Brief overview:
- Symptoms: Pain occurs when kidney stones enter the ureter. Possible symptoms include cramp-like pain, nausea and sweating.
- Causes and risk factors: Kidney stones occur when certain substances are present in high concentrations in the urine and form crystals.
- Diagnosis: Various examination methods are available for the diagnosis of kidney stones, including ultrasound, X-ray or computer tomography (CT).
- Course of the disease and prognosis: Kidney stones may recur after successful treatment. However, good stone prophylaxis can significantly reduce the recurrence rate.
What are kidney stones?
Kidney stones (renal gravel or nephrolithiasis) are urinary stones and are deposits that form from components of the urine. They form in the tubules of the kidney, in the renal pelvis and in the urinary tract (for example in the ureters or in the bladder). Some are as small as grains of rice, others may fill the entire renal pelvis (effusion stones).
Kidney stones are considered a disease of affluence, the development of which is promoted by a high-protein diet, overeating, obesity and lack of exercise.
Nephrolithiasis occurs on both the right and left side, depending on the position of the kidneys. The largest kidney stone ever diagnosed is said to have weighed 1.36 kilograms.
Depending on their composition, doctors distinguish between different types of kidney stone:
- Calcium-containing stones: These make up 70 to 80 percent of all kidney stones. By far the most common are calcium oxalate stones, followed by calcium phosphate stones.
- Uric acid stones: These make up around 15 percent of all kidney stones and are also known as urate stones.
- Magnesium ammonium phosphate stones: They account for approximately ten percent. Other names are struvite or infectious stones.
- Cystine and xanthine stones: These make up only around two percent of all kidney stones.
Kidney stones usually occur between the ages of 20 and 40 and are about twice as common in men as in women.
What symptoms do kidney stones cause?
Patients do not always experience symptoms when they have kidney stones. Pain occurs when kidney stones pass from the kidneys into the ureter, where they slowly migrate. These so-called ureteral stones cause varying degrees of discomfort depending on their size. Kidney stones (nephrolithiasis) cause the following symptoms in women and men:
Kidney gravel and very small stones pass into the urine and are excreted with the urine – the person affected feels at most a small, stabbing pain when urinating.
Doctors then speak of renal colic (ureteral colic). It is one of the most intensely felt types of pain in humans and is caused by irritation and overstretching of the ureter by the passing kidney stone.
Signs that indicate renal colic and therefore kidney stones are
- Sudden, sharp, stabbing, cramp-like, wave-like pain which, depending on the location of the kidney stone, radiates to the back, the side of the lower abdomen, the groin or the genital region (labia, testicles)
- Nausea, nausea and vomiting
- Bowel movements and flatulence no longer pass (reflex intestinal obstruction).
- Frequent urination of small amounts of urine (pollakiuria) and urge to urinate that cannot be suppressed
- Motor restlessness
- Sweating, tendency to collapse
- Fever, chills and pain when urinating with additional urinary tract infection
As soon as the outgoing kidney stone reaches the bladder, the renal colic disappears spontaneously. How quickly this happens depends on the size of the stone. With smaller kidney stones, renal colic sometimes lasts only minutes.
Renal colic caused by kidney stones about half a centimeter in size usually ends after a few hours. In severe cases, when a kidney stone becomes lodged in the ureter, it may take several days to pass.
Chronic kidney stones: symptoms
What causes kidney stones?
Kidney stones form when certain substances are present in the urine in too high a concentration. They initially precipitate in small crystals, which coalesce over time and grow into kidney stones – first kidney gravel forms, then kidney stones eventually develop.
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 reduced excretion of non-stone-forming substances (magnesium, citrate)
- Increased urine concentration due to a lack of fluids and dehydration (e.g. due to heavy sweating), tropical climate or chronic intestinal diseases
- Disorders of uric acid metabolism with increased uric acid excretion, which are either due to enzyme defects or are promoted by a purine-rich diet (meat), alcohol abuse or decay of tumor tissue
- Urine with a pH value of less than 5.5 (for uric acid stones) or more than 7.0 (for phosphate stones)
Risk factors for kidney stone formation
There are various reasons why people develop kidney stones. In addition, various factors promote the formation of kidney stones:
- Foods that dehydrate the body and supersaturate the urine with salts promote the formation of kidney stones (e.g. asparagus, rhubarb).
- Urinary congestion due to scars, constrictions or malformations in the kidneys or urinary tract
- Certain medications such as acetalzolamide, 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
- Insufficient fluid intake
- Being overweight
Kidney stones: examinations and diagnosis
In many cases, the patient’s medical history already provides indications of kidney stones. The actual diagnosis is made by the doctor using imaging techniques.
For example, kidney stones can be detected using ultrasound. 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.
This is why spiral CT, a modern form of computer tomography (CT), is increasingly being recommended for the diagnosis of kidney stones. This technique does not require a contrast agent and is used as an alternative to urography.
Depending on the individual case, further examinations may be necessary to diagnose kidney stones, such as cystoscopy with X-ray imaging of the urinary tract from the bladder (retrograde ureteropyelography) or scintigraphy (a nuclear medicine examination procedure).
During pregnancy, ultrasound imaging is the method of choice for diagnosing kidney stones. If possible, an X-ray examination should be avoided in the first trimester.
Additional examinations
People with kidney stones are advised to use a strainer when urinating to catch stones or parts of them during urination. A laboratory examination of the deposits may provide information about the exact cause of the stone formation.
Kidney stones: Treatment
You can read everything you need to know about the treatment of kidney stones in the article Kidney stones – treatment.
Course of the disease and prognosis
Kidney stones may occur again and again. After successful treatment, 50 percent of patients experience a recurrence of stones within ten years. However, this high recurrence rate can be significantly reduced with good stone prophylaxis.
Complications
In some cases, kidney stones lead to inflammation of the renal pelvis (pyelonephritis), blood poisoning due to inflammation of the urinary tract (urosepsis) and constrictions in the urinary tract. In very serious cases, kidney stones can cause acute kidney failure. Kidney stones are therefore a potentially dangerous disease.
If a kidney stone (ureteral stone) completely blocks the ureter, the urine produced in the affected kidney may no longer flow out. Doctors call this urinary retention. The urine collects in the kidney and with it the toxins filtered from the blood. These damage the kidney tissue over time.
Prevention
To prevent the recurrence of urinary stones in adults (recurrence prophylaxis), the following measures are generally recommended:
In its guideline on the diagnosis, treatment and metaphylaxis of urolithiasis, the German Society of Urology (DGU) recommends increasing the daily amount of fluid drunk to at least 2.5 to 3 liters and distributing it evenly over 24 hours.
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 eat a varied and balanced diet. This should contain many plant-based foods (fruit, vegetables, salad) and cereal products as well as meat, fish and sausage products in moderate quantities.
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.
If it is known what type of kidney stones the patient was suffering from, it may be possible to specifically prevent the formation of new kidney stones (for example through diet or medication).