How the Procedure Works
ESWL is a non-invasive procedure that uses focused sound waves to fragment (break up) large kidney stones into smaller pieces so that they can pass down the ureter and in to the bladder.
Extracorporeal means “outside the body” therefore no surgical instruments are used so anaesthetic time is short and recovery time is quick.
Furthermore, the procedure is usually done on an outpatient basis which means no overnight stay is needed and patients usually go home the same day.
An ESWL procedure typically last about an hour. Once the patient is anaesthetised, a water filled cushion which delivers the focused shockwaves, is positioned in contact with the patient’s flank on the side of the stone. A series of up to 3500 focused shock waves are delivered to fragment the stone.
Following the procedure patients usually spend two or three hours in recovery before being sent home where they are encouraged to rest for a day or so. It is also advisable to drink plenty of water for several weeks after the procedure as this will help to flush out any remaining stone fragments.
The soundwave penetrates from the outside through the skin surface and accurately targets the kidney stone. All other treatments are invasive and require a scope to enter the body to find the stone making it a higher risk procedure.
Before treatment commences the Radiographer uses either ultrasound or X-rays to locate the stone within the kidney. Once localisation has been achieved the accurately focused shockwaves (sound/pressure waves) are repetitively directed on to the kidney stone until it begins to weaken and expand and eventually breaks down in to small fragments similar in size to small particles of grit or sand. This process is called fragmentation.
Once stone fragmentation has occurred, which we can usually see on the X-ray or ultrasound, the remnants of the kidney stone will pass out of the kidney, down the ureter, in to the bladder from where they then pass out of the body by the process of urination.
Benefits of Ultrasound Localisation
The primary reason for using ultrasound localisation during a ESWL procedure is that the patient is not exposed to ionising radiation.
Another reason for using ultrasound is that it can identify Radiolucent stones which cannot be seen on X-ray. This allows stones of different compositions including Calcium Oxalate, Calcium phosphate, Uric Acid, Cystine and Struvite to all be targeted successfully.
Furthermore, whilst using ultrasound you have a live image of what is happening in the kidney, changes to the stone size, position and patient respiration can all be monitored and as a result treatment protocols, including duration, intensity and position can be adjusted appropriately to ensure the optimal treatment outcome is obtained.
Although ultrasound should be the modality of choice it does have some limitations. If the stone is in the Pelvic Ureteric Junction (where the kidney attaches to the ureter), it can be more difficult to localise, particularly on large patients. If the stone is in the ureter itself, localisation is not possible.
Benefits of X-Ray Localisation
When ultrasound localisation of the kidney stone is not suitable X-ray localisation can be utilised. The primary benefit of X-ray localisation is that it can identify Radiopaque calculi (visible on X-ray) anywhere within the renal collecting system. Localisation is generally swift and easy to interpret.
However, only Radiopaque calculi can be imaged using this modality, Radiolucent stones cannot be imaged at all.
With our ability to use both ultrasound and X-ray localisation techniques we have greatly enhanced the services we provide to our contracted hospitals.
Over the last 5 years we have been introducing ultrasound localisation to all our hospitals and as a result more that 80% of all procedures carried out by EMU are now ultrasound guided.