Kidney stones (renal calculi) are a very common problem. In Australia 8% of people will suffer from a kidney stone at some point during their lives. Men have a 1:10 risk of developing a stone at some point in their lives, and women a 1:35 risk. If you have already had one stone, you have about a 50% chance of forming another stone in the following 5 years. After this time, the risk seems to decline.
Kidney stones (renal calculi) in Adelaide and South Australia are common, and urologists see many patients with this problem. Part of the reason for this is thought to be the hot climate.
The term ‘kidney stones’ is a loose term for stones (calculi) that can occur in the kidney or ureter.
These stones always start to grow in the kidney, and then pass into the collecting system, and may pass down into the ureter.
How are kidney stones diagnosed?
In some people, kidney stones are discovered when they have a sudden episode of severe pain. This happens when a stone moves from the kidney into the ureter, and irritates the lining of this delicate pipe. Sometimes, the stone can cause a partial or complete block to the flow of urine in the ureter, which makes the pain worse. The pain from a kidney stone is often severe enough to cause you to seek medical help straight away. In this setting, a CT scan of the abdomen is done, and this is the best way to diagnose a stone. The CT tells your doctor where the stone is, and its approximate size.
Some individuals who have recurrent urinary tract infections (UTI) may have stones, either caused by the infection, or sometimes actually causing infection. A common investigation for recurrent UTI is an ultrasound, and kidney stones may be detected on the scan.
In others, stones may be discovered by chance on a CT scan or ultrasound scan done for another reason. Stones that are in the kidney (rather than the ureter) often don’t cause pain. However, depending on their size and exact position in the kidney, they may have potential to cause trouble later on.
The different types of kidney stone
Most stones are mixed, meaning there are combinations of chemicals in them.
- Calcium stones and the most common, and of these calcium oxalate is by far the most frequent.
- Struvite stones (infection stones) can be found in patients suffering from repeated urinary tract infections, and usually in women.
- Uric acid stones are found more often in men than women. Patients with gout, or high blood uric acid, diabetes, and patients undergoing chemotherapy are at higher risk of these types of stones, although they can form in people with none of these conditions.
- Cysteine stones are rare, and occur in patients with a hereditary condition called cystinuria.
- Rare stone types are occasionally seen in patients taking certain medications such as acyclovir, indinavir and triamterene (a diuretic).
What has caused my kidney stone?
The likely cause of your kidney stone will be discussed with you. Until a stone is retrieved and sent for analysis, your urologist cannot be absolutely certain of the exact kind, but often there are clues in your history that can give a good idea of the likely cause. Poor drainage of urine from any part of the urinary tract can lead to precipitation of crystals in the urine and stone formation. This is why patients with some abnormalities of the urinary tract, such as PUJ obstruction, may be more likely to form stones. Often, no definite cause for stone formation is found.
Causes of calcium-based stones.
- Low urine output (long term dehydration) – by far the most common cause of kidney stones
- A diet high in red meat and sodium
- Previous bariatric (weight loss) surgery
- Regular high doses of vitamin C
- Excess alcohol consumption
- Inflammatory bowel disease (ulcerative colitis and Crohn’s disease)
- Abnormalities of the urinary tract, for example pelvi-ureteric (PUJ) junction obstruction, medullary sponge kidney, horseshoe kidney.
Causes of uric acid (urate) stones
These can be associated with the following conditions:
- Low urine output (long term dehydration)
- A diet high in red meat
- Excess alcohol consumption
- Low citrate in the urine (hypocitraturia)
- Inflammatory bowel disease (ulcerative colitis and Crohn’s disease)
- Patients with certain malignancies are more prone to uric acid stones
Causes of struvite (infection) stones
- Recurrent urinary tract infections – particularly with bacteria such as Pseudomonas, Proteus, Klebsiella, Staphylococcus or Mycoplasma
- Abnormalities of the urinary tract
- Patients with long standing spinal injury
Causes of cysteine stones
This type of stone forms in patients born with a metabolic problem that causes them to excrete high levels of cysteine and other amino acids in the urine.
How are kidney stones treated?
The type of treatment needed for a kidney or ureteric stone will depend on a number of factors that must be assessed by a urologist. These include the site of the stone (where it is), the number of stones, the size of the stone(s), how long it has been present, your symptoms, any associated infection, and your medical history.
Stones in the ureter
A stone in ureter that is less than 6mm has a reasonable chance of passing on its own, and this can be helped with medications such as indomethacin (an anti-inflammatory) and tamsulosin (a medication that relaxes the muscle in the ureter). If the pain is bearable, and if there is no infection present in the urine, it is often best to try these medicines for about one week, as the stone may pass.
If the pain cannot be controlled, or if you have signs of infection, or if the stone hasn’t passed after giving it some time, you will need a surgical procedure to treat the stone.
