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Kidney stones: definition, symptoms, causes

by Josephine Andrews
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Kidney stones are crystallized components of the urine that form in the kidneys, in the renal pelvis and in the urinary tract. Only when they migrate into the ureter do kidney stones cause pain – severe cramps on the flanks, accompanied by nausea and vomiting (renal colic). The cause is an oversaturation of the urine with stone-forming substances. Find out here what helps with kidney stones.

ICD codes for this disease:

ICD codes are internationally valid codes for medical diagnoses. They can be found, for example, in doctor’s letters or on certificates of incapacity for work.

N20 N13

Brief overview:

  • Symptoms: Pain occurs when kidney stones enter the ureter. Possible symptoms include cramping pain, nausea and sweating.
  • Causes and risk factors: Kidney stones form when certain substances are found in high concentrations in the urine and form crystals.
  • Diagnosis: Various examination methods are available for the diagnosis of kidney stones, including, for example, ultrasound , X -rays or computed tomography (CT).
  • Disease course and prognosis: Kidney stones may recur after successful treatment. However, good stone prophylaxis can significantly reduce the recurrence rate.
  • Prevention: In order to prevent the formation of new kidney stones, increasing the daily amount of fluids and changing lifestyle and diet are recommended.

What are kidney stones?

Kidney stones (kidney stones or nephrolithiasis) are among the urinary stones and are deposits that form from components of the urine. They arise in the tubules of the kidneys, in the renal pelvis and in the urinary tract (e.g. in the ureters or in the bladder). Some are as small as grains of rice, others may fill the entire renal pelvis (foul stones).

Kidney stones are considered a disease of affluence, the development of which is promoted by a protein-rich diet, overeating, obesity (obesity) and a lack of exercise.

Nephrolithiasis occurs on both the right and left sides, depending on the location of the kidneys. The largest kidney stone ever diagnosed weighed 1.36 kilograms.

Composition of kidney stones

Depending on the composition, doctors distinguish between different types of kidney stones:

  • Calcium-containing stones: They make up 70 to 80 percent of all kidney stones. Calcium oxalate stones are by far the most common, followed by calcium phosphate stones.
  • Uric acid stones: They represent about 15 percent of all kidney stones and are also called urate stones.
  • Magnesium ammonium phosphate stones: Their share is around ten percent. Other names are struvite or infection stones.
  • Cystine and xanthine stones: They only make up about two percent of all kidney stones.

The appearance of kidney stones varies depending on the type of stone. Calcium oxalates, for example, are small and have a smooth or spiky surface. Calcium phosphates are slightly larger. These kidney stones can be recognized by their crumbly structure. Cystine stones are kidney stones that are light yellow in color and sometimes get large. Uric acid stones may also become large . Struvite stones are typically antler-shaped.

Kidney stones usually appear between the ages of 20 and 40 and are about twice as common in men as in women.

What symptoms cause kidney stones?

Patients with kidney stones do not experience symptoms in all cases. Pain occurs when kidney stones pass from the kidneys into the ureter and slowly migrate there. These so-called ureteral stones cause symptoms of varying severity depending on their size. Kidney stones (nephrolithiasis) are noticeable in women and men through the following symptoms:

Kidney gravel and very small stones get into the urine and are excreted with the urine – the affected person feels at most a small, stabbing pain when urinating.

Larger kidney stones are more problematic. Acute passage of the stone is accompanied by symptoms such as severe, colicky pain, which increases to almost unbearability within 15 to 30 minutes and radiates to other parts of the body, depending on the location of the stone.

Doctors then speak of renal colic (ureteral colic). It is one of the most intensely felt types of pain in humans and is based on irritation and overstretching of the ureter by the kidney stone that has passed out.

Signs that indicate renal colic and thus kidney stones are:

  • Sudden, severe, stabbing, spasmodic, wavy pain that radiates into the back, the lateral lower abdomen, the groins or into the genital region ( labia , testicles), depending on the location of the kidney stone
  • Nausea, retching and vomiting
  • Bowel movements and flatulence no longer go away (reflex intestinal obstruction).
  • Frequent urination of small amounts of urine (pollakiuria) and an urge to urinate that cannot be suppressed
  • Often blood in the urine due to injuries to the mucous membrane in the urinary tract from the passing stones; the blood is either visible to the naked eye (macrohematuria) or only under the microscope (microhematuria)
  • Motor restlessness
  • Sweating, tendency to collapse
  • Fever, chills and painful urination with additional urinary tract infection

As soon as the passing kidney stone reaches the urinary bladder, the renal colic disappears spontaneously. How quickly this happens depends on the size of the stone. In the case of smaller kidney stones, renal colic sometimes only lasts a few minutes.

Renal colic, which is caused by kidney stones about half a centimeter in size, usually ends after a few hours. In severe cases, when a kidney stone is lodged in the ureter, it may take several days to pass.

Chronic kidney stones: symptoms

Larger kidney stones find it difficult to get into the ureter. They often remain in the renal pelvis and grow into a cast stone, i.e. a kidney stone that fills the entire renal pelvis. The symptoms that occur are often not very pronounced; there is often a dull pressure in the kidney area. In addition, such kidney stones may cause symptoms of urinary congestion and chronic inflammation of the renal pelvis with atrophy of the kidney tissue (shrinking kidneys).

What causes kidney stones?

Kidney stones form when certain substances are present in the urine in too high a concentration. They fall out in initially small crystals, which coalesce over time and grow into kidney stones – kidney gravel forms first, then kidney stones eventually form.

