The kidney stones , commonly called ” kidney stones ” are hard crystals that form in the kidneys and can cause severe pain. Doctors use the term urolithiasis to describe these crystals, which can also be found in the rest of the urinary system: in the bladder, urethra or ureters (see diagram).
In nearly 90% of cases, urinary stones form inside a kidney. Their size is very variable, ranging from a few millimeters to several centimeters in diameter. Most of them (80%) spontaneously eliminate themselves 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 calculus formed in the kidney, which is in transit to the bladder, can easily obstruct a ureter and thus cause severe pain . This is called renal colic .
Who is affected?
Kidney stones are very common, and their prevalence seems to have increased over the past 30 years. From 5% to 10% of individuals will experience a renal colic crisis during their lifetime. Kidney stones occur more frequently in midlife . They are 2 times more common in men than in women. Some children may also be affected.
More than half of the people who have already had a calculation will have it again in the 10 years following the first crisis. The prevention is very important.
Causes of Kidney stones (renal lithiasis)
The calculations are the result of the crystallization of mineral salts and acids present in too high concentration in the urine. The process is the same as that observed in water containing a lot of mineral salts : beyond a certain concentration, the salts begin to crystallize.
Kidney stones can be a consequence of many factors. Most often, they are due to a lack of dilution of the urine that is to say to a too low consumption of water . An unbalanced diet, too rich in sugar or protein, can also be involved. In many cases, however, there is no specific cause that can explain the formation of stones.
More rarely, an infection, some drugs, a genetic disease (such as cystic fibrosis or hyperoxaluria) or metabolism (such as diabetes) can lead to the formation of urinary stones. Similarly, malformations of the urinary tract can be involved, especially in children.
Types of calculations
The chemical composition of the calculation depends on the cause, but the majority of kidney stones contain calcium . Urine tests and an analysis of the recovered stones make it possible to know their composition.
Calculations based on calcium . They account for about 80% of all kidney stones. They include calcium oxalate (the most common), calcium phosphate, or a mixture of both. They are caused by dehydration, excessive intake of vitamin D, certain diseases and medications, hereditary factors or a diet too rich in oxalate (see Nutrition in the Prevention section).
Struvite (or ammoniaco-magnesium phosphate) calculations . They are related to chronic or repetitive bacterial infections and represent about 10% of cases . Unlike other types of calculations, they are more common in women than in men. Often, they are formed in people who have a bladder catheter.
Uric acid calculations. They represent 5 to 10% of the kidney stones. They are formed due to an unusually high concentration of uric acid in the urine. People with gout or receiving chemotherapy are more likely to suffer from it. They can also be caused by an infection.
Cystine calculations. This form is the rarest. In all cases, their formation is attributable to cystinuria , a genetic abnormality that causes the excretion of an excessive amount of cystine (an amino acid) by the kidneys. This type of calculation can occur from childhood.
The complications are rather rare if the calculations are well cared for. However, it can happen that in addition to an obstruction of a ureter by a calculation, an infection settles. This can lead to a blood infection ( sepsis ) that will require emergency intervention . Another situation that can become serious is when a person with only one kidney has renal colic.
|Important. The health risks associated with kidney stones are great; it is very important to be properly followed by a doctor.|
Symptoms of kidney stones (renal lithiasis)
- A sudden and intense pain in the back (side under the ribs), radiating in the lower abdomen and groin to, and often to sexual area, to a testicle or to the vulva. The pain can last a few minutes or hours. It is not necessarily continuous, but it can become of unsustainable intensity;
- Nausea and vomiting;
- Blood in the urine (not always visible to the naked eye) or cloudy urine;
- Sometimes an urge and frequent urge to urinate;
- In case of concomitant urinary infection , fortunately not systematic, one also feels a burning sensation when urinating, as well as a frequent need to urinate. You can also have fever and chills.
|Many people have kidney stones without even knowing it because they cause no symptoms as such, unless they obstruct a ureter or are associated with an infection. Occasionally, the presence of urolithiasis is discovered during a radiographic examination for another reason.
