Equine Science Update
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A minimally invasive technique using a laser can be an effective method of treating some urinary calculi in horses, according to a recent report.

Normal equine urine contains many calcium carbonate crystals. Despite that, the formation of stones (“calculi”) in the urinary tract of horses is not common. Calculi can form anywhere in the urinary tract, but are most often seen in the bladder (“urocystoliths”) or urethra (urethroliths”).

Treatment options include surgical removal, which may require general anaesthesia and carry the risk of complications - in particular peritonitis. Other methods include disrupting the calculi with shock waves or laser.

Researchers at the Virginia-Maryland Regional College of Veterinary Medicine and the School of Veterinary Medicine at the University of California, Davis have described a technique using laser lithotripsy directed through a flexible endoscope.
Written by Mark Andrews. Published online 27.04.10
 © Copyright Equine Science Update  2010
Bladder stone laser treatment
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Lasers have been used before to break up urinary calculi. Although it is relatively easy to access the mare’s bladder, it is a more difficult procedure in the gelding because of the length of the urethra. In the past it has been necessary to open into the urethra below the anus to gain access to gelding’s urethra.

But using an endoscope to transmit the laser beam means that the procedure can be carried out without the need for epidural or local analgesia.

An optical fibre is passed through the biopsy channel of the endoscope. This is used to direct the beam from the 20W Holmium: Yttrium Aluminum Garnet laser onto the bladder stone.

The surgeon sweeps the fibre across the surface of the urolith to produce a crater or groove until eventually a fragment breaks off. This process is repeated as many times as necessary until the remaining pieces of urolith are small enough to pass out through the urethra

Larger fragments are removed by grasping them with a wire basket passed through the endoscope. Smaller fragments are flushed out.

The clinicians make sure they can always see the tip of the optical fibre when the laser is activated so as to prevent it coming in contact with the bladder wall and causing accidental damage.

The report, published in the Journal of Veterinary Internal Medicine, carries details of seven cases of urinary calculi that were treated using laser lithotripsy. In all cases the procedure was performed by Dr David C Grant of the Virginia-Maryland Regional College of Veterinary Medicine.

Successful cases took between 101 to 150 minutes to complete.

All uroliths in this series of cases were composed of calcium carbonate.

There were no serious complications directly related to the laser lithotripsy procedure. Two horses had small burns of the inner lining of the bladder. These were superficial, and did not cause detectable signs. On one occasion the tip of the optical fibre broke off and had to be retrieved from within the bladder using forceps passed through the endoscope’s biopsy channel.

The procedure was not successful in two cases. The authors suggest that if no progress is made within the first 30 minutes the case will have to be managed by other means.

“Uroliths in which only small pieces can be dislodged or in which only holes can be made in the surface of the urolith  - are not suitable for management by laser lithotripsy “

The technique was successful for removing all uroliths and fragments in 5 of 7 cases. The authors concluded that laser lithotripsy combined with lavage and retrieval of larger fragments using the endoscope was a safe procedure.

For more details see:

Holmium: YAG Laser lithotripsy for urolithiasis in horses.
DC Grant, JL Westropp, R Shiraki, AL Ruby.
J Vet Intern Med (2009) 23, 1079-1085.