Reinforcement of the Triple D score with simple addition of the intrarenal location for the prediction of the stone-free rate after shockwave lithotripsy for renal stones 10–20 mm in diameter

  • Osamu IchiyanagiEmail author
  • Hiroki Fukuhara
  • Masayuki Kurokawa
  • Takuji Izumi
  • Hitoshi Suzuki
  • Sei Naito
  • Hayato Nishida
  • Tomoyuki Kato
  • Norihiko Tsuchiya
Urology - Original paper



We investigated the clinical efficacy of the Triple D score (TrD-S) on stone-free rate (SFR) prediction following shockwave lithotripsy (SWL) for renal stones 10–20 mm in diameter and modified the scoring system to improve outcome prediction.


We retrospectively examined clinical data from the medical records of 226 consecutive patients who underwent SWL for 10–20 mm kidney stones. The TrD-S was calculated according to the cutoffs of < 150 mm3 for stone volume, < 600 Hounsfield unit for stone density, and < 12 cm for skin-to-stone distance on computed tomography. The Quadruple D score was defined as the sum of the TrD-S and stone location (0/1 point for intrarenal stone distribution at lower/non-lower poles, respectively). Complete clearance 3 months after the final SWL was considered the stone-free status.


The residual group (n = 102) had significantly older age, larger stones, higher stone density, higher lower-pole stone incidence, and lower TrD-S than the stone-free group (n = 124). In the multivariate analysis, age, TrD-S, and non-lower-pole stones independently predicted the SFR. The TrD-Ss of 0, 1, 2, and 3 points showed SFRs of 40.0%, 51.9%, 73.0%, and 100.0%, respectively. The Quadruple D scores of 0, 1, 2, 3, and 4 points showed SFRs of 0.0%, 37.9%, 54.5%, 84.4%, and 100.0%, respectively, with better prediction accuracy than the TrD-S (p = 0.01).


The TrD-S is successfully validated for use in Japanese patients with 10–20-mm renal stones. Simple addition of the stone location to the TrD-S could reinforce SFR prediction after SWL.


Renal stone Shockwave lithotripsy Triple D score Lower pole 



We would like to thank Editage ( for the English language editing.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committees and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. For this type of study formal consent is not required, because the present study was retrospective and the anonymity of the participants was ensured.

Informed consent

For this type of study formal consent is not required, because the present study was retrospective and the anonymity of the participants was ensured.


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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  • Osamu Ichiyanagi
    • 1
    • 2
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  • Hiroki Fukuhara
    • 1
    • 3
  • Masayuki Kurokawa
    • 3
  • Takuji Izumi
    • 4
  • Hitoshi Suzuki
    • 5
  • Sei Naito
    • 1
  • Hayato Nishida
    • 1
  • Tomoyuki Kato
    • 1
  • Norihiko Tsuchiya
    • 1
  1. 1.Department of UrologyYamagata University Faculty of MedicineYamagataJapan
  2. 2.Department of UrologyYamagata Prefectural Kahoku HospitalKahokuJapan
  3. 3.Department of UrologyNihonkai General HospitalSakataJapan
  4. 4.Department of UrologySouth Miyagi Medical CenterOgawaraJapan
  5. 5.Department of UrologyYamagata City Hospital SaiseikanYamagataJapan

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