Kidney stones (nephroliths, renal calculi) are formed when substances dissolved in the urine precipitate in the kidney and form crystals as well as smaller and larger deposits. Many small kidney stones are known as renal gravel. These formations can dissolve and be excreted with the urine via the ureter. However, if they are larger, they can become lodged in the ureter as ureteral calculi and cause renal colic. Kidney stone disease is one of the most common kidney diseases and is also known as nephrolithiasis. Kidney stones can be differentiated according to their external shape and chemical composition. Most commonly, they consist of calcium oxalate, a calcium salt.
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If the concentration of salts in the urine increases, the dissolved substances precipitate. This can already be the case as a result of water loss due to heavy sweating or chronic intestinal diseases or due to not drinking enough. All circumstances that increase the concentration of salts in the urine are considered possible causes. These include, for example, urinary outflow obstructions (e.g. due to kidney malformations), but also diet. Excessive meat and sausage consumption and foods with an increased oxalic acid content (such as spinach and chocolate) are considered risk factors.
If illness leads to an increased release of calcium from the bones, the risk of stones in the kidneys is also increased. Gender also plays a certain role. Men suffer from nephrolithiasis about three times as often as women. In addition, diseases such as gout, repeated urinary tract infections and parathyroid disorders are also held responsible for stones in the kidneys.
Small stones in the kidneys do not usually cause any symptoms. However, if larger stones block the outflow of urine, they can cause pain in the kidneys. Renal colic occurs when the stone enters the ureter and gets stuck there and is only excreted slowly. Renal colic is characterized by the following symptoms, among others: severe pain in the kidney area, nausea and vomiting, blood in the urine, bloated abdomen and fever. The pain of renal colic is one of the most intensely felt pain conditions. The pain subsides when the stones reach the bladder; it can last a few minutes with smaller stones, but can last several days with large, lodged stones. These symptoms can also occur in a milder form during urination.
The medical history and the description of the symptoms often provide the first indications of possible kidney stones. The doctor will try to rule out other illnesses by carrying out physical, blood and urine tests, as well as finding further evidence of stones in the kidneys. Imaging procedures(ultrasound examination, excretory urography, magnetic resonance imaging, computer tomography) can be used to detect stones and any urinary retention.
Most kidney stones are excreted in the urine on their own, so that no treatment is necessary in these cases. Excretion can be supported by conservative or active measures. These include
- Conservative treatment of kidney stones includes pain management, application of heat, exercise and plenty of fluids. If renal colic occurs, treatment must be discontinued and the kidney stone actively removed.
- Drug treatment (litholysis) involves administering substances that dissolve the stones.
- In extracorporeal shock wave lithotripsy (ESWL), the stones are broken up by pressure waves (shock waves). The debris is then excreted spontaneously with the urine.
- In percutaneous nephrolitholapaxy (PCNL), a hollow needle is advanced through the skin to the kidney. The kidney stone is then crushed and removed using a special instrument.
- Surgical stone removalis used to removeureteral stones that are stuck. A catheter is inserted via the urethra and urinary bladder into the ureter. Instruments are then inserted via the catheter to break up the stone or, in rare cases, to pull it out.
The following measures can effectively prevent the formation of new kidney stones:
- Adequate fluid intake (about 2 to 3 liters per day)
- Additional fluid intake in case of excessive water loss through sweating and chronic intestinal diseases
- Low salt diet
- Change your diet: reduce consumption of animal protein and foods high in oxalic acid and purines
- Avoidance of obesity
- Regular physical activity (sport)
Kidney stones are usually treated by specialists in urology. Further imaging examinations are carried out by radiologists. Specialist clinics for kidney stones are usually urology clinics.
