Hazards make finding the right laser sheath critical

Amsterdam, Netherlands-A protective polyamide laser sheath for use during flexible ureteroscopy and laser lithotripsy showed little effect on deflection characteristics but markedly impaired irrigation flow in a new study from Canada.

Researchers measured the deflection angles for each scope using a protractor. They administered irrigant flow with a constant pressure infusion pump and measured it by the volume of fluid administered in 1 minute.

Fiber requires caution

Although technical advances have greatly improved the functionality and durability of flexible fiber optic ureteroscopes, they remain fragile instruments, Dr. Razvi pointed out, and working channel damage is not uncommon.

"The most frequent cause of ureteroscope damage in over 40% of cases at our high-volume endourology center is to the working channel, with damage to other components of the ureteroscope (eg, angulation wires, outer core, lens, defection cover) following. Virtually all sources of damage to the working channel are due to the laser," he said.

Urologists attending Dr. Razvi's presentation at the World Congress on Endourology were curious as to the choice of material selected for the sheath. Some asked whether other materials might work better. Others believed that material was less of an issue than were the mechanical properties of the working channel.

"Polyamide was readily available and was relatively laser resistant. The study showed us that maybe we should think about other strategies or other types of materials," Dr. Razvi said. "In terms of the mechanical effects of the sheath, however, it did not significantly affect deflectibility, but definitely did affect irrigation flow."

He described the use of small-diameter catheters as a possible method of protecting the working channel and reducing the potential for laser fiber damage. With most flexible uteroscope working channels in the 3F to 4F size range, identifying a protective sheath that will not significantly impair irrigant flow or reduce deflectibility remains the challenge, he said.