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Urolithiasis https://doi.org/10.1007/s00240-018-1086-2

REVIEW

Vision for the future on urolithiasis: research, management, education and training—some personal views

A. Rodgers1,5 · A. Trinchieri2,5 · M. H. Ather3,5 · N. Buchholz4,5 · On behalf of the U-Merge Scientific Office

Received: 18 September 2018 / Accepted: 23 October 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018

AbstractThe field of urolithiasis has undergone many rapid changes in the last 3 decades. In this article, three eminent experts in various fields of urolithiasis research describe their respective visions for the future in stone research, stone treatment and surgical training. Many stone researchers have seen and regretted that there has not been a real breakthrough for decades now. Exceptions are the application of citrate prophylaxis and the abandonment of calcium-avoiding diet in stone formers. Certain areas of stone research have been exhausted and the body of literature available should suffice as background knowledge in those. Yet, to find meaningful mechanisms of clinically applicable stone prevention, the limited funds which are currently available should be used to research priority areas, of which crystal–cell interaction is envisioned by one of the present authors as being a crucial direction in future stone research. In the opinion of the second author, surgical stone treatment is very much technology-driven. This applies to the evolution of existing technologies and instruments. In addition, robotics, IT and communication software, and artificial intelligence are promising and are steadily making a meaningful impact in medicine in general, and endourology in particular. Finally, the third author believes that despite the exciting advances in technology, the role of the surgeon can never be replaced. The idea of a fully automated, artificially thinking and robotically performing system treating patients medically and surgically will not appeal to urologists or patients but may at least be a partial reality. His vision therefore is that surgical training will have to take on a new dimension, away from the patient and towards virtual reality, until the skill set is acceptably developed.

Keywords Urolithiasis · Research · Managment · Training · Education · Vision · Future

Introduction (NB)

My introduction to stones coincided with the application of the first extracorporeal lithotripters some 30 years ago. As a young resident, I was present when fully anaesthetised patients were carefully hoisted into the shockwave lithotrip-er’s bath tub, when the first ureteroscopy was performed in our clinic with a fully rigid F14 scope, and when the first percutaneous nephrolithotomy was performed by an experienced urologist who just had brought back this novel technique from the USA. Stone research was then focussed on epidemiology and promoters and inhibitors of stone for-mation. Patients were advised to avoid calcium. Open stone surgeries were still regularly performed.

I and many urologists of my generation have witnessed a rapid and often turbulent development in the stone field over the last 30 years, from open surgery to micro-PCNL, from knife to robot, from “try one, do one, teach one” to virtual

U-merge Ltd. (Urology in Emerging Countries) is an academic urological platform dedicated to facilitate knowledge transfer in urology on all levels from developed to emerging countries. U-merge Ltd. is registered with the Companies House in London/ UK.

* N. Buchholz noor.buchholz@gmail.com; u-merge@u-merge.com

1 Department of Chemistry, University of Cape Town, Cape Town, South Africa

2 Department of Urology, Manzoni Hospital, Lecco, Italy3 Department of Urology, The Aga Khan University Hospital,

Karachi, Pakistan4 Sobeh’s Vascular and Medical Centre, Dubai, UAE5 U-merge Ltd, London, UK

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reality training, from diet trials to sophisticated intra-tubular computer modelling.

We have experienced those changes first-hand, and are perhaps best suited to give a vision of the future as we see it, based on the developments of the past, recent advances, and past failures.

I therefore invited three long standing experts in their fields to elaborate on their visions for the foreseeable future on three cornerstones of urolithiasis, namely stone research (AR), surgical stone management (AT), and education and training of stone surgeons (HA).

Stone research (AR)

My vision for future research on the pathogenesis and con-servative management of stone disease involves identifica-tion of the top priority in these fields and to apply basic science resources to investigate this priority exhaustively. An obvious starting point is to review the successes and failures of the initiatives of the past 40–50 years. Consid-eration of the most recent surveys on stone recurrence and incidence paints a dismal picture of worldwide increases in these statistics (Table 1) [1–4]. As such, the only conclu-sion which can be drawn is that despite the great efforts of stone researchers over many years, their focus needs to change. In the following discussion, research areas which in the author’s view have been exhausted and no longer warrant ongoing attention will be presented. These will be designated as low priority. Other areas which are deemed as deserving of a relatively more important status will be designated as having medium priority. Ultimately, the top priority will be identified.