The causes of oversaturation of the urine with stone-forming substances are:

  • Increased excretion of stone-forming substances (such as calcium, phosphate, oxalate, uric acid) and decreased excretion of non-stone-forming substances (magnesium, citrate)
  • Increased urine concentration due to dehydration and dehydration (e.g. through heavy sweating), tropical climate or chronic intestinal diseases
  • Disorders of the calcium metabolism, for example due to an overactive parathyroid gland with increased calcium excretion
  • Disorders of the uric acid metabolism with increased uric acid excretion, which are either based on enzyme defects or are promoted by a diet containing purines (meat), alcohol abuse or the decay of tumor tissue
  • Urine pH less than 5.5 (for uric acid stones) or greater than 7.0 (for phosphate stones)

Risk factors of kidney stone formation

There are a variety of reasons why you get kidney stones. In addition, various factors promote the formation of kidney stones:

  • Foods that remove water from the body and overload the urine with salts promote the formation of kidney stones (e.g. asparagus, rhubarb ).
  • Urinary stasis due to scars , narrowing or malformations in the kidneys or urinary tract
  • Dietary supplements containing calcium and vitamin D
  • Certain medications such as acetazolamide, sulphonamides, triamterene, indinavir, and extremely high doses (over four grams per day) of acetylsalicylic acid (ASA)
  • Occurrence of kidney stones in family members
  • Repeated urinary tract infections
  • Too little fluid intake
  • overweight

Kidney Stones: Investigations and Diagnosis

In many cases, the patient’s medical history already provides evidence of kidney stones. The actual diagnosis is made by the doctor using imaging techniques.

For example, kidney stones can be detected using ultrasound. The ultrasound examination of the urogenital tract is therefore a common method for diagnosing kidney stones, which is often combined with an X-ray examination of the kidneys, ureters and bladder.

Another diagnostic method is excretory urography of the kidneys and urinary tract using X-ray contrast media. Contrast agent administration is not possible in people with a contrast agent allergy or pre-existing kidney function impairment without complex protective measures.

For this reason, spiral CT , a modern form of computed tomography (CT), is increasingly recommended for the diagnosis of kidney stones. This technique does not require contrast media and is used as an alternative to urography.

Depending on the individual case, further examinations are necessary to diagnose kidney stones, such as a cystoscopy with an X-ray of the urinary tract from the bladder (retrograde ureteropyelography) or a scintigraphy (a nuclear medical examination procedure).

During pregnancy, ultrasound imaging is the method of choice for diagnosing kidney stones. X-rays should be avoided in the first trimester if possible.

additional examinations

If kidney disease is suspected, the urine is tested for blood, infection, and chemical changes. Urine is also collected at least once over a 24-hour period in order to calculate the daily excretion of certain substances. The collection of blood values ​​(blood test) helps to assess the kidney function and to identify accompanying inflammation and possible metabolic diseases as the cause of the kidney stones.

People with kidney stones are advised to use a strainer when urinating to catch stones or parts of them when urinating. An examination of the deposits in the laboratory may provide information about the exact cause of the stone formation.

Kidney stones: treatment

You can read everything you need to know about treating kidney stones in the article Kidney Stones – Treatment .

Course of the disease and prognosis

Kidney stones can occur again and again. After successful treatment, 50 percent of patients develop stones again within ten years. However, this high recurrence rate can be significantly reduced by good stone prophylaxis.

How long you are sick in the case of kidney stones varies from person to person. Stones in the ureter that are four millimeters or smaller usually pass spontaneously with conservative treatment with a probability of up to 95 percent within 40 days.

complications

In some cases, kidney stones lead to inflammation of the renal pelvis (pyelonephritis), to blood poisoning due to inflammation of the urinary tract (urosepsis) and to narrowing of the urinary tract. In very serious cases, kidney stones trigger acute kidney failure. Kidney stones are a potentially dangerous condition.

If a kidney stone (ureteral stone) completely blocks the ureter, the urine produced in the affected kidney may no longer drain. Doctors call this urinary retention. The urine collects in the kidneys and with it the toxins filtered out of the blood. These damage the kidney tissue over time.

In addition, urinary retention makes it easier for bacteria to penetrate the urinary tract and settle there – this leads to a urinary tract infection. The combination of urinary retention and infection favors the passage of bacteria from the urinary tract into the bloodstream. The result is urosepsis, i.e. blood poisoning caused by bacteria that have entered the bloodstream from the urogenital tract (urinary and genital tract).

Prevent

In order to prevent the recurrence of urinary stones in adults (recurrence prevention), the following measures are generally recommended:

In its guideline on the diagnosis, therapy and metaphylaxis of urolithiasis, the German Society for Urology (DGU) recommends increasing the daily fluid intake to at least 2.5 to 3 liters and distributing it evenly over 24 hours.

However, for certain risk groups it should be noted that the permissible amount of daily fluid intake may be limited. This applies, for example, to dialysis patients or to patients with an increased risk of heart and blood vessel diseases. For this reason, it is important that patients seek advice from their doctor about the recommended daily amount to drink in their case.

Soft drinks sweetened with sugar (e.g. lemonade, cola, apple juice) are not suitable for preventing the recurrence of kidney stones as they increase the risk of stone formation.

It is also recommended to ensure a varied and balanced diet. This should contain lots of plant-based foods (fruit, vegetables, salad) and grain products, as well as moderate amounts of meat, fish and sausages.

However, oxalate-rich foods (e.g. tomatoes, spinach, rhubarb) may have a favorable effect on the formation of certain kidney stones – so-called calcium oxalate stones.

Physical activity and normalizing body weight are also advised. Less stress may also help prevent kidney stones from forming again.

If it is known what type of kidney stones the patient had, it may be possible to specifically prevent the formation of new kidney stones (e.g. through diet or medication).

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