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KIDNEY STONES (KIDNEY STONE DISEASE)

1. What do the kidneys do?

The kidneys are two bean-shaped organs that sit on either side of your spine, just under the ribs in your back. Their main jobs are:

• To filter waste products and extra fluid out of the blood

• To keep the balance of water and salts in the body

• To make some important hormones (for blood pressure and red blood cell production)

The liquid produced by this filtering process is called urine. Urine travels from the kidneys through thin tubes called ureters, down to the bladder, and then leaves the body through the urethra when you pass urine.

1. What is a kidney stone? How common is it?

A kidney stone is a hard lump that forms inside the kidney when minerals in the urine stick together and crystallise.

• About 1 in 10 people will have a kidney stone at some point in their life.

• It is most common between the ages of 30 and 60.

• It is slightly more common in men, but women are also affected.

Modern lifestyle plays a big role: not drinking enough water, sitting too much, eating a lot of processed food and salt, and being overweight all increase the risk of stones.

1. How do kidney stones form?

Your urine contains many dissolved substances such as calcium, oxalate and uric acid. Normally, these stay dissolved and are passed out in the urine without any problem. Stones tend to form when:

• You do not drink enough water (so there is less fluid but the same amount of minerals in the urine)

• There is a blockage or narrowing in the urinary tract, and urine cannot flow freely

• Some substances in the urine are higher than normal (for example, too much calcium in the urine, called hypercalciuria)

• You have repeated urine infections

When urine is too concentrated, these substances can come out of solution and form tiny crystals, like grains of sand. This is what people often call “passing gravel”. Over time, these crystals can stick together and grow into larger stones.

1. Types of kidney stones

The main types of kidney stone are:

• Calcium stones

  • The most common type.

  • Usually made of calcium oxalate or calcium phosphate.

  • High salt intake, certain metabolic problems, some medicines, high-dose vitamin D and family tendency can increase the risk.

• Uric acid stones

  • More likely in people who eat a lot of meat, who have gout or who have very acidic urine.

• Struvite stones (infection stones)

  • Usually related to repeated urine infections.

• Cystine stones

  • Rare.

  • Due to an inherited (genetic) problem that causes too much cystine to leak into the urine.

Finding out the stone type helps to guide prevention. If possible, any stone you pass or that is removed during surgery should be sent for stone analysis.

1. What symptoms can kidney stones cause?

Kidney stones sometimes cause no symptoms at all and are found by chance when you have a scan for another reason.

When they do cause symptoms, common ones are:

• Sudden, severe pain in the side or back (often called renal colic)

  • The pain may spread from the back towards the tummy, groin or, in men, towards the testicle.

• Blood in the urine (sometimes visible, sometimes only seen on a urine test)

• Needing to pass urine more often or burning when passing urine

• Nausea and vomiting

• A feeling of bloating or discomfort in the abdomen

The nerves that supply the kidneys and urinary tract share pathways with those from the stomach and intestines, so stone pain is often mistaken for “stomach pain”, “gas cramp” or “bowel colic”.

1. When should I go to A&E (emergency)?

If you have a known or suspected kidney stone and any of the following, you should seek urgent medical help:

• High temperature (38 °C or above) together with stone pain

• Shivering, shaking, feeling very unwell

• Only one working kidney (born with one kidney, one kidney removed, or one kidney not working)

• Possible blockage of both kidneys

• Severe pain that does not improve with strong painkillers

• Not passing any urine at all

These can be signs of a serious infection or severe blockage. A stone plus infection is a urological emergency and can be life-threatening if not treated quickly.

1. How are kidney stones diagnosed?

It is not safe to rely only on symptoms to diagnose a kidney stone. The stone must be seen on a scan.

Common tests used are:

• Ultrasound scan

  • Usually the first test done.

  • Looks at the kidneys, ureters and bladder.

  • Shows if there is a stone, swelling of the kidney (hydronephrosis) or other problems.

  • Advantages: quick, painless, no radiation.

  • Limitations: small stones or stones in certain positions may be missed, and the exact size and location are not always clear.

• CT scan (non-contrast CT, often called a “stone CT”)

  • This is the gold-standard test for kidney stones.