Low priority research areas

Epidemiology

Many excellent epidemiological studies on stone disease have been published [1–8]. These have identified the impor-tant factors which influence stone formation. It is not neces-sary to list them here, but it is useful to appreciate that there is an intimate synergism between many of them (Fig. 1). In

many cases, researchers have concluded their reports with statements about epidemiological studies having the poten-tial to provide important insights into stone formation. That may indeed have been true, but it is no longer necessary (or interesting) for large scale studies to confirm what we already know—namely that stone disease is more common in males than in females; that populations in hot arid regions are at risk; that a sedentary occupation is another risk fac-tor; that life style plays a role; that oxalate-rich foods should be avoided; and that dietary restriction of calcium is not advised. The objective reality is that all of these factors have been repeatedly confirmed in numerous studies and are all very well-established. As such, further observational studies of this kind are not a top priority for future research.

Stone composition, structure and ultrastructure

Numerous large scale studies from different parts of the world have been published on stone composition (Table 2) [9–14]. These have repeatedly demonstrated that the most common stone-types are calcium oxalate, calcium phosphate and uric acid. Researchers claim that stone compositional studies provide clinical insights into stone management strategies. As before, this is certainly true. Consequently, and appropriately, compositional analysis of stones is widely practiced in the clinical work up of stone patients. But it is important to distinguish between routine procedures and research. As with epidemiological factors mentioned in the

Table 1 Epidemiological studies of stone incidence and prevalence during different time periods

Period Country Prevalence (%) Incidence (%) % Increase References

1965 vs 2005 Japan – 0.054 vs 0.114 111.1 Yasui et al. [1]1976 vs 1994 USA 3.8 vs 5.2 – 36.8 Stamatelou et al. [2]1979 vs 2001 Germany 4.0 vs 4.7 17.5 Hesse et al. [3]

0.54 vs 1.47 172.21986 vs 1998 Italy 5.9 vs 9.0 52.5 Trinchieri et al. [4]

Fig. 1 Epidemiological synergism

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preceding paragraph, this area of investigation has been exhausted and does not rate as a top research priority.

Medium priority research areas

Modulators of urinary saturation

Modulators, irrespective of their mode of action, need to satisfy two main criteria in order for them to be of thera-peutic or prophylactic value in human stone disease. First, they need be absorbable and second, they need to be physi-ologically tolerable. As such, compounds which have dem-onstrated modulatory effects in laboratory experiments but do not meet the criteria for human consumption are of little value and should not continue in future research endeavours.

It is indisputable that urinary saturation leads to crystal formation of stone-forming salts and that stones cannot form without crystals. Investigation of such modulators has been conducted for many years and must continue. However, the harsh reality is that success in this area has been extremely limited. Indeed, citrate is the only example which stands out in this regard. Because of the numerous studies which have demonstrated this substance’s efficacy, several pharma-ceutical preparations containing citrate have been developed and enjoy a large measure of success. Further trials to test their efficacy (and those of other similar citrate-containing

preparations) are no longer a high research priority. How-ever, searching for other non-citrate chelators of calcium and oxalate should continue. Several such substances have indeed been tested (Table 3a) [15–17], but given that these have enjoyed only limited success and that the list of poten-tial chelators is probably nearly exhausted, this research area should be considered as being only of moderate priority.

Modulators of crystal aggregation

Aggregation has been identified as the crucial factor which slows down the rate of crystal passage through the nephron, thereby contributing to particle retention [18, 19]. Besides a few low molecular weight inhibitors, various endogenous urinary macromolecules have been shown to possess this ability (Table 3b) [15–17]. These studies have demonstrated that their efficacy in this regard depends on physiological and structural factors which include expression, urine envi-ronment, defects (chemical, structural, conformational), degree of phosphorylation and sialylation, and extent of self-aggregation. Future research which attempts to identify interventions (dietary and/or pharmaceutical) which opti-mize these parameters is necessary and is regarded as being a moderate research priority.

High priority research area

Modulators of crystal–cell adhesion

Since urinary supersaturation and crystal aggregation occur commonly in persons who do not form stones [20], it seems that the actual transformation of crystals to stones per se should be the main priority of future research (Fig. 2). While particle retention (flow rate of crystals < flow rate of urine) [18] is certainly an important factor, it is fixation of these particles to urothelial cells which allows them to be bathed in saturated urine for periods which are of sufficient duration

Table 2 Stone composition

Country Number of stones References

USA > 10,000 Herring [9]Canada 15,624 Gault et al. [10]France 50,235 Daudon et al. [11]Germany > 200,000 Knoll et al. [12]China 5248 Sun et al. [13]Spain 7949 Millan et al. [14]

Table 3 Modulators [17–19] (a) Supersaturation (LP) (b) Aggregation (MP) (c) Crystal–cell adhesion (TP)

Magnesium Magnesium OsteopontinCitrate Pyrophosphate Inter-alpha-inhibitorPyrophosphate Citrate BikuninBiphosphonate Chondroitin sulphate FibronectinPhytic acid Heparan sulphate Heparan sulphate

Tamm–Horsfall glycoprotein Tamm–Horsfall glycoproteinOsteopontin Chondroitin sulphate AProthrombin fragment 1 Chondroitin sulphate BNephrocalcinUrinary prothrombin fragment 1Inter-alpha-inhibitor

