Shockwave lithotripsy

Extracorporeal Shockwave Lithotripsy (ESWL or SWL) was introduced in the 1980's and revolutionised the treatment of urinary stones at the time. In fact, St. Thomas' Hospital was the first NHS hospital to have a shockwave lithotripter in 1984 and used to receive referrals from all across the UK. At that time, the treatment had to be done under general anaesthetic with the patient hoisted into a waterbath. Modern machines are very different, with no large water bath and often done with simple pain-killers only.

The principal is that a shockwave is generated and targeted using either ultrasound or x-ray guidance. The shockwave is focussed into a small area where the stone is causing fragmentation and thus allowing the fragments to pass naturally. Not all stones break up with lithotripsy and thus various different factors should be taken into account such as:

1. Stone size - whilst guidelines suggest stone up to 2cm can be treated, that is often a lot of stone volume, and so often a lower maximum size is favoured

2. Stone location - stones in the bottom of the kidney are less likely to be successful as the fragments do not drain from the kidney

3. Estimation of stone hardness using density of the stone - some stones are known to be hard and if this is known from previous experience, stone analysis or guessed from stone density then ESWL may not be a good choice

4. Depth of the stone from the skin - in larger patients, the kidney sits deeper in the body and away from the skin. This makes targetting the stone more difficult and some of the shockwaves are absorbed by the body tissues

5. Availability - not all hospitals have an ESWL machine, and so may consequently not be offered

6. Patient choice - this is key. Whilst less invasive, ESWL can give more uncertainty, both from overall success, but also in the following few weeks with possibility of stone fragments passing or getting stuck. Thus some patients may prefer a more invasive but more predictable treatment

It is less suitable for patients with single kidneys or those on blood thinning medication. Often 2-3 treatments are given, usually 2 weeks apart. If there is no fragmentation after that time, then alternative treatments are considered.

It is usual to see blood in the urine afterwards and feel a bit bruised and sore. Specific complications include:

1) Pain from a stone passing or getting stuck in the ureter which may require further treatment

2) Infection in the urine. Rarely this can be more severe

3) Bruising or blistering around the skin site

3) Haematoma (blood clot around the kidney). This is rare and usually managed conservatively i.e. resolves by itself, and no further ESWL would be given.