If you have one kidney stone, you are likely to have another. So careful assessment and the right treatment are essential to lower your risk.
Kidney or renal stones known as nephrolithiasis, cause severe pain and may ultimately lead to chronic kidney disease (CKD). They are also very common: around one in every eleven people will develop a kidney stone during their lifetime. Doctors are also diagnosing kidney stones more frequently, especially in women.
What causes kidney stones?
Kidney stones can develop in one or both kidneys and come in a range of shapes and sizes. Some are as small as a grain of sand, while a few may grow to the size of a golf ball.
“Stones that develop in your kidney are a bit like stalactites and stalagmites: they form over time through a build-up of mineral crystals. The most common type is made from calcium salts (like stalactites and stalagmites); other stones result from the breakdown of uric acid found in some foods or, more rarely, the build-up of a phosphate mineral called struvite following frequent urinary tract infections,” explains Dr Shabbir Moochhala. Shabbir is Consultant Nephrologist at the Royal Free Hospital, London, and runs a specialist renal stone clinic.
Factors that increase the likelihood of kidney stones are listed in Table 1. Lifestyle plays a part, especially not drinking enough fluid to dilute your urine, but not everyone with these risk factors develops a stone. Some people are more likely to develop kidney stones because of a medical condition, or their genetic inheritance.
“The good news for kidney patients is that you do not have a higher risk of kidney stones simply because you have problems with your kidneys. Stones after a kidney transplant are very rare, but if you do get one, it may be due to the anatomy of the transplant, or you might already have had an underlying predisposition before you had the transplant,” says Shabbir.
Factors increasing your risk of kidney stones
- Not drinking enough fluid to dilute your urine
- Family history of kidney stones
- Previous kidney stone(s)
- Frequent urinary tract infections
- Some medical conditions affecting the kidney; e.g. sarcoidosis or Dent disease
- Conditions that affect how minerals are absorbed by the body; e.g. Crohn’s disease and after gastric bypass surgery
- Lifestyle: e.g. diet high in protein and sodium, but low in calcium; sedentary lifestyle; obesity
- Certain medicines; e.g. antacids, diuretics
How do I know if I have kidney stones?
If a stone stays in the kidney, you are unlikely to have any symptoms, and you only find out about the stone when you have an X-ray or scan for another condition. The exception is if the stone continues to grow within the kidney, when it may cause infection (pyelonephritis) and eventually damage the kidney.
You usually start to have symptoms when the stone moves from the kidney into the ureter, the tube that takes urine from the kidney to the bladder. Symptoms include blood in your urine, urinary tract infections, and aching in your loin or flank. You may sometimes see tiny pieces of stone (gravel) in your urine.
As the stone moves down your ureter, you may get a severe pain called renal or ureteric colic. Many people say that it is the worst pain they have ever had, and it is often accompanied by nausea and vomiting. The pain usually starts along the side of your body in your loin and may spread down to your groin or genitals as the stone moves along the ureter.
If you pass a stone, save it to show your doctor
Shabbir adds: “Kidney stones are rare in a transplanted kidney but they are a cause for concern, because you will not feel pain as the stone moves down your ureter. When we remove a kidney from the donor, we take the donor’s ureter along with the kidney’s blood vessels (the renal vein and artery). This means that the surgeon cuts the nerves to the donor’s ureter. The surgeon can sew the kidney’s blood vessels to your artery and vein, but cannot connect the ureter’s nerves to your body. So transplant recipients with a stone are often diagnosed late when they present with rising creatinine and signs of infection.”
How are kidney stones treated?
Renal colic is a medical emergency, so you must go to A&E. In hospital, the first-choice investigation is an urgent (i.e. within 24 hours) computed tomography scan of the kidneys, ureters and bladder (CT KUB). This type of scan does not use contrast, so you should have no worries if you have CKD.
If you cannot have a CT KUB, the alternative is an ultrasound scan, which is also used for monitoring kidney stones to avoid repeated doses of CT radiation. A magnetic resonance imaging (MRI) scan is an option if ultrasound is not possible.
Pain relief is a priority when you have a kidney stone. A non-steroidal anti-inflammatory drug (NSAID) is the first-choice treatment, and is often given intravenously if you have renal colic.