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to promote crystal growth and aggregation, and conversion to stone. Indeed, Khan has stated “one of the approaches to prevent stone formation would be to stop crystal reten-tion. If crystals are not retained in the kidney, there will be no kidney stones” [21]. Like modulators of crystal aggrega-tion, sophisticated laboratory experiments have identified specific UMMs which interfere with crystal–cell attachment processes (Table 3c). Not surprisingly, modulation has been found to be dependent on the nature of the cell and crystal surfaces. In recent years, Randall’s plaque has emerged as a key platform on which crystals can be converted to stones [22]. Sheng et al. have stated that adhesion of functional groups to calcium oxalate crystal surfaces provides the path-way toward a better understanding of kidney stone disease and the eventual design of therapeutic agents [23], while Sakhaee has stated that the development of novel drugs to prevent formation of Randall’s plaque and renal tubular crys-tal adhesion needs to be targeted [24].

It is important to emphasize that identification of crys-tal–cell adhesion as the highest priority area for future stone research is the personal perspective of the present author. In expressing this opinion, recognition of other important mechanisms is appropriate. These include mechanisms which involve the fundamental role of calcium phosphate (CaP) in CaOx stone formation [25] as well as its role in this regard in intratubular and interstitial deposits [26]. In addition, the importance of specific risk periods of crystal-lization including intratubular levels of supersaturation with CaP as well as with CaOx [27] or pH-levels [28] need to be recognised.

Vision for future stone research

In summary, the author’s personal vision of future research into the pathogenesis and treatment of stone disease is to adopt as a priority, investigation of mechanisms by which one of the key steps in stone formation—conversion of crys-tals to stone via adhesion of such crystals to cells—can be blocked. However, this opinion needs to be tempered with recognition that free and unrestricted research without spe-cific boundaries has been most fruitful in the past and that

the proverbial placing of all eggs in one basket might not be the best strategy as we approach stone research in the future.

Surgical stone management (AT)

Since the end of the nineteenth century, technology has begun to have an increasingly significant impact on the diagnostics and treatment of all diseases. In particular, over the last 40 years, technological innovations have revolution-ized the surgical treatment of urinary stones, considering that in the late 1970s of the past century the great majority of urinary calculi was still treated with open surgical pro-cedures. Starting from the 1980s, the use of new methods of extracorporeal and intracorporeal lithotripsy and of new endoscopic instruments to explore the upper urinary tract completely modified the treatment of urinary stones. During the following years, other new technologies were introduced that allowed the continuation of the improvement process that is still ongoing. New technological innovations, espe-cially in the fields of computer science and robotics, will be added in the near future to continue this incredible process of improvement. In the following discussion, I will list the latest developments in various fields of stone treatment, all of which are under further development to be refined and clinically more applicable.

Endoscopy

Advances in endoscopes and other instruments allowed urol-ogists to introduce ureteroscopy and percutaneous nephro-lithotomy techniques since the 1970s. Further innovations involved the subsequent development of more efficient and resistant endoscopic instruments. This process is still ongo-ing and produces innovative new medical instruments and devices every year. Significant improvements have been related to the miniaturization of instruments and the devel-opment of digital camera systems based on Charge-Coupled Devices (CCD) and Complementary Metal Oxide-Super-conductors (CMOS) technology. These innovations made it possible to build flexible ureteroscopes with better image quality and wider working channels to increase irrigation capacity and facilitate instrument passage. I envision that further improvements of digital-HD-video-technology with post-processing software (NBI/SPIES) will provide better resolution and will increase the optical field, and will help with the further miniaturization of endoscopes.

At the same time, the evolution of percutaneous nephro-lithotomy has turned towards an increasing miniaturization of the instruments in association with the use of laser fibres, and more efficient and better designed irrigation and suction systems.

Fig. 2 The critical step in stone formation: conversion of crystals into stones

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The percutaneous nephrolithotomy is now classified as standard (20–22F), mini (16–18F), ultra/super-mini (12–14F), and micro (8–10F).

In the foreseeable future, I envision that these instru-ments will become more robust and less expensive. There is a recent trend towards disposable scopes which have the potential to fulfil these requirements. It remains to be seen how the market forces will adopt this new trend.

Lithotripsy

Extracorporeal shock wave lithotripsy (SWL)

Extracorporeal shock wave lithotripsy (SWL) has revolu-tionized the treatment of kidney stones and has met with extraordinary success worldwide, but the development of its technology has had some unexpected results. We have moved from lithotripters that had a high efficiency in stone fragmentation but required anaesthesia to machines that can be used on outpatients without anaesthesia, but with less efficiency to fragment stones. This evolution, in association with the progress of digital endoscopy, is causing a slow but progressive decline in the use of this method.

