Prediction of stone-free rates following extracorporeal shockwave lithotripsy in a contemporary cohort of patients with stone densities exceeding 1000 HU

Abstract

Purpose: Nephrolithiasis is a common urologic problem, and its incidence is increasing. Shockwave Lithotripsy (SWL) has better results for patients with stones < 1000 HU. We attempted to identify SWL stone-free (SF) predictors for > 1000 HU stones.

Methods: From January 2013 to September 2019, patient shared decision consecutive SWL for the treatment of a single > 1000 HU renal stone diagnosed by non-contrast computed tomography (NCCT). Endpoints: Fragmentation and SF or clinically insignificant residual fragments ≤ 4 mm at 4 weeks. Age, gender, stone side, location, size and density, number and average energy (Joules) of shocks were explored on uni- and multivariate regression analysis.

Results: All sixty-one patients included were diagnosed with renal stone between 5 and 20 mm (maximum length) and underwent one SWL session only: 62.3% males, median age 48 (21–80) years, mean stone size 9.43 ± 2.9 mm (6.0–20.0), mean density 1210 ± 135 HU (1000–1558). There were 39 (63.9%) cases of SF, 16 (26.2%) of partial success and six (9.8%) of no success. Stone size was the only independent predictor of fragmentation, OR = 1.83, 95% CI = 1.32–2.55, p = 0.0003, and SF OR = 1.91, 95% CI = 1.31–2.78, p = 0.008. The best discriminatory stone size on ROC analysis was 1 cm.

Conclusion: Stone size was the only significant success predictor in our cohort, with 76% SF rate for stones < 1 cm in 4 weeks follow-up, supporting that renal stones > 1000 HU may be suitable to SWL.

Keywords:

• Kidney calculi
• non-contrast computed tomography (NCCT)
• extracorporeal shockwave lithotripsy (ESWL)
• high-density stone

Author contributions

WAN: data analysis, manuscript writing. LOR: project development, manuscript editing. RNP: project development, data collection, manuscript editing

Acknowledgment

To the involved institution(s), the patients and those that provided and cared for study patients.

Disclosure statement

No potential conflict of interest was reported by the author(s).

ORCID

Leonardo O. Reis https://orcid.org/0000-0003-2092-414X.

Additional information

Funding

Reis LO: “National Council for Scientific and Technological Development” – CNPq, Research Productivity: 304747/2018-1 .