The Renal lithiasis, 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 with Renal lithiasis ?
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 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.
- 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
- 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.
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.