The industry tries to counteract this trend with new tech-nological innovations such as the use of a dual electrohy-draulic system, double-layer arrangement of piezo-electric elements, adaptation of the focus to the stone, and the use of broad-focus low-pressure lithotripters [29]. The use of different fluid media could also significantly improve frag-mentation [30].

Intracorporeal lithotripsy

Intracorporeal lithotripsy is based on different sources of energy: electrohydraulic lithotripsy was popularized in 1967, ultrasound was first applied for the destruction of renal stones in 1977, the development of laser for the frag-mentation of ureteral calculi was initiated in 1986, and the first pneumatic device for stone fragmentation was designed in 1992. With advances in laser fibres and power genera-tion systems, laser lithotripsy emerged as the treatment of choice for ureteral stones. Modern high-powered Holmium laser systems provide a wide range of settings, such as pulse energy, frequency, and pulse length. The manipulation of these variables in different combinations allows to have spe-cific effects of stone fragmentation or pulverization (dust-ing), and to reduce stone retropulsion [31].

Stone retrieval devices

The complete removal of stone fragments after lithotripsy has gained importance in endoscopic stone treatment. For this reason, new baskets and graspers continue to be

developed with new designs and smaller calibres. At the same time, devices have been introduced to facilitate the evacuation of calculi with hydrodynamic mechanisms (active/passive washout, purging, vacuum-cleaner-effect). Small fragments can be incorporated in gels or glue-clots to prevent retropulsion and to facilitate their extraction [32].

Robots, robotic arms and tracking systems

Robotics

Robotics is increasingly successful in the surgical treatment of renal and prostatic cancer. The surgical Da Vinci® sys-tem is now widespread throughout the world. New surgi-cal robot systems are currently under development by big companies (Google, Cambridge Consultants, etc.) and will be introduced in the market in the coming years. The Da Vinci® robotic system has also contributed in improving the outcomes of minimally invasive procedures in certain specific and complex stone cases such as simultaneous pyeloplasty–pyelolithotomy, complex pyelolithotomy, and stone removal with simultaneous partial nephrectomy. For endourological procedures, such as ureteroscopy and per-cutaneous nephrolithotomy, specifically designed robots will have to be developed. In fact these procedures, while using sophisticated technological tools, are still based on the operator’s experience and manual dexterity that require a long training period. For ureteroscopy, a specific robot has already been developed to improve the ergonomics of the procedure (Avicenna Roboflex) [33]. Uptake by clinicians of this technology has been slow though and it needs further refinement.

For percutaneous nephrolithotomy, undoubtedly the access is the most challenging part for most clinicians. Therefore, technological innovations have been directed towards the facilitation of targeting and access, whilst reduc-ing X-ray exposure for both, the patient and the surgeon. Currently, access to the renal cavities is performed manually under fluoroscopic or ultrasound guidance. The use of fluor-oscopy inevitably incurs radiation exposure while the use of ultrasound may be challenging due to the difficulty to visual-ize the needle tract. Devices have initially been developed to stabilize the needle position during the targeting process, and in some cases to advance the needle, to minimize direct radiation exposure to the surgeon’s hands. A metal arm with 6 grades of freedom (GoF) movement was developed by Stoianovici et al. to be manipulated mechanically by the urologist, while attached to the side rail of the operating table [34]. A similar “locator” was described by Lazarus and Williams [35] based on an adjustable lockable multidi-rectional head, fixed to the operating table, holding a metal guide that facilitates renal collecting system puncture under fluoroscopy by achieving a precise and fixed alignment.

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Recently, a Mini Access Guide (MAG) was proposed as a cost-effective, portable, and simple alternative to its heavier and costlier predecessors [36].

However, using these devices the surgeon still needs to calculate and plan the needle trajectory to the desired renal calyx.

A low-cost guiding device has been developed to adjust the inclination of the needle based on the computer pro-cessing of fluoroscopic images obtained by means of a C-arm positioned with two different inclinations (0° and 20°). A laptop computer with a specific software and graphic user interface provides the angles to be set on the three axes of the gantry to direct the needle to the targeted calix [37].

The puncture of the calix under ultrasound guidance may also be facilitated by superimposing the images acquired previously with fluoroscopy, CT scan or MRI over the ultra-sound image acquired in real time by the operator. Use of ultrasound with a magnetic field-based navigation system can help to visualize the position of the needle tract in rela-tion to the target calix [38].

Mozer et al. superimposed ultrasound images onto fluoro-scopic images to help plan percutaneous renal puncture [39].

My vision is that the ultimate goal would be to design a fully automated robot to manage all aspects of percutaneous access: planning the needle trajectory, needle positioning and advancement with real-time needle tracking.

Prototypes have been built, but until now their size and complexity have prevented application in routine clinical practice.

