Durability of working channel in flexible ureteroscopes when inserting ureteroscopic devices.

Purpose: 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. Materials and Methods: 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° to 120°, and each device was inserted and removed 100 times for each selected angle of the channel. Any induced pinholes were idnetified by an air-leak test. Also, the inside of the channel was inspected with an extremely fine fiberscope. Results: 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°. However, the tips of 200- or 250-µm holmium laser fibers shaved the inner surface of the channel at 60° of deflection, and at 120°, the laser fiber either penetrated the channel or could not ...