Azal Neto W. et al., 2020: Prediction of stone-free rates following extracorporeal shockwave lithotripsy in a contemporary cohort of patients with stone densities exceeding 1000 HU
Azal Neto W, Reis LO, Pedro RN.
Department of Urology, State University of Campinas, Unicamp, Campinas, Brazil.
Department of UroScience, Pontifical Catholic University of Campinas, PUC-Campinas, Campinas, Brazil.
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.
Scand J Urol. 2020 Aug;54(4):344-348. doi: 10.1080/21681805.2020.1782981. Epub 2020 Jun 29. PMID: 32597283
Successful SWL depends on careful selection of patients. For his reason guidelines usually recommend exclusion of patients with large and hard stones. Accordingly, stones with a density exceeding 1000 HU are considered unsuitable for SWL. Similarly, stones with a diameter >20 mm as well as stones located in the lower calyx are considered less appropriate for SWL.
It therefore is interesting to learn from this report that stones with a density exceeding 1000 HU (average density 1210 HU ; range 1000-1558) were completely disintegrated in 86.5% of the patients if the diameter was