The Johns Hopkins Urobotics laboratory has accumulated great experience in this field by producing different versions of devices to assist the surgeon in creating the renal percu-taneous access.

From the original passive robotic arm under guidance of a fluoroscopic C-arm [40], the design was improved by add-ing an electronic needle insertion device and the ability to position the needle by remote control. PAKY (Percutaneous Access to the Kidney) and PAKY-RCM (Remote Control of Motion) allow the needle positioning in the skin puncturing site and the execution of its insertion under control of the surgeon via a joystick [41, 42].

The AcuBot robot combined the original PAKY nee-dle driver with a remote centre of motion and a computer-assisted navigation system that allowed the alignment of the puncture needle in real time by corresponding to a three-dimensional model acquired from preoperative com-puted tomography images. After the preoperative imaging is obtained and reconstructed, markers are placed on both, the patient’s body and the surgical tool to spatially local-ize the needle in relation to the desired target. AcuBot is a multifunctional device that was also successfully tested for percutaneous access to renal cavities [43].

Finally, the MrBot robot has been developed to be used in association with a magnetic resonance imaging system [44]. This system employs a new generation of pneumatic step-per motors using nonmagnetic and dielectric materials for compatibility with a magnetic resonance scanner. This robot has been designed for magnetic resonance-guided access of the prostate gland, but could also be used for percutane-ous renal puncture to avoid ionizing radiation. The last gen-eration of robots showed a precision of 0.72–0.36 mm in in vitro assays.

The results of another system, the Automated Needle Tar-geting with X-ray (ANT-X) were recently presented. The system uses an image registration software with a closed loop feedback system to auto-align the puncture needle to the desired calyx using the bullseye technique [45].

CT‑like imaging with C‑arms

The Uro Dyna-CT (Siemens Healthcare Solutions, Erlangen, Germany) was developed to provide CT-like images in the endourological operating room, in addition to working as a digital fluoroscopy. DynaCT enables to create soft tissue images based on the principles of CT by means of a flat detector (FD) technology. Clinical images, comparable to those generated by a CT scanner, can display organs and vessels. Slice images can be generated by rotating the C-arm of the system in a circle about the patient and performing the requested number of acquisitions that are reconstructed in the same manner as with a CT system. The system supported by a laser-guiding system was used to perform percutaneous complex puncture of the renal cavities [46, 47].

Electromagnetic tracking

Huber et al. [48] experimented with an electromagnetic tracking system for navigated renal access in a porcine ex vivo model. A small electromagnetic tracking sensor was placed into the desired puncture site via a ureteral catheter to guide the surgical needle from the skin puncture site toward the collecting system in a “rendezvous” approach.

Telesurgery

The availability of robots capable of performing more or less complex surgical manoeuvres is the prerequisite for the development of telesurgery. An experienced surgeon can drive the robot’s movements remotely, thus allowing the procedure to be performed in a location where the specific treatment experience is lacking. Remote percutaneous renal access using an automated telesurgical robotic system has been successfully performed [49].

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Augmented reality

The use of a 360° cameras for virtual reality has been used for the transmission of surgical interventions for educational purposes through dedicated websites or apps, allowing stu-dents to virtually be in the operatory room using virtual real-ity goggles Augmented reality is a fusion of projected com-puter-generated images and real environment in real-time via dedicated hardware and software. It uses similar equipment as virtual reality but users of augmented reality do not lose touch with reality, which is implemented with additional information into real-time eyesight, helping surgeons to become more efficient at surgeries (Fig. 3). Several start-ups are developing augmented reality devices that could be used in the medical field. The most basic application of aug-mented reality is the superimposition of computer-generated images on real-world images captured by a camera, and the display of the combination of these on a computer, a tablet, a video projector, or a portable video projection device. A more sophisticated option is a special head-mounted display which resembles eyeglasses (“smart glasses”), special pro-jectors, head tracking, and depth cameras to display images on the glasses creating an effective illusion of augmented reality. The use of a head-mounted display is advantageous because there is no obstruction in the surgeon’s view com-pared to a traditional display. A wide array of technology is available such as the Google Glass XE 22.1, Microsoft HoloLens, or Vuzix STAR 1200 XL [50].

The type of the superimposed images relies on the requirements of the specific procedure. It is especially

useful to visualize critical structures such as major vessels, nerves, or other vital tissues that are projected directly onto the patient. Three-dimensional (3D) reconstructions from computed tomography (CT), magnetic resonance imaging (MRI), and other imaging techniques can be used. The essential prerequisite is the quality of preoperative 3D reconstructions of medical images that depends on the quality of input data and the accuracy of the reconstruction system. Augmented reality can be used for training, prepa-ration for an operation, or performance of an operation.

