Kidney stones are hard crystals that form in the kidneys and can cause severe pain. Doctors use the term urolithiasis to refer to these crystals, which can also be found in the rest of the urinary tract: in the bladder, urethra or ureters.
In almost 90% of cases, urinary stones form inside the kidney. Their size varies, ranging from a few millimeters to several centimeters in diameter. Most of them (80%) are eliminated spontaneously by passing through the various ducts of the urinary system and cause few symptoms. However, the ureters, located between the kidneys and the bladder, are very small ducts. A stone formed in the kidney, which is in transit to the bladder, can easily obstruct a ureter and cause severe pain. This is called renal colic.
Who is affected?
Kidney stones are very common, and their prevalence appears to have increased over the past 30 years. Between 5% and 10% of people will experience an attack of renal colic during their lifetime. Kidney stones occur more frequently the 40s. They are twice as common in men than in women. Some children can also be affected.
More than half of people who have already had a kidney stone episode will have it again within 10 years of the first attack. Prevention is therefore very important.
Kidney Stones are the result of crystallization of minerals and acids present in too high a concentration in the urine. The process is the same as that observed in water containing a lot of mineral salts: above a certain concentration, the salts begin to crystallize.
Kidney stones can be the result of a number of factors. Most often, they are due to a lack of dilution of the urine, that is to say to too little water consumption. An unbalanced diet, too rich in sugar or protein, can also be to blame. In many cases, however, there is no specific cause that could explain the formation of stones.
More rarely, infection, certain medications, genetic (such as cystic fibrosis or hyperoxaluria) or metabolic disease (such as diabetes) can lead to the formation of urinary stones. Likewise, urinary tract malformations can be involved, especially in children.
Types of kidney stones
The chemical composition of the stone depends on the cause, but the majority of kidney stones contain calcium. Urine tests and analysis of the stones recovered allow their composition to be determined.
- Calcium-based kidney stones: They account for about 80% of all kidney stones. They include stones made with calcium oxalate (the most common), calcium phosphate or a mixture of the two. They are caused by dehydration, too much vitamin D, certain illnesses and medications, hereditary factors or a diet too rich in oxalate.
- Struvite kidney stones: They are linked to chronic or recurrent bacterial urinary tract infections and represent approximately 10% of cases. Unlike other types of stones, they are more common in women than in men. Often, they form in people who have a bladder catheter.
- Uric acid kidney stones: They represent 5 to 10% of kidney stones. They are formed from an abnormally high concentration of uric acid in the urine. People with gout or who are receiving chemotherapy are more likely to have them. They can also be caused by an infection.
- Cystine kidney stones: This form is the rarest. In all cases, their formation is due to cystinuria, a genetic defect that causes the kidneys to excrete too much cystine (an amino acid). This type of calculus can occur in childhood.
Complications are rather rare if the stones are well cared for. However, it can happen that in addition to an obstruction of a ureter by a stone, an infection sets in. This can lead to a blood infection (sepsis) which will require emergency intervention. Another situation that can become serious is when a person with only one kidney has renal colic.
Symptoms of kidney stones
- Sudden, severe pain in the back (on one side, under the ribs), radiating to the lower abdomen and groin, and often to the sexual area, to a testicle or to the vulva. The pain may last for a few minutes or a few hours. It does not have to be necessarily continuous, but it can become unbearably intense;
- Nausea and vomiting;
- Blood in the urine (not always visible to the naked eye) or cloudy urine;
- Sometimes a pressing and frequent urge to urinate;
- In the event of a concomitant urinary tract infection, fortunately not systematic, one also feels a burning sensation when urinating, as well as a frequent need to urinate. You may also have fever and chills.
Many people have kidney stones without even knowing it, because they don’t cause any symptoms as such unless they have a blocked ureter or are associated with an infection. Sometimes the stones is found on an X-ray for another reason.
People at risk of developing kidney stones
- People who have had one or more kidney stones before;
- People who have a family history of kidney stones;
- Men more than women;
- People living in countries with hot and dry climates or who work in very hot environments (in commercial kitchens for example), due to the higher risk of dehydration;
- People who have high blood pressure. This doubles the risk of kidney stones;
- People with type 2 diabetes;
- People suffering from obesity;
- People with certain metabolic diseases, such as cystinuria (too much cystine in the urine), celiac disease, hyperoxaluria (too much oxalate in the urine), hypercalciuria (too much calcium in the urine) ), renal tubular acidosis (which causes very acidic urine) or hyperparathyroidism;
- People prone to gout attacks;
- People who have recurrent urinary tract infections;
- People with inflammatory bowel disease, such as Crohn’s disease, which increases the absorption of oxalate.
