Digital flexible ureteroscopes are widely used in clinical practice and stand out because of their enhanced high‐quality images. Previous ureteroscopes transmitted images via fiber‐optic cables, with an external light source and an attached camera. Today’s digital ureteroscopes do not necessitate such bulky devices; instead, digital images are transferred to a screen via a single cable (Figure 42.1). This feature reduces the effort required by the surgeon, and better quality images make the operation easier to perform. Pixel resolution of digital ureteroscopes is nearly ten times better than that of fiber‐optic ureteroscopes and the images can be magnified digitally and viewed during the operation (Figure 42.2). ACMI DUR‐D Invisio was the first digital flexible ureteroscope introduced for urologic practice. It contained a complementary metal oxide semiconductor (CMOS)‐based chip at its distal end. Even though ACMI DUR‐D had better image resolution than previous ureteroscopes, there were some disadvantages, such as increased instrument diameter. This sometimes prevented the surgeon from reaching the desired lower calyx and produced a deteriorated image when the red laser beam was activated. Technological advancements have led to the production of newer and better quality digital ureteroscopes. The Olympus URF‐V, which contains a charge‐coupled device (CCD)‐based chip, and the Karl Storz Flex‐Xc, which contains a CMOS‐based chip, were introduced in the following years.

Better contrast discrimination, color differentiation, and higher‐resolution images obtained by digital ureteroscopes lead to better diagnosis of millimetric lesions and increased comfort for the surgeon during renal stone fragmentation. Focusing on the stone and identifying the calyceal anatomy is much easier with these ureteroscopes, which leads to decreased risk of mucosal injury and bleeding during stone fragmentation with a holmium laser (Figure 42.3). Enhanced imaging achieved by digital ureteroscopes also decreases the operation time when compared with fiber‐optic ureteroscopes [1].

Although technological advancements have led to better quality images and more durable ureteroscopes, there are still certain problems owing to the fragile nature of these instruments. Many studies have compared the durability of digital ureteroscopes with fiber‐optic ureteroscopes and have proven that digital ureteroscopes are more durable. However, flexible ureteroscopes are all fragile instruments. Repetitive use of these instruments eventually decreases the angle of maximal deflection. Proper handling of the instruments by experienced surgeons significantly increases their durability. Use of an access sheath during the introduction of the instrument into the upper urinary tract also increases its life span. Avoidance of maximal deflection and relocating stones before fragmentation are also beneficial precautions. Another problem with these instruments is possible damage to the digital chip and ureteroscope by the holmium laser if unintentionally retracted into the instrument during stone fragmentation. Turning the laser off while retracting it into the ureteroscope or fixing the laser after appropriate placement are possible precautions, but they are not guaranteed. Use of an “endoscope protection system” (EPS) is a better option. When the laser is retracted into the instrument, and therefore disappears from sight of the CMOS‐based chip, the EPS recognizes the absence of the blue cladding of the active laser fiber and automatically switches it off. All of these precautions lead to increased life span of these expensive instruments and reduce repair costs.

Digital ureteroscopes have become the subject of many studies. Newly introduced “chip on the tip” technology, superior imaging quality, newly introduced working channels, and maneuverability abilities are the main features that have been evaluated. Binbay et al. and Somani et al. made a comparison between digital and conventional ureteroscopes, discussing the slightly limited maneuverability and shorter operation times of digital scopes [1, 2]. Shah et al. compared the ACMI DUR‐D with the Olympus URF‐V and found better visibility and maneuverability of the CCD‐based Olympus URF‐V [3]. Lusch et al. compared the performance and characteristics of the dual‐channel Wolf Cobra fiber‐optic ureteroscope with two single‐channel fiber‐optic ureteroscopes and a single‐channel URF‐V digital ureteroscope. They found better image resolution with the URF‐V owing to its digital sensor chip and increased irrigation flow of the Wolf Cobra as a result of its separate working channel. They also noted the increased thickness of the Wolf Cobra when compared with other ureteroscopes [4]. Richard Wolf has since introduced a digital version of this unique instrument called Cobra Vision. Technical details of available digital ureteroscopes are listed in Table 42.1.

Humphreys et al. [5] published a unique article about the use of these novel digital ureteroscopes. They conducted this study using the ACMI DUR‐D digital ureteroscope and mentioned the possible use of these instruments, which produce high‐quality images, in detecting the early stages of calcium oxalate stone formation and possibly understanding the mechanism of stone formation [5]. Multescu et al. compared the Flex‐Xc, URF‐Vo, and Wolf Cobra in terms of maneuverability, imaging, and deflection mechanisms. They stated that the most important difference was image quality, but another important difference was the more effective irrigation flow of the Wolf Cobra [6]

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