“A short course of an NSAID is a good choice for pain relief if you have normal kidney function, but it is not a sensible long-term option if you have CKD. If you cannot take an NSAID, the alternative is paracetamol or possibly an opioid drug if the pain is very severe,” says Shabbir.
Treatment depends on the site and size of your stone. Small stones that are not causing symptoms can be managed conservatively with ‘watchful waiting’—i.e. drinking lots of water to try to flush out the stone from your body. You may also be given alpha-blocker tablets to relax the ureter and help the stone to pass by itself.
“If you pass a stone, save it to show your doctor. Analysis of the stone can be the single most important piece of information we need to tell you what caused your stone and how we can stop it happening again,” explains Shabbir.
Conventional open surgery is rarely needed for kidney stones. Small stones are treated with extracorporeal shock wave lithotripsy (ESWL), which uses X-ray or ultrasound to focus shockwaves through your skin to break the stone into pieces that are small enough for you to pass in the urine.
Ureteroscopy is recommended for larger stones or if ESWL is unsuccessful. The surgeon passes a ureteroscope (a thin tube ending in a telescope) through your urethra and bladder into the ureter, and breaks up the stone using a laser. The fragments of stone either pass by themselves, or are removed by a grasping tool passed through the ureteroscope.
The final option is a keyhole operation (percutaneous nephrolithotomy or PCNL), in which a ‘telescope’ is passed through your skin and into the kidney. The surgeon then breaks up the stone using laser or ultrasound.
Will I get another kidney stone?
A few people have just one kidney stone in their lifetime, but generally if you have had one stone, you are likely to have another. The risk varies, but on average one in every two people will have another stone within 10 years.
Recommended lifestyle changes to help reduce the risk of another stone are listed in Table 2. These lifestyle measures are not a cure, but drinking more water in particular should reduce your risk of recurrence.
“However, it does depend on the individual—for example, if you are on dialysis there is no point in drinking more than your fluid allowance, because the water will not reach your kidneys and so will not help to prevent stones. And everyone should be carefully assessed to find out why they developed the stone in the first place”, adds Shabbir.
All children and young people aged under 16 should be referred to a specialist nephrologist or urologist. Referral arrangements for adults vary, depending on where you live.
Shabbir advises kidney patients who have had a stone to ask their nephrologist about referral to a specialist kidney stone clinic. He strongly recommends against paying for the type of screening offered online.
The wrong treatment can make your stones worse
Some companies claim to be able to diagnose the cause of your kidney stone if you send them a urine sample. In my view, this is not optimal. Urine testing is useful, but you cannot interpret the results in isolation from the individual patient,” he says.
When people are referred to Shabbir’s specialist clinic, he asks about their lifestyle and medical history, including medicines. You will also be asked to do a 24- hour urine collection, and have blood tests to check your kidney function and the presence of substances that could lead to kidney stones. These results will often suggest the cause of your problem, especially if you have kept the stone.
Specialist kidney stone clinics accept referrals from all over the country, but you may not need to travel to a specialist centre. The basic tests can be done at your local kidney clinic, and results will tell the specialist whether they need to see you.
Shabbir says: "Depending on the results of your tests, I can advise you on specific lifestyle measures and other treatments. This is why it's important for you to be referred appropriately, rather than being left to search the internet for treatments that claim to prevent kidney stones and often cost a great deal of money.
"The wrong treatment can make your stones worse. Potassium citrate, for example, can be helpful if you have calcium oxalate stones, but can make some types of calcium phosphate stone much worse. And taking potassium citrate is risky without the medical supervision if you are on a potassium-restricted diet or are taking medicines like ACE inhibitors."
Recent National Institute of Health and Care Excellence (NICE) guidelines on managing kidney stones highlighted the pressing need for more research to test medical and surgical treatments, and measures to prevent recurrence of kidney stones. Clinical trials are now under way and, according to Shabbir, they highlight another important reason for referral to a specialist.
"If you are suitable for one of the treatments that is being tested, a specialist centre can arrange for you to be invited to enter the appropriate clinical trial. Information from these trials will give us important evidence about the impact of kidney stones on people;s lives. As always, money is tight in the NHS, so patients and professionals must work in partnership to make the case that kidney stones are an important problem that deserves more investment in prevention and treatment," he concludes.
NOTE: This article was first published in November 2019 in Issue 7 of our Kidney Matters magazine
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