Key points

Introduction

Over the past 3 decades, endourology has undergone a remarkable evolution with the advent and incorporation of new technologies. The development of smaller, more flexible ureteroscopes, higher-definition cameras, and a wide variety of novel instruments have changed the role of the field from one of diagnostics to one of treatment. In this review, the authors highlight the latest technologic achievements in ureteroscopy.

Introduction

Over the past 3 decades, endourology has undergone a remarkable evolution with the advent and incorporation of new technologies. The development of smaller, more flexible ureteroscopes, higher-definition cameras, and a wide variety of novel instruments have changed the role of the field from one of diagnostics to one of treatment. In this review, the authors highlight the latest technologic achievements in ureteroscopy.

Flexible ureteroscopes

Advancements in flexible ureteroscopes have had perhaps the greatest impact in changing endourology. Smaller sizes and increased capabilities in terms of optics, deflection, and instrumentation have now made it possible to access the entirety of the urinary tract. The rate of technologic improvement in this field has been staggering, with new ureteroscopes introduced each year ( Table 1 ). Representations of the deflection characteristics and tip appearances of some of the newer flexible ureteroscopes can be seen in Figs. 1 and 2 .

Deflection characteristics of currently available flexible ureteroscopes.

( From Traxer O. Digital and video flexible ureterorenoscopes: the future is now. AUA News 2012;17(7):1–9; with permission.)

Distal tips of currently available flexible ureteroscopes.

( From Traxer O. Digital and video flexible ureterorenoscopes: the future is now. AUA News 2012;17(7):1–9; with permission.)

One of the most significant changes has been a change from fiberoptic to digital imaging. This change has been made possible through the advancement and miniaturization of the charge couple device and complementary metal oxide semiconductor image sensors. These chips are now small enough to be directly incorporated at the tip of the ureteroscope creating the so-called chip on the stick scope. Such technology eliminates the need for internal optics within the shaft of the scope potentially allowing for more durable deflection mechanisms and equipment overall. An additional advantage is eliminating the need for several pieces of equipment, including a separate camera; camera cord; light source or light cord; and several cumbersome steps, such as focusing and white balancing. Furthermore, without the need for fiberoptic bundles within the shaft, larger working channels can be used. Although promising, the improvements do come at the expense of a larger-tip diameter, generally 8F or greater, making passage into narrow areas slightly more challenging. Additionally, the use of these scopes occasionally requires prestenting the ureter, ureteral balloon dilation, or the concomitant use of a ureteral access sheath to obtain access.

The image obtained with a digital scope is generally larger and clearer than that obtained with traditional fiberoptic scopes. Additionally, there is no honeycomb/pixelation pattern (Moiré effect) on the screen ( Fig. 3 ). The first flexible digital ureteroscope was introduced in 2007. This scope, the DUR-D (Gyrus ACMI, Southborough, Massachusetts) has been estimated to have an increased image size up to 150% larger than its fiberoptic counterparts. When compared with the Storz Flex X ² (Karl Storz, Tuttlingen, Germany) fiberoptic flexible ureteroscope, it was associated with a faster stone fragmentation rate and corresponding decrease in total operative time. The next digital scope to be introduced was the Olympus URF-V (Olympus Corporation, Tokyo, Japan) flexible digital ureteroscope in 2008. When compared with its fiberoptic counterpart, the Olympus URF-P5, it was found to have a higher resolution at a variety of distances and created an image size 5.3 times as large. Multescu and colleagues also compared this scope with the Storz Flex X flexible fiberoptic ureteroscope, and they found that the digital scope had more difficulty accessing narrow infundibula 4 mm or less in width. They did, however, find the digital scope to be superior in terms of visibility, maneuverability, and loss of deflection after repeated use. The most recent of the flexible digital ureteroscopes is the Storz Flex-Xc, which is the smallest digital ureteroscope on the market at 8.5F but has not yet been compared with a fiberoptic counterpart. It is not available in the United States at the time of this article; however, it is being used in several European countries.

Comparison of conventional fiberoptic ureteroscopic image ( A ) versus digital ureteroscopic image using URF-V ( B ). (Olympus Corporation, Tokyo, Japan).

