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Extracorporeal shock wave lithotripsy (ESWL)

Extracorporeal shock wave lithotripsy (ESWL) uses focused sound waves to break kidney or ureter stones into smaller pieces so that they can pass out more easily. It is suitable for stones < 2 cm in size. The success rate depends on the site of the stone and its hardness. The procedure is very safe and does not damage the kidney or surrounding organs.

 

How it is done

ESWL is easily done as an outpatient procedure and takes about 1 hour. The patient lies on a water-filled cushion and the stone localized by means of X-ray or ultrasound. Xray targeting is preferred but if the stone cannot be seen on the xray, then ultrasound localisation method is used. Pethidine analgesia with sedation is injected as 3000 to 4000 shocks of sound waves are needed to shatter the stone.

The patient lies on a water-filled cushion & the stone targetted using the xray unit of the machine

A check xray and ultrasound is done 2 to 4 weeks later to confirm the outcome. Should there be any remnant stone > 5 mm, a second session may be needed.

Dr Chin doing ESWL under xray

 

ultrasound localisation

under ultrasound localisation

Complications include:

  • bloody urine. This occurs for a few days only.
  • colicky pain. As the stone fragments pass out, they cause temporary blockage and pain. The pain can be so bad that the patient may require analgesic injections. Drinking plenty of water will help flush out these small stones.
  • swollen kidney (hydronephrosis). If the stone fragments are still too big, they may get stuck along the lower ureter to cause hydronephrosis. If the swelling does not resolve, and is accompanied by recurrent colic, a double-J stent may need to be inserted to unblock the kidney.
  • urinary tract infection (UTI). This is due to release of bacteria within the stone.
  • kidney haematoma. This is usually small and resolve over a few weeks. Large haematomas can cause loin pain and fever and antibiotics are given to prevent infection of the blood clot.

 

Desired Outcomes:

  • no colic
  • no large haematoma (<3% risk)
  • no UTI
  • stone fragments < 3 mm