Kidney stones

What are kidney stones?

Kidney stones are hard stones formed from crystalline substances in urine in the kidney. Most of these little crystals leave the body without even being noticed. However, crystals that remain behind can act as crystallisation nuclei and become a kidney stone. Urolithiasis is the medical term for stones in the urinary tract. Men are affected by this five times more frequently than women. The typical age of onset of the disease is between 20 and 40 years. 

Struvite or infection stones are less frequent; they are often caused by a urinary tract infection. Uric acid or cystine stones occur rarely. If a kidney stone is washed into the ureter, it is also called a ureter stone. Gallstones and kidney stones are not connected; they form in different regions of the body. 

Kidney stones: Causes of the disease

The cause of kidney stones often remains unknown. Certain eating habits can lead to them in susceptible people. Urinary tract infections, changes in the kidney and metabolic diseases can also be triggers. 70 per cent of people suffering from the rare hereditary renal tubular acidosis also develop kidney stones. Two other rare hereditary metabolic diseases that can be responsible for kidney stones are cystinuria and hyperoxaluria. 

In the absorptive form of hypercalciuria, the body takes too much calcium from food and releases it via the urine. Due to the high concentration of calcium in the urine, crystals of calcium oxalate and calcium phosphate are formed, which become stones in the urinary tract.

Other causes are hyperuricosuria, uric acid metabolic syndrome, gout, excessive absorption of vitamin D and blockages within the urinary tract. Certain diuretics or calcium-based antacids can promote the formation of kidney stones by increasing the concentration of calcium in urine. Patients who experience chronic inflammation of the intestine, an intestinal bypass or a stoma also have an increased risk. Urinary stones can form in people who have a urinary tract infection. People treated with indinavir because of HIV infection and AIDS are also at an increased risk of forming kidney stones.

Kidney stones: Symptoms of the condition

The first sign of kidney stones is usually a strong sensation of pain. Because the stone is in motion, it causes blockages and irritation, so the pain appears suddenly. It is typically described as a sharp, cramping pain in the back and side of the kidney or lower abdomen. Nausea and vomiting can also occur. The pain can subsequently spread to the groin area. If the stone is too big for a smooth exit, the pain remains because the ureter tries to transport the stone into the bladder using muscle movements. The movement of the stone can also cause discolouration of the urine due to minor bleeding. If the stone moves closer to the bladder, the urge to urinate may increase and a burning sensation may occur during urination. If fever or chills are experienced as accompanying symptoms, a urinary tract infection may also be present.

Laboratory, blood and urine tests to find the cause of the problem

If a patient has already had more than one kidney stone, he will most likely form more stones. To prevent this, it is important to find the cause of stone formation. This is done partly by using laboratory, blood and urine tests. At the same time, the patient’s medical history, profession and eating habits also play a role. An examination of the urine collected over 24 hours is sometimes also performed.