symptom of kidney stones : What are kidney stones

Most people have two kidneys which "clean" the blood. They filter out water and waste products, making urine.
Kidney stones are formed out of crystals found in the urine. In most cases, the crystals are too tiny to be noticed, and pass harmlessly out of the body. However, they can build up inside the kidney and form much larger stones.

If a stone becomes large enough to block the flow of urine out of the kidney, it can cause pressure, pain and infection. If a stone moves out of the kidney with the flow of urine, it can cause severe pain as it moves through the ureters ?the tubes that carry urine from the kidney to the bladder. If a stone gets stuck, an infection can occur. Depending on its size and position, an untreated kidney stone could cause permanent damage to the kidneys.

Depending on where they are located, kidney stones are also known as renal calculi, urinary calculi, urinary tract stone disease, nephrolithiasis, urolithiasis, and ureterolithiasis.

What causes kidney stones?
Kidney stones form when the salts and minerals that are normally found in the urine become out of balance. Different kinds of kidney stones are formed from salts in the urine.

Calcium stones
These are the most common type of kidney stones. They are made of calcium and oxalate, which are chemicals found naturally in certain foods (see "Prevention", below for examples of these foods). A diet with a high content of calcium and oxalate can increase the concentration of these chemicals in the urine and make it more likely for stones to form. Other factors include:

excess vitamin D,
overactive parathyroid glands,
medical conditions such as cancer, some kidney diseases, or a disease called sarcoidosis.
Uric acid stones
Excess amounts of uric acid can be caused by eating a lot of meat. Conditions such as gout and treatments such as chemotherapy can also increase the risk of getting uric acid stones.

Struvite stones (infection stones)
These are caused by too much ammonia in the urine. Ammonia is a chemical produced by the bacteria that cause urinary tract infections. This kind of stone is most often found in women.

Cystine stones
These are caused by a hereditary disorder called cystinuria, which affects about one per cent of men and women.

National Kidney Federation (UK)
0845 6010209
http://www.kidney.org.uk