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Kidney stones

What are kidney stones and what are they made of?

When substances normally present in the urine in small quantities reach

high concentrations they may accumulate and solidify, forming kidney stones.

There are four main types of kidney stones. Stones containing high levels

of calcium are the most common, accounting for 75-80% of all kidney stones.

These are most often combined with a substance called oxalate to form a

compound called calcium oxalate. Uric acid stones (the substance that

causes gout) make up about 5-10%, struvite stones 10-20% (stones associated

with specific types of urinary tract infection), and a very small percentage of

stones are mainly comprised of a substance called cystine.

A GUID E FOR PATIENTSHE KIDNEY10. Kidney stones

There are fourmain types ofkidney stones.Stones containing

high levels ofcalcium are themost common,accounting for7580% of allkidney stones.

What do kidney stones look like?

Kidney stones may be as small

as a grain of sand or as large

as a pearl. Some stones are even

as big as golf balls. Stones may

be smooth or jagged. They are

usually yellow or brown.

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It is not knownexactly why kidney

stones occur. Thereare many medical

disorders thatpredispose people to

their development.

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How common are kidney stones?

Kidney stones are very common. It is estimated that more than one million

Australians probably have stones in their kidneys, although many will not

be aware of the fact. Kidney stones are responsible for more than 20,000

hospital admissions each year in Australia. These admissions to hospital are

mainly for management of severe pain or because the stones are causing

a blockage within the urinary tract - ureteric obstruction.

Kidney stones are twice as common in men as in women and are also more

common in people who live in hot, dry climates, presumably because they

sweat more and have more concentrated urine.

Why do kidney stones develop?

It is not known exactly why kidney stones occur. There are many medical

disorders that predispose people to their development. These conditions

include gout, hyperparathyroidism, polycystic kidney disease and recurrent

urinary tract infections. In other cases, abnormalities in the constituents ofurine appear to be the underlying problem. The urine may contain

excessive amounts of constituents that make up kidney stones such as

calcium or uric acid.

Alternatively, the urine may not contain high enough concentrations of

substances such as citrate, which prevent some types of kidney stones

from forming.

Bladder Stones

Bladder stones grow slowly and

often cause no symptoms until

they are large. They may block

the outlet of the bladder,

or cause bladder infections.

Bladder stones

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Kidney Stones continued...

How are kidney stones diagnosed?

Many kidney stones are found incidentally on X-ray or ultrasound of the

abdomen or kidneys.

In most cases, the patient with a kidney stone suddenly develops pain

in the side or back, just below the ribs. This pain is known as renal colic.

The pain may travel down towards the groin and may be very severe.

It may be accompanied by feeling very unwell, loss of appetite, vomiting

and blood in the urine (haematuria).

The pain caused by kidney stones is due to the stone passing from the

kidney, where it is formed, down through the ureter towards the bladder.

The ureter is narrow and can easily be blocked by the kidney stone.

This is called ureteric obstruction and can cause severe pain.

When this happens, most people immediately seek the advice of a doctor.

After questioning the patient, the doctor will suspect the presence of a

kidney stone and arrange for special X-rays to be performed. These will

confirm the presence of a kidney stone in most cases. Occasionally,

very small stones can be passed without causing pain.

What other effects do kidney stones have?

Besides pain (renal colic) due to a kidney stone temporarily blocking or

partially blocking the ureter (ureteric obstruction), kidney stones can also

predispose to urinary tract infections. Urinary tract infections occurring in

the presence of kidney stones can be very difficult to eradicate. Sometimes,if a stone blocks a kidney for a prolonged period of time, the kidney may

be irreversibly damaged.

How can kidney stones be treated?

Firstly, adequate pain relief is achieved with powerful painkillers. Thereafter,

the treatment of kidney stones varies according to their size and their

position in the urinary tract as determined by special X-rays.

Small stones that are not causing significant blockage and are not associated

with infection can be managed by increasing fluid intake and taking painkillers.Most of these less serious kidney stones will be passed without any further

treatment. Stones smaller than 5 millimetres in diameter have an 80%

chance of passing spontaneously.

Small stones thatare not causingsignificant blockageand are notassociated withinfection can bemanaged byincreasing fluid intakeand taking painkillers.

Most of these lessserious kidney stoneswill be passedwithout any further

treatment.

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Sicker patients need to be admitted to hospital. Most of these patients

will require pain relief, medication to stop them vomiting and intravenous

fluid to prevent dehydration and some will need a small operation to unblock

the affected kidney. This is either performed by a radiologist in the X-ray

department or by a urologist in the operating theatre.

The radiologist unblocks the kidney using what is called a percutaneous

nephrostomy tube inserted through the skin just below the ribs. The urologist

unblocks the kidney using a special telescope called a cystoscope, which is

passed through the urethra into the bladder, from where special drains

known as stents can be used in the ureter to unblock the kidney.

Sometimes, larger stones in the kidney or upper ureter may be suitable

for shattering with shock waves (shock wave lithotripsy).

Small stones that are found incidentally on X-ray in the kidneys can be

monitored and treated conservatively. Stones that are growing or are large,

may be suitable for shock wave lithotripsy

In most cases, people who have suffered a kidney stone will subsequently

undergo specialised blood and urine tests to establish the exact cause of

their kidney stones. The results of these tests, though sometimes

inconclusive, can be very useful in guiding treatment.

If an abnormality is found in these screening tests, some things like drinking

more water, following the right diet (see later in this chapter) and/or

medication may help to reduce the likelihood of recurrence.

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Kidney stones continued...

Can stones be dissolved?

Most stones (75-80%) are made of calcium oxalate and do not dissolve.

About 10% are made of uric acid and these may dissolve in an alkaline

urine (making the urine less acid). This can be achieved with Ural or

bicarbonate tablets.

What can I do to prevent kidney stones?

The most important factor in the prevention of kidney stones is to increase

urine volume. Fluid intake should be increased so that 2-3 litres of urine is

passed each day. As the urine is most concentrated during the night,

some people need to drink enough to make them pass urine during the

night and even drink more fluid when they get up to urinate.

Other measures to prevent stones will depend on the type of stone and

the abnormalities found in the urine.

What is the effect of diet?

Diet is probably not as important as previously thought in the development

of kidney stones, particularly calcium stones. In the past, people forming

calcium-containing kidney stones were often advised to restrict their calcium

intake, but studies have shown that this does not prevent kidney stones nor

reduce the amount of calcium in the urine. Reduction in salt intake may be

beneficial, as this will help reduce urinary calcium levels. People forming uric

acid kidney stones may be advised to lose excess weight, avoid certain foods

such as red meat and avoid excess alcohol. Certain dietary fads and excess

intake of vitamin D and vitamin C can be associated with kidney stones.

How long do I need to take treatment?

Once kidney stones have formed and if a metabolic abnormality has been

detected, treatment will need to be life-long. Stopping treatment will make

further stone formation likely.

The mostimportant factorin the preventionof kidney stones isto increase urinevolume. Fluid intakeshould be increasedso that 2-3 litresof urine is passed

each day.