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How do we assess the efficacy of Ho:YAG low-power laser lithotripsy for the treatment of upper tract urinary stones? Introducing the Joules/mm3 and laser activity concepts

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Abstract

Objectives

To estimate the total energy needed to ablate 1mm3 of stone volume (Joules/mm3) during flexible ureteroscopic lithotripsy using a low-power Ho:YAG laser device, as a proxy of lithotripsy efficacy.

Patients and methods

We selected 30 patients submitted to flexible ureteroscopy for renal stones whose volume was bigger than 500 mm3. A 35 W Ho:YAG laser (Dornier Medilas H Solvo 35, Germany) was used for every procedure with a 272 µm laser fiber. We recorded laser parameters, the total energy delivered by the laser fiber, the time from the first laser pulse until the last one (lithotripsy time), and the active laser time as provided by the machine. We then estimated J/mm3 values and determinants, along with ablation speed (mm3/s), and laser activity (ratio between laser active time and lithotripsy time).

Results

Median (IQR) stone volume and stone density were respectively 1599 (630–3502) mm3 and 1040 (753–1275) Hounsfield units (HU). In terms of laser parameters, median (IQR) energy and frequency were 0.6 (0.4–0.8) J and 15 (15–18) Hz. Median (IQR) total delivered energy and lithotripsy time were 37,050 (13,375–57,680) J and 68 (36–88) min, respectively. Median (IQR) J/mm3 and ablation speed were, respectively, 19 (14–24) J/mm3 and 0.7 (0.4–0.9) mm3/s. The laser was active during 84% (70–95%) of the total lithotripsy time. HU density > 1000 was associated with reduced efficacy.

Conclusions

It is possible to perform laser lithotripsy using a low-power laser device with a virtually continuous laser activity. The estimation of the pre-operative parameters as well as the J/mm3 values are fundamental for a proper pre-operatory planning.

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Acknowledgements

Prof. Olivier Traxer is a consultant for Coloplast, Rocamed, Olympus, EMS, Boston Scientific and IPG

Funding

None.

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Authors and Affiliations

  1. Sorbonne Université, GRC no 20, Groupe de Recherche Clinique Sur La Lithiase Urinaire, Hôpital Tenon, 75020, Paris, France

    Eugenio Ventimiglia & Frédéric Panthier

  2. Sorbonne Université, Service d’Urologie, AP-HP, Assistance-Publique Hôpitaux de Paris, Hôpital Tenon, 4 rue de la Chine, 75020, Paris, France

    Eugenio Ventimiglia, Frédéric Panthier, Steeve Doizi & Olivier Traxer

  3. Division of Experimental Oncology/Unit of Urology, URI; IRCCS Ospedale San Raffaele, Milan, Italy

    Eugenio Ventimiglia, Steeve Doizi & Olivier Traxer

  4. Department of Urology, Hospital Carlos Van Buren, Valparaiso, Chile

    Felipe Pauchard

  5. Department of Urology, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil

    Antonio Rebello Horta Gorgen

  6. PIMM, UMR 8006 CNRS-Arts Et Métiers ParisTech, 151 bd de l’Hôpital, 75013, Paris, France

    Frédéric Panthier

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  1. Eugenio Ventimiglia
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  2. Felipe Pauchard
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Correspondence to Olivier Traxer.

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Ventimiglia, E., Pauchard, F., Gorgen, A.R.H. et al. How do we assess the efficacy of Ho:YAG low-power laser lithotripsy for the treatment of upper tract urinary stones? Introducing the Joules/mm3 and laser activity concepts. World J Urol 39, 891–896 (2021). https://doi.org/10.1007/s00345-020-03241-9

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