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Gap between UAS and ureteroscope predicts renal stone-free rate after flexible ureteroscopy with the fragmentation technique

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Abstract

Purpose

To assess the effect of our new classification on surgical outcomes after flexible ureteroscopy (fURS) for kidney stones.

Methods

We retrospectively examined 128 patients after single renal fURS procedures performed using ureteral access sheaths (UASs) with the fragmentation technique. Based on the gap (calculated by subtracting the ureteroscope diameter from the UAS diameter), enrolled patients were divided into three groups: small (< 0.6 mm), medium (0.6 to < 1.2 mm), and large space groups (≥ 1.2 mm). Stone-free (SF) status was defined as either complete absence of stones (SF) or the presence of stones < 4 mm in diameter on non-contrast computed tomography (NCCT).

Results

The SF rate was significantly lower in the small space group (50% in small, 97.9% in medium, 89.2% in large; p = 0.001). Perioperative complications over Clavien–Dindo Grade I were observed in 16.7%, 4.2%, and 8.1% of patients, respectively (p = 0.452). The ratio of stone volume and operative time (efficiency of stone removal) was significantly higher in the large space group compared to the small and medium space groups (0.009 ± 0.003 ml/min, 0.013 ± 0.005 ml/min, 0.027 ± 0.012 ml/min, respectively; p < 0.001).

Conclusion

Our findings that gaps > 0.6 mm (1.8 Fr), including the combination of a 9.5-Fr UAS and a small caliber ureteroscope, improve SF rates, and larger gaps facilitate stone removal efficiency providing the basis for future development of clinical protocols aimed at improving outcomes.

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Funding

This study was funded by a Grant-in-Aid for Scientific Research (C) 19K09718 (to M.J. and K.M.)

Author information

Authors and Affiliations

  1. Department of Urology, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama, Kanagawa, 236-0004, Japan

    Mitsuru Komeya, Takehiko Ogawa & Masahiro Yao

  2. Department of Urology, Yokohama City University Medical Center, 4-57 Urafune, Minami-ku, Yokohama, Kanagawa, 223-0024, Japan

    Mitsuru Komeya

  3. Department of Urology, Ohguchi East General Hospital, 2-19-1 Irie, Kanagawa-ku, Yokohama, Kanagawa, 221-0014, Japan

    Hisakazu Odaka, Takahiko Watanabe, Hirokazu Kiuchi & Junichi Matsuzaki

Authors
  1. Mitsuru Komeya
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  2. Hisakazu Odaka
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  3. Takahiko Watanabe
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  4. Hirokazu Kiuchi
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  5. Takehiko Ogawa
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  6. Masahiro Yao
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  7. Junichi Matsuzaki
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Contributions

MK: project development, data collection, and manuscript writing. KO: data collection. TW: data collection. HK: data collection. TO: project development and manuscript editing. MY: project development. JM: project development.

Corresponding author

Correspondence to Mitsuru Komeya.

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There are no conflicts of interest to report.

Ethics approval

This study was approved by the Institutional Ethics Committee of Ohguchi East General Hospital.

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All study participants, or their legal guardian, provided informed written consent prior to study enrollment.

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No additional data are available.

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Komeya, M., Odaka, H., Watanabe, T. et al. Gap between UAS and ureteroscope predicts renal stone-free rate after flexible ureteroscopy with the fragmentation technique. World J Urol 39, 2733–2739 (2021). https://doi.org/10.1007/s00345-020-03459-7

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  • DOI: https://doi.org/10.1007/s00345-020-03459-7

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