Predicting the therapeutic effect of extracorporeal shockwave lithotripsy by non-enhanced computed tomography in renal stones

초록

Purpose: To evaluate the value of non-enhanced computed tomography (NECT) as a predictor of renal stone destruction by the use of extra-corporeal shock wave lithotripsy (SWL). Materials and Methods: The study included 34 patients with a renal stone diagnosed by NECT. The stone location and size, body mass index (BMI), Hounsfield units (HU) density, and skin-to-stone distance (SSD) were assessed. The SSD was calculated by averaging three distances from the skin to the stone (at 0°, 45° and 90° angles) on NECT. The HU density was evaluated by measuring three different areas of the stone on NECT. Failure of disintegration was defined as no fragmentation or expulsion of the stone after three sessions of SWL. Results: Failure of disintegration was observed in 14 patients (41.2%). The mean SSD was 8.70±0.75cm for patients where SWL failed to disintegrate the stone (failure group) versus 6.90±1.19cm for patients where SWL successfully disintegrated the stone (success group) (p<0.01). The mean BMI of the failure group (26.37±2.29kg/m2) was significantly higher than that of the success group (23.36±3.48k g/m2) (p<0.01). Stone laterality, size, and HU density were not related to the stone fragmentation rate (p>0.05). By multivariate analysis, SSD was found to independently decrease the stone fragmentation rate of a renal stone (p=0.013; odds ratio=6.219). Conclusions: The SSD on NECT and BMI may predict the success of SWL for a renal stone.

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