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Renal calculi

Dr Roger Henderson
Reviewed by Roger HendersonReviewed on 29.04.2024 | 6 minutes read

Renal calculi – often more commonly called kidney stones - are crystals formed from the naturally occurring salts in urine that can sometimes clump together to form a solid lump or ‘stone’. They are common, and every year about 2 people in every 1,000 will have kidney stone symptoms. They are more common in men, almost double than women, and in their lifetime, 1 in 8 men and 1 in 16 women will have pain caused by a kidney stone.

Kidney stones often do not tend to cause many symptoms if they are stationary in the kidney itself, but the real problems usually occur if they move out from the kidney and travel into the ureter – the tube connecting a kidney to the bladder. If this happens, along with causing severe pain, they can block the ureter, leading to potential infection and difficulty passing urine. They can also carry the risk of preventing the kidneys from working effectively, either in the short term or with more long-term consequences.

What do kidney stones feel like? The typical pain associated with kidney stones is felt from the loin to the groin. This is from the side of the back, radiating around to the front lower part of the abdomen. People sometimes feel the pain travelling into the vagina, testicle or tip of the penis, and they may also see blood in their urine.

Most people report the pain of kidney stones to be excruciating, coming in waves and spasms to double them over until it passes after a few seconds or minutes before returning again and is often so severe it makes them vomit. The waves of pain happen when your ureter is blocked, but this muscular tube tries to force the stone along it by squeezing.

If you have classical-sounding pain, along with blood in your urine, your doctor may arrange a scan to see whether there is any evidence of kidney stones.

What causes the stones?

  • Renal calculi sometimes form because there is an imbalance in certain chemicals produced in your urine, such as calcium. This can be due to a medical problem or certain regular medications but in most cases there is no obvious cause found as to why a kidney stone has formed.
  • Stones are more likely to develop if you are dehydrated or don’t drink enough fluids, as this dilutes the stone-forming chemicals, to be passed out in the urine.
  • Medical textbooks sometimes describe a typical kidney stone patient being a middle-aged chef who works in a hot environment and doesn’t drink enough water during a busy evening of work.
  • The moral of that story is to carry your bottle and stay hydrated.
  • Having repeated attacks of urine infections also increases the risk of kidney stones, as does having a close family relative with them, taking diuretics (‘water tablets’), or having an abnormal kidney called polycystic kidney disease (kidney with cysts in it).

When should I see a doctor?

If you think you have a renal calculus, you will need to see or speak to your doctor. You may be looking for some pain relief, and if it is the first time you have had a suspected kidney stone then you will need some sort of imaging to confirm the diagnosis. Scans can include X-rays, ultrasound and CT scans.

If you have had renal calculi before, and have spoken to your doctor about managing them at home if the pain is controlled – you should take care to know when you may need to escalate things.

If you get a fever, you should immediately speak to your doctor or attend the emergency department as this can indicate a blocked and infected kidney due to the stone. If you are unable to pass urine for several hours, you should attend the emergency department urgently.

If you don’t notice the stone pass, you will need to see your doctor to arrange some imaging to check that the stone has passed and is not stuck and potentially causing long term kidney damage by blocking the tube connecting the kidney and bladder.

Your doctor will, of course, consider other causes of tummy pain, including a urine or kidney infection, appendicitis, pelvic inflammatory disease in women or prostatitis in men, or simple severe lower back pain. In fact, some people experience lower back pain after drinking alcohol as this causes further dehydration.

How is it treated?

In many cases, no treatment is needed to pass renal calculi and even stone sizes up to around half a centimetre in diameter can pass out by themselves. This can be very painful though so pain relief can be the only thing required to help get through it. You can take paracetamol or ibuprofen (if just for short term relief) but stronger painkillers can be prescribed by your doctor.

If the stone is large, or if there are other complications such as infection or damage to the kidney and its filtering effects then other treatments may be required. These include shock wave therapy – known as extracorporeal shock wave lithotripsy (ESWL) that uses high-energy shock waves to break up stones that are still in the kidney and which can then be passed out of the body when you pee.

Surgical methods are is sometimes required such as percutaneous nephrolithotomy (PCNL) where a telescope-like device is passed into the kidney under general anaesthetic to break up and remove the stone, or surgical removal if the stone is very large. In the uncommon situation when a stone gets stuck and completely blocks the ureter, a stent can be placed to keep the person safe in the short term. A stent is a tube that is passed from the bladder to the kidney to ensure no blockage or complications occur due to the stone, and urine can pass freely down the ureter and around the stone due to the presence of the stent.

If a kidney stone is made up exclusively of uric acid (about 5% of stones are like this) then dissolving it by drinking lots of fluids and taking medication to make your urine less acidic can sometimes work.

How can I prevent renal calculi?

Staying well hydrated is crucial to putting yourself in the best place possible for avoiding the formation of kidney stones. Make sure that you keep your water intake to at least at the minimum of 2.5 to 3 litres per day to ensure that you are doing everything possible to dilute down any stone-forming products in the urine.

You can also take stock of your hydration level by checking in on your thirst levels, tracking your daily intake of water and also monitoring the colour of your urine – aim for pale straw-coloured urine at all times.

If you take regular medications, you can speak to your doctor to check that none of them could be linked to kidney stone formation. You may also need to avoid drinking excessive amounts of tea, coffee, salt, fizzy drinks and beer which can predispose to certain types of stone formation.

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Dr Roger Henderson
Reviewed by Roger Henderson
Reviewed on 29.04.2024
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