People at risk of kidney stones (kidney stones)
- People who have had one or more kidney stones
- People who have a family history of kidney stones;
- Men more than women;
- People living in countries with hot and dry climates or working in very hot environments (in commercial kitchens for example), because of the higher risk of dehydration;
- People who have high blood pressure This doubles the risk of kidney stone ;
- 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 (renal lithiasis)
These factors mainly concern people at risk , especially those who have already suffered from kidney stones.
- Bad hydration Drinking little decreases the volume of urine, so concentrates the salts in the urine and increases the risk of crystallization;
- Physical inactivity. The lack of physical activity causes a gradual loss of bone mass, therefore the release of calcium;
- Taking certain medications Taking diuretics (including triamterene) or calcium-based antacids, for example, may increase the risk of developing kidney stones. Sulfonamides and some antivirals like indinavir also increase the risk of gallstones. People at risk should check with 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 calcium, oxalate and uric acid levels in the urine, and decreases citrate levels (a protective factor against stones) . Studies suggest that vegetarianism reduces the risk of kidney stones . However, if the daily quantity of proteins is adequate, whether of animal or plant origin, these do not influence the risk of kidney stones ;
- A diet lacking calcium. Contrary to what one might think, calciumfoodborne (dairy products, canned fish with bones, fruits, green vegetables, legumes, nuts) has a protective effect against kidney stones.
The supplements calcium taken with meals , may have the same effect, but taken alone , they may slightly increase the risk of kidney stones.
Prevention of kidney stones (renal lithiasis)
|Can we prevent?|
|Preventive measures are aimed primarily at people at risk or those who have already had kidney stones . The following approaches may help, but for them to be more effective, it is best to determine the cause of the calculations by submitting to various tests (see Medical Treatments).
|Measures to reduce 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 drinks each day (juice, broths, coffee, etc.). The water is preferred. It is necessary to think to hydrate more when one makes intense physical efforts (the supply of liquid must be then at least 3 liters per day) and during the summer season. People living in hot, dry weather should drink more.
A simple way to find out if you are hydrated enough is to observe the color of the urine : it should be colorless or pale yellow (except for people who have taken vitamin B supplements, which temporarily give the urine a bright yellow color).
Experts from the Mayo Clinic recommend that people at risk or with a history of stones, drink a glass of lemonade home every day. Lemon increases the amount of citrate (a substance that helps prevent stone formation) in the urine. Several studies have confirmed the value of orange juice, tomato or lemon-rich citrate to prevent stone formation.
Some studies have also shown that reducing the consumption of sugary drinks ( sodas ) in some cases, reduces the rate of renal colic.
Warning! It is best to refrain from drinking grapefruit juice. Two epidemiological studies published in the late 1990s linked the daily intake of 240 mL (1 cup) of grapefruit juice to the recurrent formation of kidney stones. However, no test has confirmed these observations. As long as the doubt persists about it, it is better not to consume it, on a regular basis at least.
Reduce ingestion of foods rich in oxalate. People who have already had calcium oxalate-based calculations should limit their consumption of foods that contain a lot of calcium oxalate.
Maintain a good calcium intake. Ingesting calcium-rich foods would have a protective effect on kidney stones. Just make sure to respect the recommended calcium intake. Ask your doctor or consult a dietician if necessary. To find out if you consume enough calcium, use our interactive calculator.
Consume foods rich in potassium . Potassium reduces calcium excretion. The best way to increase your potassium intake is to eat a lot of fruits and vegetables that, for the most part, contain some. Those with the most are potato (with skin), cantaloupe, avocado, lima bean and banana.
Eat enough fiber . The sound is a rich source of insoluble fiber that reduces the absorption of calcium in the intestine, so the calcium level in the urine. People who are experiencing recurrent kidney stones and who are not eating enough fiber may benefit from consuming more. However, the studies conducted to date contradict each other on this subject .
To prevent recurrence of stones, the doctor may prescribe various medications or supplements that vary according to the type of calculation ( thiazide diuretics, allopurinol, potassium citrate, etc.).
Caution with some supplements
Since prolonged high doses of vitamin D can cause kidney stones, it is advisable to consult a doctor before using vitamin D supplements. Vitamin D intake affects blood calcium levels.
