Durability of working channel in flexible ureteroscopes when inserting ureteroscopic devices

We studied the physical damage to the working channel of flexible ureteroscopes caused by insertion of various accessories. A procedure was developed to avoid channel damage.

An experimental model representing a flexible ureteroscope was prepared, and damage to its working channel was evaluated by inserting instruments through it. Deflection angles of the channel were changed from 0 degrees to 120 degrees, and each device was inserted and removed 100 times for each selected angle of the channel. Any induced pinholes were identified by an air-leak test. Also, the inside of the channel was inspected with an extremely fine fiberscope.

Insertions of 3F biopsy forceps or a 2.4F Nitinol stone-retrieval device caused only slight damage to the model channel, even when the deflection angle was 120 degrees. However, the tips of 200- or 250-microm holmium laser fibers shaved the inner surface of the channel at 60 degrees of deflection, and at 120 degrees, the laser fiber either penetrated the channel or could not be advanced because of resistance by the channel wall. When the laser fiber was inserted within a protective tube, the channel was never damaged, even when the deflection angle was 120 degrees.

When devices are inserted into the working channel of a flexible ureteroscope, damage to the wall depends on the kind of device and deflection angle. Harm could be avoided by inserting the devices, especially laser probes, within a protective tube.