Flexible Ureteroscopes: Fiberoptic and Digital

Abstract

Ureteroscopes have undergone a significant evolutionary course in terms of both concept and design. The earliest flexible ureteroscopes were used only for diagnostic purposes. With subsequent addition of working channels, ureteroscopes were used in a more active and therapeutic role. Limitations of semirigid ureteroscopes revealed that an ureteroscope with an articulating/deflecting nature would be required for navigation of more proximal renal and otherwise tortuous anatomy. With smaller caliber and combined deflective mechanisms, currently available flexible ureteroscopes can now generally be advanced into all portions of the kidney and its associated calcyceal anatomy for treatment of a number of pathologies.

A thorough understanding of the construction of the flexible ureteroscope is critical in understanding how to properly use these instruments, in terms of understanding their capabilities, limitations, optimization of use, and their care, as these instruments, due to their small caliber and fragile nature, are prone to damage.

Critical elements for successful construction of modern-day working flexible ureteroscopes include ability to acquire and transmit an image, ability to transmit or produce light sufficient for imaging, functional working channels for use of ancillary devices, adequate channel capacity for irrigation, ability to have active control maneuverability of the scope, and small shaft caliber. Though digital flexible ureteroscopes have a different operative paradigm in terms of optics and image production, many mechanical and structural features of these ureteroscopes remain quite similar to their fiberoptic counterparts.

Despite widespread use, there has been concern that fiberoptic ureteroscopes tend to have a grainy image, water may leak into the lens, and fibers may burn out and fracture, resulting in loss of image quality. The key paradigm change with digital flexible ureteroscopes is the “chip on the tip design,” where an image is picked up, at times processed, and then transmitted by a digital sensor, and sent to a proximal point a single wire, where further processing and transmission take place. This arrangement bypasses the fragile optical fiber system of conventional fiberoptic flexible ureteroscopes.

Though fiberoptic ureteroscopes are being replaced with their digital counterparts, a thorough understanding of these earlier ureteroscopes is important in that studies of these ureteroscopes reveal a number of issues that impact the use and durability of ureteroscopes in a large number of ways. It is likely that such findings will also facilitate improvements in digital flexible ureteroscopes.

Many parameters of flexible ureteroscopes have been compared in a variety of fashions. Review of these investigations lends further understanding into the features and limitations of these ureteroscopes, in terms of working parameters (optical/mechanical) and overall durability. There are few all-inclusive direct comparison studies. Durability studies are of importance in that costs of damage and maintenance factor significantly into overall cost of ureteroscopy. As digital ureteroscopes have only more relatively recently been introduced into more regular use, data regarding outcome with them, using a number of assessment parameters, will be forthcoming in the near future.

Though experience to date with digital flexible ureteroscopes is limited, they have been received quite favorably. They have notably improved image quality, a brighter image, are lightweight, and likely cause less operator-related fatigue. Digital ureteroscopes carry the immediate promise of better optics and visualization, but only further experience will dictate to what degree they address other shortcomings that exist beyond those of optics, namely, in terms of working channel parameters, reliable/user-friendly deflective mechanisms, and durability.