Insertion of a JJ ureteric stent
In the presence of infection, the first measure is to have a short general anaesthetic and passage of an internal ureteric stent (a JJ stent). Click this link to take you to information on this procedure Insertion and Removal of Ureteric Stents.
After the infection has settled (typically after one week), you will need the stone removed. This is done with under a general anaesthetic and is called a ureteroscopy and laser (see below).
Ureteroscopy and laser of a ureteric stone
This procedure aims to break the stone in the ureter into very small fragments that can be removed, or allowed to pass on their own. Click this link to take you to information on this procedure Ureteroscopy Semi-Rigid.
Stones in the kidney
The need for treatment for a stone in the kidney depends on many factors, which include size, position, single or multiple stones, your other medical conditions and any problems associated with a stone. Nick will discuss these with you in detail.
Some stones do not need treating, and can simply be watched periodically to make sure they are not causing problems. Small stones often cause no problems. You may have occasional radiology examinations to see if they are growing in size. There may be a small risk that you could develop infection associated with the stone, or sometimes they can fall into the ureter and cause pain and blockage of urine flow from the kidney. If these things happen, the stone will need treating.
Flexible ureteroscopy and laser
This is an operation carried out under general anaesthetic with a long, flexible telescope that passes to the inside of the kidney. The stone can then be lasered into small fragments, which are extracted with the telescope, or allowed to pass on their own. Click this link to take you to information on this procedure Ureterorenoscopy Flexible.
PCNL (percutaneous nephrolithotomy)
For larger stones in the kidney, or for those in places that may be difficult for the telescope to reach and laser effectively, PCNL is an option for treatment. This is a general anaesthetic operation where a small telescope, about the width of an index finger, is passed across the skin and muscle of your back and into the kidney. The stone can then be lasered and extracted.
I’ve had one kidney stone. Am I likely to get another one?
If you have had one stone, on average you have a 10% chance per year of developing another stone over the next five years. This is a 50% chance in 5 years. For some reason, after five years the risk of further stones seems to decline, but some people continue to make stones throughout their lives.
The chance of further kidney stones does depend very much on the underlying cause for your stones, so Nick Brook will talk to you about this in detail.
What can I do to prevent further kidney stones?
Prevention of kidney stones depends on the kind of kidney stone you have had in the past. As mentioned above, the most common kind is a calcium oxalate, and the most common cause is long-term dehydration. Therefore the most effective treatment of stones, for most people, is to significantly increase the amount of fluid you drink. Your urologist may recommend the following steps:
- Increase your fluid intake to 2 litres of fluid per day
- Limit the amount of animal protein (mainly red meat) to 3 portions per week maximum, no more than 150g per portion
- Limit your sodium intake (this reduces the amount of calcium you excrete in your urine)
- You should maintain calcium intake, and if you take calcium supplements for osteoporosis you should keep taking these. However, it is wise to try to keep calcium intake at about 1g/day, unless otherwise instructed by your GP.
In some people who develop stones at an early age, and in people who have (or develop) multiple stones, or have repeat episodes, investigation may be required to look into why these stones are forming. The investigations are simple, and include:
- Blood tests
- Urine tests for acid/alkali (urine pH)
- 24-hour collection of urine
If an abnormality is found in people who form multiple stones, medical treatment can sometimes help. Some of the treatments that can be considered are outlined below, but please remember that individual circumstances vary, and the indications for treatment need to be discussed at length with your urologist.
Calcium oxalate stone prevention - medical treatment
Thiazide diuretics (and a closely related drug called indapamide) can be tried. Studies have shown that the benefit of this kind of treatment is only seen after three years of continuous treatment, and it does not completely prevent further stone formation. There is no benefit in taking drugs that reduce urinary oxalate.
Uric acid stone prevention – medical treatment
Uric acid stone formation can be reduced by making the urine more alkaline (raising the pH value to 6.0-6.5). This requires care, as if the urine pH goes above 7.5, calcium phosphate stones are more likely to form. Treatment with sodium bicarbonate or potassium citrate can achieve this, but potassium citrate (30-80 mEq per day) is the best drug, as sodium bicarbonate may increase calcium levels in urine.
Struvite stone prevention – medical treatment
There is no effective medical treatment for these stones, apart from surgical removal and prevention of future infection in the urine.
Cysteine stone prevention – medical treatment
Medical treatment is difficult, and includes drugs such as penicillamine, alpha-MPG and captopril. Bucillamine is another treatment that has been tried, but is only available in a few countries.
Patients with cysteine stones may be required to drink very large amounts of fluid each day, perhaps 4 litres, so that urine output is greater that 3 litres per day. The urine may also need to be alkalinised to a level beyond pH = 7.5.
The following video is an excellent and comprehensive summary of kidney stones, why they form, and how they are treated:
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