4urology

Extracorporeal ShockWave Lithotripsy or ESWL works on the same principle as an operatic singer who sings at a certain frequency and makes a glass shatter. In ESWL ultrasound waves are focused on the kidney stone and make it vibrate and fragment into smaller pieces that can be passed normally via the urinary tract.

ESWL fragmentation of calculi	Passing smaller fragments after ESWL

The lithotriptor attempts to break up the stone with minimal collateral damage by using an externally-applied, accurately focused, high-intensity acoustic pulse.

The Dornier Lithotriptor S

Extracorporeal lithotripsy works best with stones between 4 mm and 2 cm in diameter that are still located in the kidney. It can be used to break up stones which are located in a ureter too, but with less success.

The patients undergoing this procedure can see for themselves the progress of their treatment. If allowed to view the ultrasound or x-ray monitor, they may be able to see their stones change from a distinct bright point (or dark spot depending on whether the fluoro unit is set up in native or bones white) to a fuzzy cloud as the stone is disintegrated into a fine powder.

ESWL is the least invasive of the common place modalities for definitive stone treatment, but provides a lower stone-free rate than other more invasive treatment methods, such as ureteroscopic manipulation with laser lithotripsy or percutaneous nephrolithotomy (PCNL). The passage of stone fragments may take a few days or a week and may cause mild pain. Patients are instructed to drink as much water as practical during this time. Patients may also be advised to void through a sieve (tea strainer) in order to capture stone fragments for analysis.

A patient of the procedure has equated the after effects to "a punch to the kidney" (pain while urinating, sometimes with blood).

ESWL is not without risks. The shock waves themselves, as well as cavitation bubbles formed by the agitation of the urine medium, can lead to capillary damage, renal parenchymal or subcapsular hemorrhage. This can lead to long-term consequences such as renal damage and hypertension.

Flexible or rigid ureterorenoscopy, open surgery or observation to allow spontaneous passage.

You will usually be admitted on the same day as your treatment. It may be useful to bring your own dressing gown to wear over your hospital gown. We will check your urine when you arrive on the unit to make sure that you do not have a urinary tract infection. If you have an infection the treatment may be delayed for you to have a course of antibiotics.

Occasionally a ureteral stent (a kind of expandable hollow tube) may be placed at the discretion of the urologist prior to your first treatment. This will require an admission to hospital prior to your first session of ESWL. The stent allows for easier passage of the stone by relieving obstruction and through passive dilatation of the ureter.

On arrival, an X-ray may be taken to confirm the presence of your stone(s).

You will be asked to drink only clear fluid before the treatment and, immediately before the procedure, you will be given an oral pain-killer and an anti-inflammatory suppository.

Please be sure to inform your Urologist in advance of your surgery if you have any of the following:

• an artificial heart valve
• a coronary artery stent
• a heart pacemaker or defibrillator
• an artificial joint
• an artificial blood vessel graft
• a neurosurgical shunt
• any other implanted foreign body
• a prescription for Warfarin, Aspirin or Clopidogrel (Plavix®)
• a previous or current MRSA infection

Normally, no anaesthetic is necessary and you will be awake throughout the procedure. Treatment is normally carried out with analgesia but children usually require a general anaesthetic.

The treatment will be monitored by a nurse and a specialist radiotherapist trained in lithotripsy. The shock waves can cause deep discomfort in the kidney and a sensation of being flicked with an elastic band on the skin of your back. If this proves excessively painful, additional intravenous painkiller can be administered during the treatment. Treatment normally lasts between 30 and 60 minutes.

The patient lies down on the table, with the back supported by a water-filled coupling device placed at the level of kidneys.

Patient position	Coupling

A fluoroscopic x-ray imaging system or an ultrasound imaging system is used to locate the stone and aim the treatment and the patient is positioned so that the stone recieves the focused shock wave. The treatment usually starts at the equipment's lowest power level, with a long gap between pulses, in order to accustom the patient to the sensation. The frequency of pulses and the power level are then gradually increased, so as to break up the stone more effectively. The final power level usually depends on the patient's pain threshold. If the stone is positioned near a bone (usually a rib in the case of kidney stones), this treatment may be more uncomfortable because the shock waves can cause a mild resonance in the bone which can be felt by the patient. The sensation of the treatment is likened to an elastic band twanging off the skin. Occasionally the patient may need to be sedated during the procedure.