Risk factors of kidney stones
- Poor hydration. Not drinking enough water decreases the volume of urine, therefore concentrates salts in the urine and increases the risk of crystallization;
- Physical inactivity. Lack of physical activity causes a gradual loss of bone mass, hence the release of calcium;
- Taking certain medications. Taking diuretics (including triamterene) or calcium-based antacids, for example, can increase your risk of developing kidney stones. Sulfonamides and some antivirals such as indinavir also increase the risk of lithiasis. People at risk should ask their doctor or pharmacist about their medication;
- A diet very salty or very rich in sugars;
- A diet with an excess of protein. Protein increases the levels of calcium, oxalate and uric acid in the urine, and lowers the level of citrate (a protective factor against kidney stones). Studies suggest that vegetarianism reduces the risk of kidney stones. However, if the daily amount of protein is adequate, whether of animal or vegetable origin, this does not affect the risk of kidney stones;
- A diet deficient in calcium. Contrary to what one might think, dietary calcium (dairy products, canned fish with bones, fruits, green vegetables, legumes, nuts) has a protective effect against kidney stones.
- Calcium supplements, taken with meals, may have the same effect, but taken alone may slightly increase the risk of kidney stones.
How to prevent kidney stones
Preventive measures are aimed primarily at people at risk or those who have already had kidney stones. The following approaches can help, but to be more effective it is best to determine the cause of the stones by undergoing various tests.
Measures to reduce the risk or prevent recurrence
The best way to prevent kidney stones is to drink enough, which means at least 2 liters of water or other types of drink each day (juice, broth, coffee, etc.). However, water is preferred. Remember to hydrate more when making intense physical efforts (the fluid intake should be at least 3 liters per day) and during the summer season. People who live in a hot, dry climate should drink even more.
A simple way to tell if you are hydrating enough is to observe the color of the urine: it should be colorless or pale yellow (except in the case of people who have taken vitamin B supplements, which temporarily give urine a bright yellow color).
Experts recommend that people at risk, or who have had stones in the past, drink a glass of homemade lemonade every day. Lemon increases the amount of citrate (a substance that helps prevent stone formation) in the urine. Several studies have confirmed the benefit of orange, tomato or lemon juice, rich in citrate, in preventing stone formation40.
A few studies have also shown that reducing the consumption of sugary drinks (sodas) can, in some cases, reduce the rate of renal colic.
Proper hydration is the basic prevention of stones, but only when the pain is less severe. Indeed, when the pain is very intense, during the renal colic attack, you should not drink. This is because the stone can get stuck in a ureter, preventing urine from passing. So drinking would increase the pressure in the ureter, and therefore the pain.
Adopt an healthy diet
- Reduce the intake of foods rich in oxalate. People who have had calcium oxalate stones in the past should limit their intake of foods that are high in calcium oxalate. The list of the foods highest in oxalate include: spinach, rhubarb, beets, Swiss chard, peanuts, chocolate, tea, wheat germ, okra, sweet potato and soybean. For more information, ask a dietitian.
- Maintain a good nutritional intake of calcium. Ingestion of foods rich in calcium is believed to have a protective effect on kidney stones. You just have to make sure you respect the recommended daily calcium intake. Check with your doctor or consult a dietitian if necessary.
- Consume foods rich in potassium. Potassium reduces the excretion of calcium. The best way to increase your potassium intake is to eat lots of fruits and vegetables, which most have potassium. The ones with the most are potatoes (with the skin on), cantaloupe, avocado, lima bean and banana.
- Eat enough fiber. Bran is a rich source of insoluble fiber which reduces the absorption of calcium in the intestine, and therefore calcium levels in the urine. People who have recurrent attacks of kidney stones and who do not eat enough fiber may benefit from consuming more. However, studies conducted to date contradict each other on this subject.
To prevent stone recurrence, your doctor may prescribe various medications or supplements that vary depending on the type of stone.
However, be careful with certain supplements. Since taking large doses of vitamin D for long periods of time can cause kidney stones, it is advisable to consult a doctor before taking vitamin D supplements. Vitamin D intake affects the level of calcium in the blood.