Although these newer digital scopes are more expensive than their fiberoptic predecessors, proposed improvements in durability may ultimately offset differences in price. Knudsen and colleagues analyzed scope durability among 4 of the most recent fiberoptic flexible ureteroscopes and found a mean range of 5.3 to 18.0 cases until the need for repair. With typical repair costs estimated between $3000 and $6000, the need for improved durability cannot be overemphasized. Further comparative studies as well as cost analyses will likely play a large role in the future adoption of these scopes.

Semirigid ureteroscopes

Semirigid ureteroscopes ( Table 2 ) have had a slower evolution in terms of technologic improvement relative to flexible ureteroscopes but remain the most commonly used type of scope for access to the upper urinary tract. Unlike in flexible ureteroscopy, the transition to digital scopes has been much slower among their semirigid counterparts. One possible reason to explain this slower adoption is the fact that the rigid shaft design allows for an increased density of fiberoptic bundles, which in turn allows for decreased image degradation Currently there is only one major manufacturer of ureteroscopes that sells a digital semirigid instrument, the Olympus Pro Video scope (also known as the EndoEye ureteroscope). Image properties obtained with a digital scope are favorable. One previous study found that the image size was approximately 2.5 times greater with a digital semirigid scope. One downside, however, is that the current tip diameter is relatively large (8.5F/9.9F) compared with the fiberoptic versions. Multescu and colleagues examined the performance of the Olympus EndoEYE compared with a traditional fiberoptic semirigid ureteroscope and graded visibility and maneuverability on a 5-point scale after each case that it was used. Overall, the digital scope had improved visibility (4.5 vs 3.5) but poorer maneuverability (3.93 vs 4.57) when the patient was not prestented. Furthermore, there was a lower success rate without prestenting among the cases where the digital scope was used (84% vs 98%). Decreasing the diameter of the scope is, thus, the logical next step in the evolution of this equipment and will likely be the rate-limiting step before widespread adoption of this technology is seen.

Advanced image settings

The introduction of high-definition cameras and video has brought visualization capabilities in ureteroscopy to an all-time high; however, there are several other advanced imaging technologies on the horizon. One is the use of narrow band imaging (NBI). NBI, developed by Olympus, is proposed to facilitate the detection of urothelial tumors. This technology works by enhancing the color contrast of increased vascular patterns caused by angiogenesis in tumor formation. In NBI, two wavelengths of light, 415 nm (blue) and 540 nm (green), are used to illuminate tissue. These wavelengths of light are strongly absorbed by hemoglobin, making tissue with increased vascularity (tumors) appear dark relative to surrounding normal mucosa ( Fig. 4 ). Currently, the only ureteroscope to offer such capabilities is the Olympus URF-V. To date, only one published study has investigated the clinical utility of using NBI in the diagnosis of upper tract urothelial carcinoma, though results were promising with an improved tumor detection relative to white light imaging by approximately 23%.

Appearance of upper tract urothelial tumor during digital ureteroscopy using conventional white light ( A ) and Narrow-Band Imaging ( B ).

( From Traxer O, Geavlete B, de Medina SG, et al. Narrowband imaging digital flexible ureteroscopy in detection of upper urinary tract transitional-cell carcinoma: initial experience. J Endourol 2011;25(1):19–23; with permission).

Another advancement to expect in the next several years is the application of 3-dimensional technology. The use of 3-dimensional vision has been shown to enhance surgeon performance in laparoscopic and robotic settings, and the application to endoscopy would be a logical next step.

Virtual endoscopy is yet another technology that is currently being developed. The idea for this is that the combination of ureteroscopy and computer-engineered software might help construct a reliable, 3-dimensional image of the ureteral anatomy. This technology might help identify tumors and could play a useful role in the surveillance of upper tract urothelial carcinomas; however, this technology is currently in its early infancy.

Finally, in 2011, a pilot study was performed demonstrating the use and efficacy of robotic flexible ureteroscopy. This platform was converted from a robotic console designed for intracardiac applications but modified for use in ureteroscopy ( Fig. 5 ). Eighteen patients were successfully treated with this method. Benefits mentioned by the investigators included the ergonomic advantage of being seated and using the robotic console as well as the ability to scale and fine tune motion to a very small degree based on stone fragment size. Disadvantages included the large size of the robotic sheath (14F), which required prestenting in all cases, and the procedure being quite cumbersome in its infancy. Time will tell whether there is a role and benefit to this technique.

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