Kidney stones (nephroliths, renal calculi) form when substances dissolved in the urine precipitate in the kidney, forming crystals and deposits of varying sizes. Many small kidney stones are referred to as kidney grit. These formations can break loose and be excreted with the urine through the ureter. However, if they are larger, they can become lodged in the ureter as a ureteral stone and trigger renal colic. Kidney stone disease is one of the most common kidney disorders; it is also known as nephrolithiasis. Kidney stones can be classified based on 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 out. This can occur as a result of fluid loss due to heavy sweating or chronic intestinal disorders, or from not drinking enough fluids. Thus, any circumstances that increase the concentration of salts in the urine are considered possible causes. These include, for example, obstructions to urine flow (e.g., due to kidney malformations), as well as diet. Excessive consumption of meat and processed meats, as well as foods with a high oxalic acid content (such as spinach and chocolate), are considered risk factors.
If illness leads to increased calcium release from the bones, the risk of kidney stones is also elevated. Gender also plays a certain role. Men are about three times more likely to suffer from nephrolithiasis than women. In addition, conditions such as gout, recurrent urinary tract infections, and parathyroid disorders are also implicated in the development of kidney stones.
Small kidney stones usually do not cause any symptoms. However, if larger stones block the flow of urine, they can trigger pain in the kidney. Renal colic occurs when the stone enters the ureter, becomes lodged there, and is excreted only slowly. Renal colic is characterized by the following symptoms, among others: severe pain in the kidney area, nausea and vomiting, blood in the urine, a bloated abdomen, and fever. The pain associated with renal colic is among the most intense types of pain a person can experience. The pain subsides once the stones reach the bladder; with smaller stones, this may take only a few minutes, but with large stones that become lodged, it can last several days. These symptoms may also occur in a milder form during urination.
Often, the patient’s medical history and description of symptoms provide the first clues to possible kidney stones. The doctor uses physical examinations as well as blood and urine tests to rule out other diseases on the one hand, and to find further evidence of stones in the kidney on the other. Imaging techniques (ultrasound, excretory urogram, magnetic resonance imaging, computed tomography) can detect stones and any urinary obstruction that may be present.
Most kidney stones are passed naturally in the urine, so no treatment is necessary in these cases. The passage of stones can be aided by conservative or active measures. These include:
- Conservative treatment of kidney stones includes pain management, heat therapy, physical activity, and drinking plenty of fluids. If renal colic occurs, conservative treatment must be discontinued and the kidney stone actively removed.
- In drug therapy (litholysis), substances are administered to dissolve the stones.
- In extracorporeal shock wave lithotripsy (ESWL), the stones are碎ed into smaller pieces using pressure waves (shock waves). The fragments are then spontaneously excreted in the urine.
- In percutaneous nephrolitholapaxy (PCNL), a hollow needle is advanced through the skin to the kidney. The kidney stone is then fragmented and removed using a special instrument.
- Surgical stone removal is used for stones lodged in the ureter. In this procedure, a catheter is advanced through the urethra and bladder into the ureter. Instruments are then inserted through the catheter to break up or, in rare cases, extract the stone.
The following measures can effectively prevent the formation of new kidney stones:
- Adequate fluid intake (about 2 to 3 liters per day)
- Increased fluid intake in cases of excessive water loss due to sweating and in cases of chronic intestinal diseases
- A low-salt diet
- Dietary changes: Reduce consumption of animal protein as well as foods high in oxalic acid and purines
- Avoiding excess weight
- Regular physical activity (exercise)
Kidney stones are typically treated by urologists. Further imaging tests are performed by radiologists. Specialized clinics for kidney stones are usually urology clinics.