  • Shows the exact size, number and position of stones.

  • Shows how much blockage there is in the urinary tract.

Other tests may be used in special cases:

• Nuclear medicine scans (renal scintigraphy) to measure how well each kidney is working

• Older tests like intravenous urography are now rarely used

1. What tests should be done if I have a kidney stone?

Most people with kidney stones will need:

• Urine tests

  • Routine urine test to look for blood, infection and crystals

  • Urine culture if infection is suspected

• Blood tests

  • Urea and creatinine to check kidney function

  • Electrolytes (such as sodium, potassium)

  • Uric acid, calcium and other relevant tests

• Imaging

  • Ultrasound and/or CT scan, depending on the situation

People who have:

• Recurrent stones

• Stones at a young age

• A single kidney

• A strong family history of stones

should usually have more detailed “metabolic” tests. These may include:

• A 24-hour urine collection (you collect all urine you pass over 24 hours, which is then analysed in the lab)

• Stone analysis (chemical analysis of any stone that is passed or removed)

These tests help to plan long-term prevention.

1. Do all kidney stones need treatment?

No. Not all stones need immediate treatment.

In general:

• Small stones that sit in the kidney, do not block the flow of urine and cause no symptoms can sometimes be safely monitored with regular scans.

• Stones that are large, growing, causing repeated pain, reducing kidney function, causing repeated infections or blocking urine flow usually need active treatment.

The decision to treat or monitor depends on stone size, location, number of stones, your symptoms, your kidney function and any other medical problems. This decision should be made together with your urologist.

1. Treatment options for kidney stones

a) Medical treatment (watchful waiting and helping the stone to pass)

Many stones up to about 5 mm in size may pass on their own.

During this time:

• Strong painkillers and antispasmodic medicines are used to control pain.

• You are encouraged to drink plenty of fluids, unless your doctor advises otherwise.

• In some cases, medicines that relax the ureter (for example, tamsulosin) may be prescribed to help the stone pass.

This is sometimes called “medical expulsive therapy”.

Not every stone is safe to “wait and see”. In some situations, waiting can harm the kidney. The decision to wait must be made by your doctor and you should be monitored during this period.

b) ESWL (Extracorporeal Shock Wave Lithotripsy)

ESWL uses shock waves from outside the body to break the stone into smaller pieces.

• You lie on a special table and the machine sends shock waves through the skin and tissues, focusing them on the stone.

• The stone is broken into smaller fragments.

• These fragments then pass out naturally in the urine over days or sometimes weeks.

Often, a mild sedative or pain relief is given during the procedure.

Possible downsides:

• The stone may not break into very fine pieces, and some fragments can still be large enough to cause pain.

• Passing fragments can be painful.

• Urine infections can occur.

• Occasionally, many small fragments collect in the ureter, causing a blockage (“steinstrasse” or stone street), and extra treatment may be needed.

c) Ureteroscopy (endoscopic treatment of ureteric stones)

The ureter is the narrow tube that carries urine from the kidney to the bladder. Stones that become stuck in the ureter and do not pass may be treated with ureteroscopy.

• A thin telescope (rigid or flexible ureteroscope) is passed through the urethra, into the bladder and then up into the ureter.

• The stone is seen directly on the camera.

• A laser (most commonly Holmium laser) or a pneumatic device is used to break the stone.

• The pieces may be removed with tiny baskets or left to pass if they have been reduced to fine fragments.

Generally:

• There is no cut on the skin; it is a keyhole procedure through the natural urinary passage.

• Most patients go home the same day or the following day.

Often a temporary soft plastic tube called a ureteric stent (Double-J stent) is left in place:

• This keeps urine flowing freely

• Reduces swelling

• Helps stone fragments to pass

The stent is usually removed after a few days or weeks with a short day-case procedure.

d) Flexible ureterorenoscopy / RIRS (endoscopic kidney stone surgery)

In this modern “keyhole from below” technique:

• A very thin, flexible telescope is passed through the urethra and bladder, up the ureter, into the kidney itself.

• The tip of the scope can bend in different directions, allowing access to almost all parts of the kidney.

• The stone is seen directly.

• A laser is used to break the stone into dust or small fragments.

