Bladder stones will be discussed separately under Bladder Stones.
Stones are formed in the kidney. From the kidney they may gradually grow and then move from the kidney into the ureter (pipe connecting the kidney to the bladder).
Stones affect about three in twenty men and one in twenty women in the UK. They most commonly occur between the ages of 20 and 50, but can occur at any age. Once someone has had a stone there is a 50% chance they will form a further stone within five-ten years.
How do stones form?
The kidneys’ function is to filter the blood and remove unwanted chemicals. These chemicals are passed out in the urine, and some are able to form crystals. The crystals grow to become stones. Crystals, and indeed stones, form more readily when the urine is very concentrated (golden in colour).
Symptoms of stones
Small stones in the kidney may give rise to no symptoms at all. However, kidney stones may grow up to several centimetres in size and give rise most commonly to pain, recurrent urine infections and blood in the urine.
If a kidney stone drops out of the kidney into the ureter pipe this can block the kidney. As urine continues to be made by the kidney, but the pipe is blocked, the kidney is stretched and this causes excruciating pain. Women say this pain can be even worse than the pain of labour. This pain is called renal colic. It is often associated with a feeling of nausea and vomiting and sometimes also with an increasing need to pass urine. Blood may also be seen in the urine and it is something the doctor will check for before making a diagnosis of renal colic. Occasionally a stone may block the ureter in the presence of a urine infection. In these cases a patient may feel hot, sweaty and have the chills or shake. This requires emergency treatment to unblock the kidney to stop the bugs (infection) in the urine escaping into the bloodstream.
The diagnosis of stones is normally made based on the symptoms outlined above. To confirm the presence of a stone, urine is taken to look for blood and to exclude a urine infection. At Urology Partners we will arrange a CT scan, this looks along the length of the urinary system at 1mm intervals so is incredibly accurate at detecting stones. This will identify the site and size of the stone, which dictates how the stone is then treated.
Stones are more likely to form when the urine is concentrated. It is therefore advisable to try and drink plenty of water to avoid stone formation. It is advised that you try and pass 2½ - 3 litres of urine per day. This should keep the urine clear rather than golden.
Even though most stones are made of calcium, patients are not advised to reduce the amount of calcium in their diet. It has been shown that low calcium diets are associated with higher rates of stone formation and therefore dairy products, e.g. milk, cheese and yoghurt, which are rich in calcium, should be taken normally.
A high salt intake may be associated with stone formation. It is therefore advisable not to add salt to your food excessively. A diet low in animal protein (meat) and rich in fibre may also prevent stone formation.
Finally, a chemical called citrate naturally prevents stone formation in the urine. You can increase the amount of citrate in the urine by having a glass of fresh orange juice or freshly squeezed lemon juice each day.
Investigating stone formers
Most patients if they have a single stone episode only require a simple blood test to check the calciumandurate in the blood. However, if the stones have come back, there is more than one stone, there is a family history of stone formation or an underlying medical condition that predisposes to stone formation, then a more extensive investigation called a 24 hour metabolic stone screen will be arranged. This involves collecting urine over a 24 hour period and then the chemicals within the urine can be measured to see if there is an underlying cause for the stone formation.