Kidney stones: How are they managed?

Do you have kidney stones? You may have various questions about how they're managed.

Here to assist is highly-skilled consultant urological surgeon based in York, Mr Antoine Kass-Iliyya.  He speaks to Top Doctors all about this common condition in expert detail, as well as providing the different treatment options available.

What are kidney stones?

A kidney stone is a hard material that is made up from a high concentration of chemicals in the urine.

How do kidney stones form?

Kidney stones form when the urine is over-saturated with certain chemicals.

Up to a certain concentration, the chemicals are usually melted in the urine and no stone could be formed. When the chemicals reach a higher concentration, our body can still prevent stone formation, thanks to some other urine ions or buffers that will ensure solubility of those chemicals, these include citrates, for example.

However, when the concentration of the chemicals is even higher than what the body and the anti-stone buffers could cope with, the stones start to form, this concentration is known as the formation product (Kf). 

There are risk factors for stone formation, and these include intrinsic and extrinsic factors.

Intrinsic factors

• Age: The peak incidence of stones occurs between the ages of 20-50
• Sex: Kidney stone disease is more common in males compared to females. However, the gap continues to narrow.
• Genetic: 25 per cent of patients with kidney stones have a family history of stone disease.

Extrinsic factors

Geographical location

Renal stone disease is more common in hot climates, although the western lifestyle (excess food, inadequate fluid intake, limited exercise) means that the incidence of stones could also be high in temperate climates like northern Europe and Scandinavia, for example.

Seasons

Ureteric stones are more common during the summer, because of the higher urinary concentration in the summer which encourages crystallization.

Water intake

This is perhaps the most important dietary factor for stone formation, low fluid intake (<1200ml/day) predisposes to stone formation.

Diet

High animal protein (meaty products) and table salt increases the risk of stone formation. There is a wide misconception that calcium or dairy products increase the risk of stone formation, but evidence suggests that people who have low calcium diet are at a higher risk of developing kidney stones. Therefore, we recommend a moderate consumption of calcium (1000mg or 1 g a day)

Occupation

Sedentary occupations (desk jobs for example) increase the risk of stone formation.

Can kidney stones travel outside of the kidneys?

Unfortunately, yes.

Our kidneys are made of a meaty part which is called the renal cortex. It's responsible for producing urine by filtering the blood stream from the toxins, and a hollow part, which is called the collecting system which collects all the urine that is produced by the cortex.

The collecting system is made of the renal calyces (small pockets of space) and the renal pelvis (a big pocket of space). All the calyces join into the renal pelvis.

The renal pelvis is connected to the ureter which is a 25-30cm (8-10 inches) long muscular tube that joins the kidney to the bladder and constantly squeezes the urine downstream.

Kidney stones usually form in the renal calyces and then pass on to the renal pelvis and the ureter. When they reach the ureter, they block the flow of urine and causes the ureter to expand which causes the severe pain.

What are the signs of a stone blockage in the ureter?

This causes a colicky pain with each wave of ureteric squeeze to overcome the blockage. This is called a renal colic which is very painful (some women describe it as worse than a childbirth pain)

The pain typically starts in the flank and travels down to the groin.

Other signs of renal colic include;

• Visible or non-visible blood in the urine;
• Bladder irritation when the stone reaches the lower part of the kidney pipe, the symptoms include frequency and urgency to wee and producing only small amounts of urine;
• Urosepsis. This is not very common; it happens when the urine in the blocked kidney becomes infected. This is a serious condition and should be treated as an emergency due to the risk of the infection spreading to the blood stream and causing septicaemia (blood poisoning) which could be life threatening, some patients might require admission to intensive care unit.

How are stones effectively treated?

This really depends on the size and the location of the stones as well as the age of the patient. Please see below for more details.

Kidney stones

All kidney stones that are less than 5 mm could be monitored with no need for an immediate treatment. However, treatment is often encouraged in young people to prevent a future renal colic or the need for intervention the risk of which is around 20% over a three-year period. (Burger, 2004 study)

If the stones are larger than 5mm and the patient is reasonably fit, treatment is encouraged.

Treatment options include:

• Extracorporeal Lithotripsy (ESWL)
• Ureteroscopy and laser treatment
• Percutaneous Nephrolithotomy (PCNL)
• Open surgery
• Medical therapy

Extracorporeal Lithotripsy (ESWL)

This technique entails destroying the stones from outside using a shockwave that is generated in a machine.

The treatment does not require a general anaesthetic and could be delivered in an outpatient setting. Patients will require analgesia on the day.  

The patient usually lies flat on a table and the stone is located with an X-ray by an experienced radiographer and the shockwave is targeted towards the stone using a special machine that comes very close to the skin using a gel pad. The shockwave session lasts around 45 to 60 minutes and patients often require two sessions to destroy the stone.

This option is offered for stones that are up to 1cm in the kidney and that are in a favourable location (middle or upper part of the kidney, not as effective in the lower part of the kidney)

Overall success rate is around 50-70 per cent.

Side effects include:

• Pain;
• Blood in the urine afterwards for few days, with an up to 40 per cent chance;
• Renal colic if a stone fragment drops down and gets stuck in the kidney pipe. There is a 10 per cent chance of this;
• For stones larger than one cm, this option is less effective.