• Some pieces are removed; the rest pass in the urine over time.

Advantages:

• No cut in the skin.

• Usually a short hospital stay and quick recovery.

• Very effective for many small and medium-sized kidney stones.

It does require specialist equipment and an experienced team. As with all procedures, there are potential risks such as infection, bleeding, or scarring in the ureter, which your surgeon will explain.

e) Percutaneous nephrolithotomy (PCNL, keyhole surgery through the back)

For large or complex kidney stones, especially stones:

• Larger than about 2 cm

• Filling a large part of the kidney (so-called “staghorn” stones)

it may be better to remove them through a small cut in the back.

In PCNL:

• A small incision is made in the skin of the back, near the kidney.

• A tract is created into the kidney and widened to allow a telescope and instruments to pass.

• The stone is broken up and the pieces are removed directly.

Compared with old-style open surgery, PCNL uses a much smaller cut and recovery is faster, but:

• There is a risk of bleeding, so blood must be available if needed.

• A hospital stay of 2–4 days is common.

f) Open surgery

Traditional open surgery for kidney stones is now rarely needed, thanks to modern endoscopic and keyhole techniques.

It may still be considered if:

• The stone is extremely large (for example, larger than 4 cm), and other methods are unlikely to clear it in one session

• The anatomy makes keyhole access very difficult or impossible

• There are severe internal scars from previous operations

Even in these situations, open surgery is used only in selected cases.

1. What should I do while waiting to pass a stone?

If your urologist has recommended watching and waiting:

• Drink small amounts of water regularly throughout the day, unless you have been told to restrict fluids. Your urine should be pale yellow or almost clear.

• Take your prescribed painkillers and any other medicines as directed.

• Try to catch the stone: urinate through a tea strainer or special stone filter when possible. This allows the stone to be analysed later.

• Seek urgent help if you develop severe pain, fever, shaking, feel very unwell, cannot pass urine or if your symptoms suddenly worsen.

1. Do kidney stones come back? How can I prevent them?

Unfortunately, kidney stones often have a tendency to come back. Many patients who have had one stone will develop another one within 5–10 years if no preventive steps are taken.

To lower the risk:

a) Fluid intake

• Aim to produce at least 2–2.5 litres of urine per day.

• In practice, this usually means drinking around 2.5–3 litres of fluid per day, more if you sweat a lot or live in a hot climate.

• Water should be the main drink.

• Sugary drinks, high-fructose drinks, energy drinks and large amounts of fizzy drinks may increase stone risk.

b) Diet

General tips (these may be adjusted according to your stone type):

• Reduce salt intake (avoid heavily salted foods, processed foods, crisps, cured meats, very salty cheeses, pickles).

• Limit large amounts of animal protein (especially red meat and organ meats). A Mediterranean-style diet is often recommended.

• Do not cut out dairy products completely unless told to do so. Normal amounts of milk and yoghurt are usually fine and may even help protect against stones in some people.

• Do not take high-dose vitamin D, calcium or vitamin C supplements without medical advice.

• Depending on your stone type, you may be advised to reduce foods high in oxalate (such as spinach, chard, rhubarb, some nuts and chocolate).

c) Metabolic assessment and medication

If you have recurrent stones, or other risk factors, your urologist may recommend a full metabolic work-up:

• 24-hour urine collection

• Stone analysis

• Detailed blood tests

Based on the results, specific medicines may be used to reduce the chance of new stones forming, for example:

• Medicines to reduce calcium leak into the urine

• Medicines to reduce uric acid levels

• Medicines to make the urine less acidic (more alkaline), such as potassium citrate

1. Guidelines and trusted sources

The information on this page is based on clinical experience and on up-to-date national and international guidelines, including:

• European Association of Urology (EAU) guidelines on urolithiasis (kidney stones)

• American Urological Association (AUA) kidney stone guidelines

• Patient information resources from the NHS and major teaching hospitals

This text is for general information only. Every patient is different. The best treatment and follow-up plan for you will depend on:

• The size, number, position and type of your stones

• How well your kidneys are working

• Your general health and other medical conditions

• Your personal preferences

You should always discuss your own situation in detail with a urology specialist, who can give individual advice and agree a treatment plan with you.