In percutaneous stone treatment, augmented reality could be used for optimal placement of the access sheath and to improve safety by displaying positions of major vessels and adjacent organs. Targeting of the collecting system, even in the absence of dilation, could be achieved by direct visualization on the screened image. In open or laparoscopic surgery of complex stones, augmented reality could be useful to show the optimal incision of the paren-chyma in relation to the renal vasculature.

A basic and simple application of the principles of augmented reality was described by Rassweiler who used an iPad-based system to create a percutaneous access to renal cavities. Before the surgical procedure, all relevant anatomic structures were identified and marked in com-puted tomography preoperative images. During surgery, an iPad camera was used to obtain real-time images of the operative field and to superimpose on the monitor the anatomical elements previously registered. Similar aug-mented reality systems that have been applied for assisting

Fig. 3 Augmented reality. The basic principles of the use of augmented reality in surgery: a computer-generated image is superimposed on a real-world imagery captured by a camera and displayed on video or tablet or goggles

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laparoscopic nephrectomy could also be applied to percu-taneous access to renal cavities [51, 52] (Fig. 4).

Hands‑free control

Another interesting option is to utilize voice recognition to create voice commands, or to use gesture and eye movement recognition, allowing interaction with the hardware through body and eye movements thus enabling hands-free control of any assisting device [53].

3D printing

Existing technologies such as 3D printing or various simu-lation techniques could be used for modelling and planning successfully complex surgical procedures. “Pelvi-calyceal bio-modeling” [54] and “rapid prototyping” [55] have been described to create a model of individual patients’ stone-containing renal collecting systems, on which percutane-ous access can be planned and practiced prior to the actual surgery.

Live intraoperative diagnostics

Different systems have been developed to identify real-time characteristics of the tissues involved during a surgical pro-cedure. Confocal laser endomicroscopy (CLE) has been used for in vivo intraoperative “optical” biopsy of urothe-lial carcinoma of the bladder with standard ureteroscopes [56]. A surgical “intelligent” knife (iKnife) was equipped with a mass spectrometer to analyse the vaporized smoke to detect in real-time the released chemicals to identify whether

the tissue is malignant [57]. Today, the availability of high definition cameras makes intraoperative prediction of the chemical composition of a stones possible. This process is currently highly dependent to the surgeon’s experience but could be improved with the use of image analysers.

E‑health for clinicians

Artificial intelligence is a field of science concerned with the computational understanding of what is commonly called “intelligent” behaviour or “the ability to achieve human-level performance in cognitive tasks” [58]. In medicine, artificial intelligence is used for analysing complex medi-cal data [59]. There are many different techniques (artificial neural networks—ANNs, fuzzy expert systems, evolution-ary computation and hybrid intelligent systems) which are capable of solving a variety of clinical problems to help the clinician with diagnosis, therapeutic decisions and the prediction of clinical outcomes. Computer-aided diagnosis support systems (DSSs) are already available commercially (DXplain, GIDEON and Isabel), although their routine clini-cal use remains limited.

The use of computer-assisted history-taking systems (CAHTS) could help the less experienced clinicians to ques-tion patients on diseases or the intake of drugs predisposing to urinary stone formation [60].

Specific computer-aided diagnosis support systems (DSSs) could be useful for the recognition of predispos-ing diseases to stone formation, or for the evaluation of the results of the 24-h urine testing in kidney stone formers [61].

For complex cases and rare diseases, networks have been developed for remote consultation of experts that

Fig. 4 Navigated renal access. Navigated renal access using electromagnetic tracking: the needle is navigated towards a small sensor inserted via a ureteral catheter

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allow clinicians to have advice on diagnostic and treatment modalities. These platforms can also be used by surgeons for technical assistance in the operating room (telementor-ing). Furthermore, the use of robotic surgery systems still make it possible to perform surgical procedures remotely (telesurgery) [62, 63].

E‑health for patients

Mobile devices (smartphones, tablets) have become ubiq-uitous and subsequently there has been a growth in mobile applications. A growing number of mobile applications are being developed for personal lifestyle and medical health care support. Mobile devices can support self-management and lifestyle changes for chronic diseases. A lot of appli-cations have been developed and marketed to help losing weight or to check patients with chronic diseases such as type 2 diabetes [64].

Specific applications for renal stone formers can be devel-oped to measure the dietary intake of nutrients associated with the risk of stone formation and the acid load of the diet.

The use of wearable sensors to monitor hydration could be useful to increase compliance to water intake [65]. Pro-totypes based on different technologies (silver nanowires, microwaves, infrared light, sweat analysis) were developed and devices are expected to be marketed in the near future. Sensors (bands or patch to attach to the skin) can be con-nected to a smartphone or a smart watch. They will be able to monitor hydration levels and send alerts how much flu-ids should be drunk and when. Other information could be checked in real time such as heart rate, blood pressure, calo-ries burned, level of activity, sleep patterns, stress levels, and others. Data collected could be saved and stored for analysis by synchronizing smartwatches with specific mobile appli-cations or existing health applications (Google Fit, Apple Health, Withings App and InKin).

