Once the stone is located, small stones can be retrieved using a small basket-like device. If the stone is too large, it is broken into smaller pieces using a laser or other stone-breaking instruments.
After the stone has been completely removed, your doctor may place a temporary stent in the ureter. A stent is a thin, rigid plastic tube that keeps the ureter open to allow urine to flow from the kidney to the bladder. It does not require a urinary bag, as it remains inside the body.
Following URS, you may be discharged on the same day or one day after the procedure and can return to normal activities within 2 to 3 days. If your doctor has placed a stent, it will be removed after 2-4 weeks.
Percutaneous Nephrolithotomy (PCNL)
Percutaneous Nephrolithotomy (PCNL) may be an ideal treatment option for large stones in the kidney (2.5 cm and above). General anaesthesia is required for this procedure. PNL is performed through a small incision of approximately half a centimetre in the back or side.
The stone is broken up using an instrument passed through the nephroscope, and the fragments are removed by suction or grasped with special instruments.
A drainage tube may be placed in the kidney to drain urine from the body and stop any bleeding. This tube usually remains in place for a few days or nights. You may need to stay in hospital overnight after the operation.
Other Surgeries
Open surgery, laparoscopic surgery, or robotic surgery are rarely used to remove kidney stones. These methods are only preferred if less invasive procedures fail.
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Why Am I Forming Stones?
Part of preventing stones involves identifying why they form. Your doctor will perform some tests to understand the cause of stone formation. Once the cause is determined, they can provide recommendations to prevent stones from forming again.
Medical and Dietary History
Your doctor will ask questions about your and your family's medical history. For example:
- Have you had more than one kidney stone before?
- Is there anyone in your family with a history of stones?
- Do you have any medical conditions that could increase your risk of developing stones, such as frequent diarrhoea, gout, or diabetes?
Understanding your medical, family and dietary history helps your doctor assess your risk of developing stones again.
How Can I Prevent Kidney Stones?
Once your doctor has determined why you are forming stones, they will offer some recommendations to prevent them. These recommendations may include dietary changes and, if necessary, the use of certain medications. There is no single diet that works for everyone to prevent kidney stones. Each individual is different. However, there are some general dietary changes that may help stop stone formation.
Dietary Recommendations to Prevent Stones
1. Drink Enough Fluids Every Day
If you are not producing enough urine, your doctor may recommend drinking at least 3 litres of fluid per day.
This is one of the best ways to reduce the risk of new stone formation. You may need to drink even more water to replace fluids lost through exercise or sweating in hot weather.
All liquids contribute to your daily fluid intake. However, it is best to choose mostly calorie-free or low-calorie drinks. It is beneficial to limit sugary or alcoholic drinks.
Knowing how much you drink throughout the day helps you understand how much you need to drink to produce 2.5 litres of urine.
2. Reduce Salt in Your Diet
This recommendation is for people with high sodium intake and high urinary calcium or cystine levels. Sodium can increase both urinary calcium and cystine levels.
The following foods are high in salt and should be consumed in limited amounts:
- Cheese (all types)
- Frozen foods and salt-processed meats (salami, sausages, cured meats)
- Canned soups and vegetables
- Bread, baguettes, pastries, and other baked goods
- Crisps. Savoury snacks such as crackers and salted nuts
- Ready-made salad dressings and some breakfast cereals
- Pickles and olives
- Mixed dishes (pizza, lasagne, casserole, etc.)
- Bottled sauces
- Table salt and certain spice blends
3. Consume plenty of fruit and vegetables
It is recommended that everyone who forms kidney stones consume 3-4 portions of fruit and vegetables daily. Fruit and vegetables contain potassium, fibre, magnesium, antioxidants, phytates and citrates, which can help prevent stone formation.
One serving equals one piece of fruit or one cup of raw vegetables. For cooked vegetables, one serving is half a cup. If you are unsure whether you are consuming enough fruit and vegetables, consult your healthcare professional.
4. Consume Foods Low in Oxalate Levels
This is particularly recommended for patients with high oxalate levels in their urine. Consuming calcium-rich foods with meals generally helps control oxalate levels in the urine. This is because calcium intake reduces the amount of oxalate in the body.
However, if this measure is not sufficient, you may be asked to reduce your intake of certain oxalate-rich foods. Almost all plant-based foods contain oxalate, but some contain high amounts. For example:
- Spinach, almonds, figs, corn, red plums, fresh beans, peanuts, blackberries, beetroot, chocolate, currants, okra, cocoa, raspberries, Tomatoes, Tea, Strawberries, Coffee, Chard, Beer, Leeks, Pickles, Parsley, Watercress, Rocket, Aubergines, Dill
It is generally not necessary to completely eliminate these foods; how much to reduce them depends on why your oxalate levels are high.
5. Consume Less Meat
If you are developing cystine or calcium oxalate stones and your urine uric acid levels are high, your doctor may recommend reducing your consumption of animal protein.
Animal proteins such as meat, fish, seafood, poultry, pork, lamb and game can increase acidity in the urine, which facilitates stone formation.
6. Consume Calcium as Needed
If you are taking calcium supplements, ensure you are not taking too much. However, insufficient calcium intake is also risky. Consult your doctor or dietitian to determine whether you need supplements.
Medications Used to Prevent Stones
Dietary changes and increased fluid intake may not be sufficient to prevent stones. In this case, your healthcare professional may prescribe medication. The type of stone and the results of your urine tests will guide the decision on which medication you need.