How is the kidney reached?
Under general anaesthetic, a telescope is us
ed to insert a small ureteric catheter from the bladder up to the kidney. This allows dye to be injected into the kidney and prevents stone fragments from falling down the ureter towards the bladder to cause a blockage.
The kidney is then punctured with a needle, using X-ray or ultrasound screening, so that a guidewire can be inserted into the drainage system of the kidney. This guidewire is used to "stretch up" an opening into the kidney, approximately 1cm wide, through which instruments can be inserted to inspect the inside of the kidney (as in the diagram, righ).
How is the stone broken & removed?
Small stones (less than 1cm across) can often be removed intact.
Larger stones need to be broken up using a laser (pictured right), an ultrasonic probe or a vibrating metal probe which breaks the stone like a pneumatic drill.
The larger stone fragments are picked out with forceps and the smaller fragments either wash out during the procedure or are sucked out using the ultrasound probe.
Video - Ultrasound fragmentation of a kidney stone
Features of this video (courtesy of Mr Oliver Wiseman)
- The ureteric catheter (pale blue with dark stripes) at the top of the screen
- The stone (yellow-brown) in the centre of the screen
- The ultrasound probe (silver) at the bottom of the screen
- The guidewire (pale green) seen as the stone fragments are removed with forceps at the end of the video