Trends Toward Miniaturization
One trend that has been a constant in the field of endourology since its founding, and which will be interesting to follow as it relates to the discussion of novel stone management devices in the future, is device miniaturization. In particular, the advent of miniature PCNL – also known as 'mini-PCNL' – techniques and equipment has sparked great debate among thought leaders in the field about the potential risks and benefits of downsizing scope and sheath size to perform 'mini' procedures.[35–37] Of critical importance to the discussion regarding mini procedures is choice of lithotrite and mode of stone evacuation. Since one of the principal advantages of PCNL over ureteroscopy is the ability to ablate and remove large volumes of stone quickly, detractors of mini procedures cite concerns about how this ability might be preserved despite miniaturized equipment.
In anticipation of this trend, the manufacturers of the Shockpulse and Trilogy systems have created smaller diameter probes sizes which are designed to be used with mini-PCNL nephroscopes – 1.83 mm × 418 mm for Shockpulse and 1.5 mm × 440 mm and 1.9 mm × 341 mm for Trilogy. The most commonly used mini-PCNL scopes have outer sheath sizes of 15–18 Fr, scope diameters of 11–12 Fr, and functional working channels of 5–6 Fr. Due to this variation in size specifications, caution is advised when selecting a lithotrite system and/or a mini-PCNL scope set, because while all of the miniature probe sizes are compatible with a 6 Fr working channel, the 1.83 mm and the 1.9 mm probes are not compatible with a 5 Fr (1.66 mm) channel. Furthermore, since the mini probes only come in a single length, there is additional potential for incompatibility between based on probe-working channel length discrepancy. Finally, before recommendation for routine adoption of the mini probes and procedures, additional in-vitro and in-vivo testing of these smaller instruments is warranted. Currently, many proponents of mini-PCNL support the use of new generation high-power lasers to ablate stone during the procedure,[38,39] although this clearly comes at the price of not performing simultaneous suction evacuation of fragments and needing to rely either on manual removal or irrigation flow to achieve reasonable stone-free rates.
Curr Opin Urol. 2020;30(2):144-148. © 2020 Wolters Kluwer Health, Inc.