#04 Newsletter August 28, 2021

Hello and welcome to the stone newsletter, where we discuss every 2 months the most recent and relevant studies in stone disease.

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Themes introduction

Welcome to this summer edition of Stone News.

In this issue we first discuss the importance of ergonomics in flexible ureteroscopy and examine how the comfort of the surgeon may affect the efficiency of the surgery and the urologist’s health.

We then review low- and high-power laser lithotripsies and evaluate whether it is really necessary to reach high power in order for our stone treatments to be effective.

Finally, we discuss what happens to residual stones after ESWL, URS, RIRS and PCNL, with astonishing results.

I hope that this edition of Stone News will improve not only the care of our patients, but also of ourselves.

img Role and importance of ergonomics in retrograde intrarenal surgery (RIRS): outcomes of a narrative review. img 2'
https://pubmed.ncbi.nlm.nih.gov/34210171/ img

This review is of paramount importance in showing how poor ergonomics in RIRS may lead to work-related musculoskeletal disorders and impact on surgeon comfort and longevity. Surgeon fatigue may impair surgical performance, resulting in lower stone-free rates (SFR) and increasing the need for second-look surgery and also for repair of endoscopes.

RIRS usually entails the adoption of static postures, the wearing of heavy protective lead gowns, and repetitive actions with foot pedals and scope holding. Although 86% of urologists are reported to have experienced musculoskeletal complaints in the past 12 months, many urologists are not trained in ergonomics nor do the guidelines provide recommendations on how to avoid suboptimal ergonomics.

Prototypes of surgical chairs for use in this context have been found to offer similar results in terms of operation duration and SFR but with improvement in musculoskeletal stiffness. This line of reasoning has led surgeons to use the MEL position (lithotomy position with anti-Trendelenburg), which allows the surgeon to sit down.

Robotic assisted RIRS has been shown to have superior ergonomics but similar SFR and complication rates. Other recommendations are placement of the monitor directly in front of the viewer or on the same side to prevent neck and eye strain. The use of lightweight scopes may also lead to more comfortable surgery.

img High- and Low-Power Laser Lithotripsy Achieves Similar Results: A Systematic Review and Meta-Analysis of Available Clinical Series. img 3'
https://pubmed.ncbi.nlm.nih.gov/33677987/ img

As laser technology has advanced, new holmium YAG laser devices have been introduced, increasing the armamentarium for stone lithotripsy. New high-power lasers up to 150 W have recently been used, with application of novel concepts such as a high-frequency dusting setting with low energy (0.5 J) and high frequency (>50 Hz).

In vitro studies have shown promising initial results for high-power lasers; nonetheless, there is no clear evidence that high-power lasers are clinically more effective than the standard (low) power (30-W) lasers. The aim of this systematic review and meta-analysis was to review the evidence.

To date there have been no randomized controlled trials on the issue, and the evidence base essentially relies on non-comparative observational studies of a mostly heterogeneous nature. The review revealed no significant differences between low- and high-power lasers with respect to complications or stone-free rate (81% for high power and 82% for low power, p=0.98). While procedures using high-power lasers had a shorter mean operative time (32.9 vs 62.7 min, p<0.01), the estimated stone volumes were twofold higher in the low-power laser group (2604.4 vs 1217.1mm3, p=0.048), which could explain the difference.

Many clinical features need to be taken into account when performing laser lithotripsy: A higher frequency can lead to a lower quality of endoscopic view (which may also be impaired by microbleedings), and popcorning in the laboratory on a solid glass surface can result in a more efficient process compared with a real distensible calyx. Another issue is the higher intrarenal temperatures seen with high-power lasers; intermittent laser activation has been recommended to avoid this problem, but this solution could also increase operative time.

Taking into account all aspects, the conclusion of this first clinical comparison between low- and high-power lasers is that high-power lasers do not show a clear clinical advantage.

img Natural History of Post-Treatment Kidney Stone Fragments: A Systematic Review and Meta-Analysis img 2'
https://pubmed.ncbi.nlm.nih.gov/33904756/ img

We know that a relatively high number of patients will have residual stone fragments of varying size after treatment. This meta-analysis evaluated the course of asymptomatic (“clinically insignificant”) residual stones after ESWL, URS, RIRS and PCNL with regard to spontaneous passage, intervention rate and disease progression. Follow-up in the reviewed studies varied from <20 months to >50 months.

The rate of spontaneous stone passage ranged from 35% to 42% during the course of complete follow-up. The intervention rate varied from 24% at <49 months of follow-up to 36% at follow-up of more than 50 months. Disease progression rate was 27% and 31% for <34 months and >50 months of follow-up, respectively.

Regarding stone fragment size, the review showed a significantly increased rate of intervention in patients with larger fragments (>4 mm) and revealed that the rate of intervention increases over time regardless of fragment size. There was no difference in spontaneous passage rate or disease progression according to fragment size. The authors found that at 50 months of follow-up, the aggregate disease progression rate reached 47% for fragments of less than 4 mm and 88% for fragments larger than 4 mm.

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