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Kidney stones (nephrolithiasis) are crystalline deposits in the urinary tract or in the renal pelvis. They are usually composed of calcium oxalate, but can also be made of uric acid or calcium phosphate, among other substances. These stones can cause severe pain (renal colic).
In most cases, however, they go unnoticed. Depending on the location, the stones are referred to as kidney stones (nephrolithiasis), ureteral stones (ureterolithiasis) or bladder stones (cystolithiasis). The umbrella term for all of these is urinary stones. Find out more about symptoms, preventive measures and treatment here.
Overview
The smallest crystals are excreted by the kidney every day and are dissolved in the urine. Kidney stones form when certain substances reach a high concentration in the urine and crystallise. If stones pass through the narrow ureter or get stuck in it, this can lead to severe pain, known as renal colic.
The stones can be formed from different crystalline compositions. The following substances, among others, are known to be ‘lithogenic’, i.e. they can lead to the formation of stones:
- Calcium
- Oxalate
- Uric acid
- Phosphate
- Cystine
Kidney stones occur in different sizes: They can grow up to several centimetres in diameter or even fill the entire renal pelvis. The smallest, however, are hardly larger than a pinhead. Smaller stones are often excreted spontaneously in the urine, which is referred to as spontaneous passage.
Certain stones are dissolved with medication. Treatment in the form of surgery is rarely necessary. They occur most frequently between the ages of 30 and 60 and occur more frequently in men than in women. In Switzerland, around 5% of the population will have a kidney stone in their lifetime.
Statistically, around half of all patients should expect a recurrence of nephrolithiasis within ten years. Measures such as an appropriate diet and adequate fluid intake greatly reduce the risk of it recurring.
Causes of nephrolithiasis
In most cases, the reason for the formation of stones can be determined by medical investigations. There are several known risk factors that can lead to the development of urolithiasis.
Family history
There is an increased risk of kidney stones if you or other members of your family have had them.
Diseases
Certain metabolic disorders can also promote kidney stone formation. For example, overactive parathyroid glands can lead to increased release of calcium into the urine.
Diabetics also have an increased risk of developing kidney stones due to the fact that their urine is generally too acidic, which promotes the formation of uric acid stones.
Cystinuria is another illness that can cause kidney stones – even in children. It is hereditary and requires lifelong adaptations to drinking and eating habits.
Low fluid intake
Drinking too little leads to a decrease in the water content and an increase in the concentration of certain substances (e.g. calcium) in the urine. Such substances eventually crystallise and become kidney stones.
Protein-rich diet
Foods such as eggs, meat, fish and seafood, as well as food supplements such as soy shakes, are rich in protein. These cause a significant acid load on the body, which is neutralised by alkaline minerals drawn from the bones and excreted via the kidneys into the urine.
Stone formation is considerably accelerated by the highly acidified urine. People should keep a particularly close eye on their consumption of meat and fish, as these foods may lead to additional uric acid excretion in the urine.
Large amounts of oxalate
Most of the oxalate dissolved in urine comes from the liver, which produces it as the end product of various metabolic pathways. In addition, the consumption of certain foods leads to increased excretion of oxalate. These include foods that stimulate the production of oxalate by the liver and foods that contain a lot of oxalate themselves. Foods that lead to increased excretion of oxalate include:
Foods that cause overproduction of oxalate by the liver
- Sweetened drinks, in particular soft drinks containing fructose
- Gelatine gummy sweets
Foods rich in oxalates
- Chard
- Rhubarb
- Spinach
- Nuts
- Almonds
- Beetroot
If an excessive amount of oxalate is excreted in the urine, that encourages stone formation. This results in one particular subgroup of kidney stones: calcium oxalate stones.
Too much salt
To prevent cardiovascular disease, WHO recommends that people consume less than five grams of salt per day. Adhering to this amount can also help prevent kidney stones. Increased salt intake leads to the excretion of excess calcium in the urine. A high concentration of calcium in the urine can, in turn, lead to the formation of calcium phosphate stones and calcium oxalate stones.
What are the symptoms of kidney stones?
Symptoms include sudden, severe pain in the kidney area that, depending on the position of the stone, can radiate into nearby parts of the body. An increased urge to urinate, discomfort when passing urine or blood in the urine may be other signs of kidney stones. Such complaints should always be examined by a doctor. In rare cases, a tumour may be behind it. Kidney stones can also contribute to the development of pyelitis (inflammation of the renal pelvis).
As long as the stones remain in the kidney, there is usually no discomfort. Often they are so small that they are excreted unnoticed in the urine. Larger stones usually only cause discomfort when they pass through the narrow ureter, or become stuck there.
This is followed by the typical renal colic, which is severe, cramp-like pain in the lumbar region. The pain can also radiate to the groin or the external genitals.
The pain, which usually decreases in intensity within a few minutes, arises because the pressure in the kidney is increased by the backlog of urine. Renal colic is often accompanied by severe nausea, vomiting and fever. Also, as a reaction to the pain, the abdomen may become bloated.
If kidney stones are not treated, this can lead to a narrowing of the ureter. In addition, a disruption in urinary outflow risks causing an infection, which in the worst case can result in life-threatening blood poisoning.