Finally, patient follow-up can be improved through the use of apps [66] and portals to which the patient can connect remotely without having to go to the doctor’s office [67].

Education and training (HA)

Training of urology residents to become competent stone surgeons is a demanding task. The various aspects of train-ing currently include teaching technical skills, team play, communication skills, clinical decision-making and, most importantly, post-treatment comprehensive collaborative stone management. There are various types of training models. These include the classical master–apprentice type urological and fellowship training, and then the more con-temporary simulation-based training model.

To perform optimally in the operating room (OR) as a stone surgeon, one has to work with gadgets. Developing technical skills means not only to master the technique of surgery, but also to be able to handle and understand abilities and limitations of endourological instruments. There is a wide variety of endourological instruments, disposables and other resources like imaging (fluoroscopy and sonography) that can assists in achieving desirable outcomes.

Classical surgical training based on the Halstedian prin-ciples is no longer acceptable due to various reasons. My vision is that simulation-based training and advanced fellow-ship training in endourology is the approach of the future. The “see one, do one teach one” philosophy (even when “one” does not necessarily imply a mathematical unit) is not only outmoded but in the current medical care systems with checks and balances becoming more and more impractical.

Patient safety demands that independent privileges are linked to a proven objective evidence of an individual’s ability to perform an effective and safe surgical procedure. The medical profession has learnt a great deal in simulation-based training from the aviation industry. The development of competency-based curricula in which specific benchmarks have to be achieved before moving an operator to the next level of training is an essential step in credentialing (Fig. 5). This has to be accompanied by proficiency-based curricula with well-structured end points and objective tools of train-ing [68]. An alternative way is to first establish purpose and learning outcome, following which learning objectives are set, by working backwards from the desired end points [69].

The world of simulation has wide ranging models. These include both, high and low fidelity trainers. The high fidelity trainers could be biological (animals and cadavers), non-biological, or virtual reality simulators (Fig. 6). The low

Fig. 5 Virtual reality. A student receives hands-on training on a vir-tual reality trainer for TUR-bladder tumour. Besides the teacher, a second urologist stops the time and both evaluate the performance as part of a training curriculum

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fidelity simulators have the advantage of reusability, lower cost and portability.

More recently, the use of media technology has been used to enhance learning. It has its obvious advantages including preferred time and place for use, and built in feedback sys-tems helping the user to progress to the next level.

From the trainers’ perspective, percutaneous nephroli-thotomy (PCNL) is one of the most challenging endouro-logical procedures. Teaching safe access is the corner stone of attaining proficiency in performing percutaneous renal surgery. Vascular and visceral injury is the main concern. Ather et al. [70] described the difficulties in training junior residents in the art of percutaneous access and the possible solutions. de la Rosette [71] studied the learning curve for residents and noted that they have to perform ~ 24 PCNL procedures to obtain a good proficiency during the residence period. Competence at performing PCNL is reached after 60 cases, and excellence is obtained at > 100 cases.

There are numerous low fidelity simulators that are described in the literature for training endourology and lap-aroscopy. Tawfik and colleagues reported a sponge trainer for teaching percutaneous access in PCNL. They noted that the sponge trainer was found to be a reproducible and low-cost simulator to help junior urologists to perform calyceal access, and achieved face, construct, and criterion validity. We reported a “glove model” for training laparoscopic pye-loplasty and noted that operating time and quality of sutur-ing improves with experience [72].

Recently, Inoue et al. [73] assessed Smart Simulator, a new advanced bench training model for achieving profi-ciency in flexible ureteroscopy (fURS), for content and face validity. They noted that training in situations in near-real fURS surgical fields may improve trainees’ technical skills. Similarly, Al Jabir [74] and colleague were able to validate an advanced scope trainer in a cadaveric model for face, construct, and concurrent validity.

There are many examples of e-learning portals for mini-mally invasive surgery (MIS) such as the TELMA system, EAU’s e-basic laparoscopic urological skills, e-basic robotic urological skills etc.

The significance of learning non-technical skills (NTS) is considered crucial for effective and safer conduct of sur-gical practice for an endourologist [75]. Many investiga-tors have noted that the lack of non-surgical skills corre-lates with poor technical skills and a higher mortality rate [76]. NTS has many facets including cognitive, social and personal domains. The cognitive domain deals with situa-tion awareness, decision-making and planning. The social resource factors help in developing communication skills, teamwork and leadership abilities. The personal resource centre helps in individuals’ ability to cope with stress and fatigue. The training of NTS could either be in a classroom set up, in simulation centres, or in the operating room itself. The classroom teaching is didactic teaching by interactive video analysis, whereas in the simulation centre high fidelity simulation is used for training with the behaviours (NTS) observed and recorded, and then constructively fed-back in structured debriefing sessions [77].

