Kidney stones are literally ‘stones’ that are situated either in the kidney or in the tube that leads from the kidney to the bladder, known as the ureter.
They can be single or multiple and can range in size from millimetres to several centimetres.
When a stone gets stuck in the ureter or kidney on it's way out of the body, this causes extreme pain felt in the flank (side) or back and is known as renal colic. Kidney stones are three times more common in men affecting approximately 10-20% of men compared with 3-5% of women at some point in their lives.
A common age group to be affected is ages 30 - 50 yrs. Factors that increase the chance of getting kidney stones include:
- people with a family history of kidney stones,
- people of European descent,
- living in hot climates (thought to be due to dehydration).
The kidneys act as the body’s filtering system. By processing our circulating blood, the kidneys absorb the good chemicals and minerals and eliminate the unwanted ones in our urine. If certain chemicals and minerals such as calcium, oxalate, uric acid or phosphate build up in the kidneys or in the urine they can form a stone.
Chemicals and minerals may build up for a variety of reasons including a lack of urine volume (found in people who do not drink enough fluids) or high levels of certain elements in the diet.
- Most stones start out small in size and grow larger over time.
- The stones may stay in the kidney or travel down the ureter into the bladder.
- The majority of stones are composed of calcium oxalate.
- Other types of stones include uric acid, struvite (infected stones) and, rarely, cystine stones.
In many cases, stones can be present without causing any symptoms at all. Stones that stay in the kidney can produce mild to moderate pain in the side but it is the stone that moves from the kidney into the ureter that causes the most severe pain (known as renal colic).
Renal colic is usually sudden, may come and go, and can be excruciating. The pain classically starts in the back and radiates to the groin. If you also develop fevers or cold chills with shakes (rigors), this can be a serious infection and you must see a doctor or after hours clinic straight away!
Kidney stones may also cause all or only a few of the following symptoms:
- blood in the urine
- nausea and vomiting
- a burning sensation when passing urine
- frequent urination (going to the toilet to pass urine more often)
- loss of appetite
- recurrent urinary infections
In many situations, the diagnosis of renal colic or kidney stones can be made just based on the symptoms and history. Sometimes further tests are needed such as one or more of the following:
- If possible, collect the kidney stone. This can be very helpful to find what caused it.
- x-rays (sometimes with injection of dye called an intravenous pyelogram IVP or intravenous urogram IVU)
- a CT (computerised tomography) scan
- renal ultrasound
- urine test looking for blood can also be helpful.
If you continue to form stones, further blood tests and a 24-hour collection of urine will be required. These tests will help to identify any specific risk factors that may be causing your stones to develop. This may lead on to advice from a dietician regarding specific dietary recommendations and, in some circumstances, medications to prevent further stone formation.
Most kidney stones will pass through the urinary tract into the bladder where they will come out in the urine. During this time, you may experience renal colic that will generally be treated with strong painkillers from your family doctor or emergency clinic.
If the pain is controlled and your stone is known to be small, generally the best course of treatment is to wait for several days or weeks for the stone to pass into the bladder.
If, however, the stone is too large to pass or doesn’t pass with time, then treatment is needed. The choice of which type of treatment is best is made by your urologist, depending on many factors such as the size and position of the stone.
The treatment can either be in the form of:
- Ureteroscopy – a small, narrow ‘telescope’ is passed up through the bladder to the stone so that the stone can be removed or broken (sometimes with a laser).
- Lithotripsy– a special machine is used that sends ‘shock waves’ through the body to break up the stone into tiny pieces that will later pass in the urine.
- Percutaneous surgery – a telescope is passed through the skin of the back (and into the kidney) to see and remove the stone. This is reserved for stones that are large and still in the kidney.
- Open surgery – nowadays it is very rare to require a ‘cutting’ operation to remove a stone but it is sometimes the best option.
Approximately 50% of people will only pass one kidney stone in their lives but around 50% will get further kidney stones. The most important thing you can do to prevent further kidney stones forming is to drink lots of fluid.
- Drink at least two to 2.5 litres of fluid each day.
- Drink throughout the day and night if possible.
- The best fluid is water
- You will know if you are drinking enough by the colour of your urine, which should be pale yellow to clear.
- Take the juice of one to two lemons (approximately 100mls daily). This can be diluted with water to drink over the course of the day.
- Reduce salt (sodium) intake by keeping salt in cooking to a minimum and do not add salt to meals.
- Avoid salty foods as much as possible such as:
- Spreads - Marmite, Bovril, Oxo,
- Snacks - salted chips and nuts
- Tinned and packet soups or meats
- Meats - ham, corned beef and smoked fish are high in salt
- Avoid high protein intake as this can increase calcium and oxalate excretion and this increases stone formation.
- Choose small to moderate serves of meat, fish, chicken, eggs, milk and dairy food.
- Make sure you get enough calcium in your diet (low calcium can encourage stone formation)
For adults the recommended daily allowance is approximately 800 milligrams which can be achieved by choosing three to four small to moderate servings of milk and dairy foods (e.g. one serve = a pottle of yoghurt, a glass of milk) per day.
You will be informed by your health professional if further dietary restrictions such as limiting oxalate-containing foods are required.
If you are taking any herbal, vitamin or dietary supplements or antacids, please check with your health professional as these may increase your risk of forming stones.
Kidney stones NHS Choices