Normal equine urine contains many calcium carbonate crystals. Despite that, it is not common for stones (“calculi”) to form in the urinary tract of horses. They are most often seen in the bladder (“urocystoliths”) or urethra (urethroliths”).
It is possible to remove them surgically, 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 minimally invasive technique using a laser to break up the urinary calculi.
An optical fibre is passed through the biopsy channel of the endoscope. This is used to direct the beam from the laser onto the bladder stone. The procedure can be carried out without the need for epidural or local analgesia.
The surgeon sweeps the fibre across the surface of the stone 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 technique was successful for removing all uroliths and fragments in five of a series of seven cases. The authors concluded that laser lithotripsy combined with lavage and retrieval of larger fragments using the endoscope was a safe procedure. They suggest that if no progress is made within the first 30 minutes the case will have to be managed by other means.
Read more at Equine Science Update