There have been concerns that long-term consumption of high doses of vitamin C may contribute to kidney stone formation, as vitamin C is converted into oxalate by the body. According to the authors of a review published in 2005, vitamin C supplementation is safe for up to 2000 mg per day (in divided doses). However, according to a 14-year study in a cohort of over 45,000 men, taking 1,000 mg or more of vitamin C supplements per day slightly increased the risk of kidney stones. Check with your doctor. Note that the recommended daily nutritional intake of vitamin C is 90 mg for a male non-smoker. The recommended dose to benefit from the antioxidant effect of vitamin C is 500 mg per day.
Treatment of kidney stones
The basic treatment is established according to the results of the various medical tests that the doctor offers:
- Urinalysis to check for blood and crystals in the urine, and to determine its pH;
- Analysis of a recovered stone to determine its type;
- A blood test to check the state of kidney function or to detect a metabolic abnormality;
- A CT scan of the kidneys, ureters, and bladder, which shows most stones.
The majority of stones (especially if their diameter is less than 7 mm or 80% of stones) are eliminated on their own within 6 weeks of their formation, especially if the person consumes a lot of water. During this time, doctors usually recommend drinking about 3 liters of water or other types of drink per day.
Renal colic is extremely painful. Pain relief may be necessary if pain persists for several hours. Nonsteroidal anti-inflammatory drugs, or opioids, may be given intravenously in clinical setting when the attack is very severe.
If the condition is less painful, the person can stay home under medical supervision. He or she can relieve her pain by taking a pain reliever such as paracetamol or acetaminophen (Tylenol, Doliprane), until the stone has cleared. Heat also helps relieve pain (hot baths, hot and wet compresses).
It is important to treat the urinary tract infection if you have struvite stones. It is also necessary to discover and eliminate as much as possible the factors that predispose to infections.
In the event of an infectious sign or pain not calmed by analgesics, an internal probe called a double J probe is used as a matter of urgency. This is a small tube that the doctor enters through the urethra, passes into the bladder, and then places it between the bladder and the kidney in each of the ureters. This JJ probe allows urine to pass around the stone, or it pushes the stone up into the kidney, where it can later be fragmented.
In case of infection, it is necessary to drain the urine urgently, so as not to leave these infected urine in the kidney because this would damage it or could cause septic shock (septicemia).
After the placement of a JJ probe, if the stone is not evacuated, it will have to be fragmented, i.e. reduced into small pieces or extracted surgically using one of the following techniques:
This is the most frequent intervention thanks to new technologies. Ureteroscopy is performed under general anesthesia. It involves inserting a tube with a mini camera (called a ureteroscope) through the urethra to the bladder, up to the ureter. The stones are then fragmented using a laser or taken intact. The ureter is sometimes injured either by the equipment or by the stone if it is irregular and sharp. In this case, the JJ catheter can be left in place after the procedure to allow the ureter to heal. The use of analgesics or antispasmodics helps relieve pain.
Extracorporeal shock wave lithotripsy.
It is an external technique that does not require opening the body or entering inside our body, the shock waves diffusing through the skin. During this procedure, ultrasound is directed directly to the stone. It break it up, and the small pieces can be eliminated through the urinary system. This intervention can be performed on an outpatient basis, so without hospitalization. The risks of the shock wave method include a hematoma (localized bleeding outside of blood vessels), the shocks being relatively violent, failure to fragment the stone entirely, and sometimes long sessions.
The choice of method depends on the kidney stones, their location, their type and their size, etc.
This technique was a revolution when it first appeared, but it is less and less practiced today in favor of the flexible uteroscopy. It is used if the stone is very large or if it is positioned in such a way that it cannot be fragmented by extracorporeal lithotripsy. The doctor makes an incision in the back and places an observation tube and an instrument called a nephroscope in the kidney to remove the stone. If the stone is too large, it can be split using a laser or electric power. Usually, the person having this procedure stays in the hospital for several days.
Kidney stone disease is mostly a disease of industrialized countries. The worse we eat, the more we are at risk of developing kidney stones. So it is a disease of civilization. You should never neglect a stone, because it can get painful, get bigger, but worse still, damage or destroy the kidney. Kidney stones were the number one cause of kidney destruction at the turn of the century. So don’t let it get bigger, but treat it, even if it doesn’t hurt.
The treatment of kidney stones is usually done with anti-inflammatory drugs and analgesics. Some situations are urgent and require very quick actions. Otherwise, you risk damaging your kidneys or finding yourself in a very serious situation that could jeopardize your life.
Above all, please talk to your doctor.
Born in London, England and raised in Orlando, FL, Elena graduated from the University of Central Florida with a bachelors’ degree in Health Sciences. She later received her masters’ in Creative Writing from Drexel University. She writes part-time for the Scientific Origin and focuses mostly on health related issues.