Background: Upper urinary tract calculi are common with multi-modalities of treatment, with continuous invention of new modalities; one of these modalities is Extracorporeal shock wave lithotripsy [ESWL], which considered the modality of choice for renal stones less than 10mm with the advantage of being less invasive compared to other modalities.
Aim of the work: To identify the factors based on Non-Contrast Computed Tomography [NCCT] that will predict the success of shock wave lithotripsy for renal stones.
Patients and methods: A retrospective, single arm interventional study conducted by reviewing the medical files of all patients who underwent SWL for renal stones in the past 2 years. The study included 120 patients [82 males, 38 females; mean age: 52.1 y]. SWL was carried out. After three sessions, failure of disintegration was defined as no fragmentation of the stone. Univariate and multivariate analyses were used to assess the impact of patients' sex, age, and body mass index] as well as the stones' laterality, position, volume, mean attenuation value, and skin-to-stone distance on disintegration.
Result: The success rate of extracorporeal SWL at 3 mo. was 91.66% [110 of 120 patients]; 100 patients were stone free and 10 had residual fragments <4 mm. The significant predictors of residual fragments were stone density, skin-stone distance and stone diameter [p 0.018, < 0.001 and < 0.001, respectively].
Conclusion: Increased stone density, skin-stone distance and stone diameter as detected by NCCT are significant predictors of failure to fragment renal stones by SWL, alternative treatment should be devised for patients with stones having Hounsfield Unit [HU] >1000 HU and/or large skin-to-stone distance [SSD].