The successive shock wave pressure pulses result in direct shearing forces, as well as cavitation bubbles surrounding the stone, which fragment the stones into smaller pieces that then can easily pass through the ureters. The process takes about between 20 and 60 minutes during which time you can listen to CDs on headphones (you can bring your own CDs if you wish). During the treatment you will be aware of the noise of the pressure wave generation but this sound is not disturbing. You will be required to lie still through the treatment so that the position of the stone does not alter.

It is not unusual for more than one treatment to be necessary and we treat most kidney stones with 3 sessions and most ureteric stones with 2 sessions.

Complications are unusual after ESWL, occasionally there is a small amount of bruising of the skin. Immediately after treatment many people notice they pass a small ammount of blood in their urine but this usually clears up to a light pink colour within a few hours. If you have significant blood in the urine we will ask you to saty on the ward until it clears.

Immediately after the treatment, you may feel quite drowsy. You will normally be taken back to the ward to recover with a cup of tea or coffee. The Specialist Nurse will also perform routine post-operative checks.

As soon as you have recovered from the treatment, you will be able to go home but you must bring someone with you to escort you home; you should not attempt to drive yourself because of the effects of the treatment and/or sedation.

Painkillers will be given to you before your discharge.

The average hospital stay is less than 1 day.

When you get home, you should drink twice as much fluid as you would normally to flush your system through and minimise any bleeding or infection. Painkillers should be taken as necessary and you must complete the course of antibiotics.

Some blood in the urine is normal for 48-72 hours. If you develop bruising/blistering in your loin or on your abdomen, simple skin creams will usually ease any discomfort and the bruising normally resolves within 7 days.

When you leave hospital, you will be given a “draft” discharge summary of your admission. This holds important information about your inpatient stay and your operation. If, in the first few weeks after your discharge, you need to call your GP for any reason or to attend another hospital, please take this summary with you to allow the doctors to see details of your treatment. This is particularly important if you need to consult another doctor within a few days of your discharge.

There may be some discomfort for up to a couple of weeks as stone fragments pass.This is usually controlled by simple pain killers but if these do not work or if you feel you have any flu-like symptoms, fevers or shakes, with a high temperature or any other complaint suggestive of urinary tract infection, please contact the unit between 8am and 5pm. If out of hours or if you fail to make contact with the unit, contact your GP and give him/her the information sheet supplied on discharge.

Some of the passed fragments of a 1 cm calcium oxalate stone that was smashed using lithotripsy.

Also if you develop severe pain on passing urine, inability to pass urine or worsening bleeding, you should contact your GP immediately. Small blood clots or stone fragments may also pass down the ureter from the kidney, resulting in renal colic; in this event, you should contact your GP immediately.

Common Side-effects (greater than 1 in 10)

• Bleeding on passing urine for a short period after the procedure
• Pain in the kidney as small fragments of stone pass after treatment (20%)
• Urinary tract infection due to bacteria released from the stone during fragmentation, requiring antibiotic treatment (10%)
• Bruising or blistering of the skin in the loin or on the front of the abdomen
• Need for repeated ESWL treatments (15-20%)
• Failure to fragment very hard stone(s) requiring an alternative treatment (less than approximately 14%)

Occasional Side-effects (between 1 in 10 and 1 in 50)

• Severe infection requiring intravenous antibiotics (less than 1%) and sometimes drainage of the kidney by a small drain placed through the back into the kidney
• Stone fragments occasionally get stuck in the tube between the kidney and the bladder requiring hospital attendance and, occasionally, surgery to remove the stone fragments

Rare Side-effects (less than 1 in 50)  

• Kidney damage (bruising) or infection needing further treatment
• Recurrence of stones (less than 1%)

You will be informed before your discharge of any follow-up arrangements. This will usually involve either further lithotripsy, operative surgery or a simple follow-up outpatient appointment when a further X-ray will be taken.

If you have a stent in place, you may be given an appointment for removal of the stent in the Day Surgery Unit under local anaesthetic If this is appropriate.

You can prevent further stone recurrence by implementing changes to your diet and fluid intake. If you have not already received a written leaflet about this, contact your named nurse, the Specialist Nurse in outpatients, your Consultant or click on this link.

ESWL works in approximately 3 patients out of 4. If the stone fails to fragment it may be necessary to proceed to a urteroscopy under a seperate admission. This involves general anaesthetic and an overnight stay in hospital. For more information on ureteroscopy click here.