As the incidence of urolithiasis is increasing and the fact that it is also a highly recurrent conditions, post treatment strategies are as important as the acute management of stones. The early identification of modifiable risk factors is important to decrease the recurrence and long-term morbid-ity of recurrent urolithiasis. This morbidity not only includes development of chronic kidney disease but also other asso-ciated medical conditions. The three broad groups of risk assessment post-treatment include medical and metabolic risk factors, nutritional and anatomical abnormalities of the urinary tract. Most urologists are only trained to assess the later, and consequently, the former two are often overlooked. To comprehensively assess these risk factors, a collabora-tive approach with nutritionists and nephrologists with inter-est in metabolic evaluation of stone formers is important [78]. Nutritional advises related to increased fluids, veg-etables and fruits is well known, however, more specific advise entails detailed nutritional assessment, identifying lithogenic food in the diet of an individual, and developing strategies for prevention of recurrence of stones and devel-opment of metabolic syndrome. The impact of metabolic evaluation and strategies in developing prevention is dis-cussed in the earlier part of this paper. It is quite evident that there is no uniform advise for urolithiasis patients apart from an increased fluid intake. The type of stones formed, and specific nutritional and metabolic aberrations require a personalised treatment approach. Evaluation in a proper stone clinic therefore is essential to develop a personal-ized management strategy according to risk of recurrence, stone burden, the presence of associated comorbidities, and patient’s motivation [79]. Data from various well-conducted

Fig. 6 High fidelity trainers. Example of a high-fidelity TUR-prostate virtual reality trainer

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studies have demonstrated that strict adherence to dietary and medical advice as a preventive strategy does indeed work. However, long-term compliance is one of the major obstacles. Various strategies have been recommended and more recently Kok [66] suggested the use of a smart phone app to improve patient compliance. Another concern is the side effects of a long-term use of medication. The two most commonly used medications for urolithiasis are potassium citrate and thiazide diuretics. The risk–benefit assessment of these medications has recently been assessed in a paper by Raffin and colleagues [80]. The authors’ noted that stone formers on these medications have a better related quality of life across all domains on the Wisconsin Stone Quality of Life questionnaire. Authors also noted that these medica-tions do not increase the incidence of gastrointestinal and sexual complaints or fatigue.

In essence, training endourologists in percutaneous, retro-grade renal and ureteral surgery and laparoscopy is a tedious and time-consuming task. Current standards in patient safety dictate that residents be fairly competent in basic instrument handling skills, basic surgical skills, know-how of dispos-ables, and judicious and safe use of radiation and irrigation, before being inducted to supervised surgery. In the future, similar to airline pilots, trainees in surgery and, more impor-tantly, endosurgery will have to mandatorily fulfil a training curriculum on simulators and/ or bench trainers before being credentialed for hands-on exposure on real patients. Train-ing resident in urology in developing competence in assess-ing risk factors for recurrent urolithiasis and recommending strategies for prevention is also important to decrease the overall burden of stone disease and its impact on health care systems.

Synopsis (NB)

Given the above, there is no doubt that the field of urolithi-asis is very much alive, evolving and progressing. Sophisti-cated technologies drive the field forward, be it in research, surgery or training.

Many stone researchers have seen and regretted that there has not been a real breakthrough for decades now. To find meaningful mechanisms of clinically applicable stone prevention, the limited funds available should be used to research priority areas, foremost crystal–cell interaction. Certain areas of stone research have been exhausted and the body of literature available should suffice as background knowledge in those. As stone research is not attracting much funding, let us hope that Prof. Rodgers’s appeal does not go unheard.

Surgical stone treatment is likewise very much tech-nology-driven. This applies to the evolution of existing technologies and instruments. In addition, robotics, IT and communication software, and artificial intelligence are all

new kids on the bloc, but promising and certainly slowly but surely making their way into medicine in general, and endourology in particular.

Finally, technology, systems and instruments are only as good as the people that create, steer and use them. Sur-geons will be needed for some time to come. The idea to be medically or surgically treated by a fully automated, artificially thinking and robotically performing system will most certainly be not very appealing to most of us. On the other hand, patients do not want to be trained on, and want to be utmost safe. Surgical training therefore has to take on a new dimension, away from the patient towards virtual reality until the skill set is acceptably developed. And last but not least, we need to train our surgeons in a more holistic way to be aware and able to implicate risk assessments and prevention strategies for stone disease as an integrated part of their curriculum.

Funding This study received no funding from any source.

Compliance with ethical standards

Conflict of interest All authors declare no conflict of interest.

Ethical approval This article does not contain any studies with human participants or animalsperformed by any of the authors

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