Ureteroscopy and laser treatment

This technique entails destroying the stone with a direct vision using a telescope from the inside which goes through the water pipe into the bladder and then the kidney pipe and eventually the kidney.

Once the stone is visualised with the camera, a small laser fibre is inserted through the camera (1mm in diameter) and the stone is destroyed into small fragments under vision. The fragments could then be grabbed with a basket and removed or if too small they will pass spontaneously.

This option is often more effective in clearing the stones compared to the shockwave, but it is more invasive with small risks of general anaesthetic complications <1% and trauma to the kidney pipe 1-2 per cent. The patient might need to have a stent temporarily after this procedure. (A stent is a plastic long tube 26cm, that goes from the kidney through the kidney pipe into the bladder; it facilitates drainage of the kidney after surgery if there are multiple fragments or swelling in the kidney pipe).

Side effects include:

• Pain;
• Blood in the urine afterwards for few days, with up to a 70 per cent chance;
• Rarely ureteric injury requiring a stent. There is a 1 per cent chance of this.

The overall success rate is between 80-90 per cent.

For stones larger than 1 cm, multiple operations might be required to clear the stones.

Percutaneous Nephrolithotomy (PCNL)

This option is usually reserved for stones that are larger than 2cm in diameter, this procedure is also performed under general anaesthetic.

The patient lies in a prone or supine position (Depending on the anatomy) to facilitate access to the kidney.

Access is gained through the skin of the loin by an experienced radiologist or a urologist using special instruments to create a track between the skin and the kidney so that instruments could be passed inside the kidney. The stone is destroyed using ultrasonic shockwaves.

This option is the most effective option for clearing large stones (>2cm) in one surgery and increasingly smaller stones (1-2 cm) are now being treated with PCNL, especially in patients who would like to avoid multiple surgeries.

The downside of PCNL is that it is more invasive surgery with risks of severe bleeding requiring blood transfusion in 2 per cent and rarely embolization of the bleeding vessel <1 per cent (injecting a coil to block the vessel and stop bleeding), sepsis 5%, and rarely a risk of organ injury (bowel <1 per cent, lung 3 per cent)

Open surgery

This is rarely offered these days due to the advancement of the other methods of clearing the stones. However, it still has a role in situations where it is better to avoid multiple surgeries, for example if the stone is very large and multiple PCNL procedures might be required to clear it. It is also offered if the kidney has been severely damaged by the stone and shrunk, in those cases the kidney is removed altogether.

Medical therapy

This option entails trying to dissolve the stones using medications.

This is suitable for uric acid and cystine stones but not for calcium stones. Therefore, ideally the stone (if available) should be analysed first to assess suitability for medical dissolution therapy.

Uric acid stones

Uric acid stones form in concentrated acid urine. Dissolution therapy is based on hydration, urine alkalinization, allopurinol, and dietary manipulation.

Recommendations for treatment:

• High fluid intake 2-3L/day
• Sodium bicarbonate 650mg three times a day  
• Potassium citrate 15-30mL solution three times a day
• Allopurinol 300-600mg/day (if the concentration of uric acid in the urine is high)

Cystine stones

These are usually inherited with a family history of cystine stones.

Recommendations for treatment:

• Diet restriction of methionine (cystine precursor) and of sodium intake to < 100mg/day
• Alkalinization of the urine to pH >7.5 (Potassium citrate)
• High fluid intake
• Drugs
• D-penicillamine (has significant side effects)
• N-acetyl-D-penicillamine
• Tiopronin

Ureteric stones

As mentioned above when the stone drops from the kidney to the kidney pipe (the ureter) it often causes a renal colic (severe often sudden loin to groin pain)

The stone might also cause a blockage and swelling to the kidney and in the worst-case scenario a urine infection in a blocked kidney which could progress to septicaemia (blood poisoning) if left untreated.

How are kidney stones diagnosed?

A CT scan to look for the stone is the best diagnostic test and the most accurate (99 per cent),

How are kidney stones treated?

Analgesia

Options include:

• Paracetamol (Intravenous is often more effective than oral)
• Codeine Phosphate
• Diclofenac suppositories (most effective)
• Morphine (oramorph)

Is surgery always necessary?

If the stone is 6mm or less and the pain settles, a conservative approach might be attempted.

The patients are often sent home with analgesia and then they are reviewed in the outpatient stone clinic in four to six weeks to ensure that the stone has passed.

If the stone is 7 mm or larger, the patients are stay in hospital and an operation is suggested to remove the stone as above (ureteroscopy and laser treatment).

Other reasons to offer surgery are:

• If the pain is not settling despite analgesia;
• If the patient has a single kidney;
• If the patient has stones blocking both kidney pipes;
• If the kidney is blocked and infected.

In those cases, we often achieve kidney drainage first through the skin by inserting a tube into the kidney (called a nephrostomy), a procedure that is done under local anaesthetic by a radiologist (X-ray consultant specialist). The tube is then attached to a bag on the outside to divert the kidney urine away from the blocked kidney pipe. Once the infection settles the outer tube is converted to an inner tube (a stent) using the same skin access to the kidney and the bag is removed.

Extracorporeal shock wave lithotripsy (ESWL) could also be offered acutely in some centres that could provide a hot service.

To arrange an expert consultation regarding kidney stones, arrange a consultation with Mr Kass-Iliyya via his Top Doctors profile.