Depending on the severity and duration of the blockage, kidney damage and even loss of kidney function can occur.
Consult a doctor in the following situations:
- The typical pattern of pain occurs
- Kidney stones are not passed spontaneously
- Only a small amount of urine can be passed
- A kidney stone triggers a urinary tract infection
In principle, kidney stones are very treatable. Nevertheless, complications cannot be ruled out in individual cases, especially if the flow of urine is prevented by kidney stones. In this case, a urinary blockage occurs in the affected kidney, and all the toxins in the urine can damage the kidney tissue. In addition, urinary bacteria multiply in the accumulated urine. These factors mean that kidney stones can indirectly lead to serious complications, such as blood poisoning (sepsis), inflammation of the renal pelvis and of the ureter leading from it, acute renal insufficiency (kidney impairment) or even acute kidney failure.
Diagnosis of kidney stones
If a patient is suffering from pain that indicates kidney stones or urinary stones, it is important to confirm whether these are actually the cause, or whether the pain has been triggered by another illness. Pain comparable to kidney stones can also occur, for example, in the case of intestinal obstruction, inflammation of the pancreas, gallstones or appendicitis.
While the functioning of the kidneys can be checked by means of a blood test, a urine test reveals whether a urinary tract infection is present. Finally, procedures such as an ultrasound examination, computed tomography or bladder or ureter endoscopy are carried out for the diagnosis of kidney stones themselves. Kidney stones (urinary stones) are often discovered by chance during an ultrasound examination, which is referred to in medicine as an incidental finding.
Treatment of kidney stones
Patients often wonder whether intervention for kidney stones is absolutely necessary and whether they need to be removed. The answer is no. Smaller stones in particular are often excreted in the urine without any further intervention. If this is not the case, different treatment options may be considered depending on the situation. As a general rule, drinking lots of fluids supports the natural excretion of small stones.
Medication
Uric acid stones can be dissolved (litholysis) with special medication.
Surgical removal
Calcium oxalate stones cannot be dissolved with medication. In this case, the usual choice is to have them surgically removed. As a rule, the surgical removal of kidney stones is carried out endoscopically by means of a cystoscopy and ureteroscopy, often followed by a laser lithotripsy (breaking up the stone with a laser beam).
Shock wave lithotripsy
Breaking up the stones with sound waves is an alternative to the surgery. In a procedure called extracorporeal shock wave lithotripsy (ESWL), the stones are broken up from the outside with targeted sound waves. The resulting smaller pieces are then excreted in the urine.
Prevention
The risk of relapse is high with kidney stones. With the help of preventive measures, those affected can reduce their likelihood of falling ill again. Patients can do the following:
Drink plenty of fluids: Adequate fluid intake, about 2 to 3 litres per day, helps to dilute the urine. Drinking plenty of fluids is particularly important if you lose a lot of fluids due to intense sweating.
Make sure you eat a balanced diet: Foods containing oxalic acid, such as spinach, rhubarb, chard, nuts and almonds, should not be consumed in large quantities. Reducing your consumption of protein-rich foods can also reduce the risk of the formation of uric acid stones.
Take medication as advised by your doctor: Medication can be used to prevent uric acid stones, which changes the pH value of the urine in such a way that the stones shrink or dissolve and can then pass out of the body in the urine.
Get enough exercise: Regular exercise can help prevent kidney stones from becoming established.
Avoid being overweight: When losing weight, care should be taken not to choose a one-sided, strict diet and instead to opt for balanced nutrition, as extreme diets could promote stone formation.
How are kidney stones formed?
Kidney stones are formed when certain substances, such as calcium or uric acid, become concentrated in the urine due to insufficient fluid intake or poor nutrition, forming crystals that combine to form stones.
How do you recognise a kidney stone?
The symptoms caused by kidney stones depend on their location and mobility. In the best case, kidney stones do not cause pain and go unnoticed because they are excreted naturally in the urine.
Larger kidney stones can disrupt the flow of urine and cause further symptoms, such as sudden, severe, wave-like pain that radiates into other areas such as the back, one side of the lower abdomen, or the groin and genital area (kidney colic). In addition, nausea and vomiting, frequent urination with only small amounts of urine being passed, an uncontrollable urge to urinate, pain when urinating, blood in urine, fever and chills may occur.
Can kidney stones recur?
Yes, after first becoming ill with kidney stones there is an increased risk of stones recurring. Common causes include reduced fluid intake, certain eating habits or metabolic disorders. Sufferers can significantly reduce their risk of relapse through an appropriate diet, regular check-ups and adequate fluid intake.
What role does drinking play in kidney stones?
Adequate drinking is an important part of kidney stone treatment and prevention. Drinking enough fluids dilutes the urine and helps the body to excrete small urinary stones via the urinary tract.
When must kidney stones be surgically removed?
Surgical intervention is considered if kidney stones cause severe pain and if stones do not come out of their own accord, block the ureter or interfere with the flow of urine. Surgery may also be necessary in the case of infections, reduced kidney function or larger urinary stones. The aim of the therapy is to avoid complications and relieve the pressure on the urinary tract.
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