There was concern that the long-term use of high doses of vitamin C contributes to the formation of kidney stones because vitamin C is converted into oxalate by the body. According to the authors of a synthesis published in 2005, vitamin C supplementation is safe up to 2,000 mg per day (in divided doses). However, according to a 14-year study of a cohort of more than 45,000 men, taking 1,000 mg or more of vitamin C supplements a day increases the risk of kidney stones slightly. Ask your doctor. It should be noted that the recommended daily nutritional intake of vitamin C is 90 mg for a non-smoking man. The recommended dose to benefit from the antioxidant effect of vitamin C is 500 mg per day.
Medical treatments of kidney stones (renal lithiasis)
The basic salary is based on the results of the various medical tests that the doctor proposes:
- a urine test to check for blood and crystals in the urine and to determine its pH;
- the analysis of a recalculated calculus to determine its type;
- a blood test to check the state of renal function or to detect a metabolic abnormality;
- a computed tomography kidneys, ureters and bladder, which highlights most of the calculations.
Proper hydration is the basic prevention of stones, but only when the pain is less important. Indeed, when the pain is very intense, during the renal colic crisis, do not drink. Because the calculus can be blocked in a ureter, preventing the urine from passing. So, drinking would increase the pressure in the ureter, and therefore the pain.
The majority of calculations (especially if their diameter is less than 7 mm or 80% of calculations) are eliminated on their own within 6 weeks of training , especially if the person consumes a lot of water. During this period, doctors usually recommend drinking about 3 liters of water or other types of drinks a day.
The renal colic is extremely painful. Pain relief may be necessary if they persist for several hours. Nonsteroidal anti-inflammatory drugs, or opioids, can be given intravenously to the hospital when the crisis is very violent.
If the condition is less painful, the person can stay at home under medical supervision. It can relieve pain by taking a paracetamol or acetaminophen (Tylenol, Doliprane) pain reliever until the calculus is removed. The heat also helps to relieve pain (hot baths, hot and wet compresses).
In the case of struvite stones , it is important to treat the urinary tract infection. 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 that has not subsided by analgesics, an internal probe called double probe J or probe JJ must be urgently assembled. It is a small pipe 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 the urine to pass around the calculus, or it raises the calculation in the kidney by pushing it, where it can subsequently be fragmented.
In case of infection, there is urgency: it is necessary to drain urine urgently, so as not to leave these urine infected in the kidney because it would damage or could cause septic shock (sepsis).
If there is no infection, or after the installation of a JJ probe if the calculation is not evacuated, it must be fragmented, that is to say reduced into small pieces or extracted surgically using one of the following techniques:
Ureteroscopy : This is the most frequent intervention thanks to the new technologies, the flexible ureteroscope, the laser and the surgical equipment (pliers or small baskets) allowing to recover the fragments of the calculation or to take it out at once. Ureteroscopy is performed under general anesthesia.
It consists in introducing a pipe equipped with a mini camera (called ureteroscope) by the urethra towards the bladder, until the ureter. The stones are then fragmented or removed intact. The ureter is sometimes damaged either by technique or by calculation if it is irregular and pointed. In this case, the JJ probe can be left in place after the procedure to allow the ureter to heal. The use of analgesics or antispasmodics helps to relieve pain.
Various lifestyle habits as well as other treatments can be implemented to prevent the formation of stones in the future. See the Prevention section.
Extracorporeal shock wave lithotripsy .
It is an external technique that does not require opening the body or entering the body, shock waves diffusing through the skin. During this intervention, ultrasound is directed directly to the calculation. They break it up, and the small pieces can be removed by the urinary system. This intervention can be performed in an outpatient setting, without hospitalization. The risks of the shock wave method is to provoke a hematoma, the shocks being relatively violent, not to succeed in fragmenting it completely, and to require rather long sessions.
The choice of the method depends on the calculations, their location, the type of calculation, its size …
Percutaneous nephrolithotomy . This technique has been a revolution, but it is less and less practiced in favor of flexible uteroscopy. It is used if the calculation is very large or if it is positioned in such a way that it cannot be broken by extracorporeal lithotripsy. The doctor makes an incision in the back and installs in the kidney an observation tube and an instrument called a nephroscope which allows extracting the calculation. If the calculation is too big, it can be split using a laser or electrical energy. Generally, the person who undergoes this procedure stays in the hospital for several days.