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
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