Korean J Urol.  2008 Mar;49(3):252-256. 10.4111/kju.2008.49.3.252.

Predicting the Therapeutic Effect of Extracorporeal Shockwave Lithotripsy by Non-enhanced Computed Tomography in Renal Stones

• Kim JH
• Moon YT

• KMID: 1204628
• DOI: http://doi.org/10.4111/kju.2008.49.3.252

Abstract

PUROSE: To evaluate the value of non-enhanced computed tomography (NECT) as a predictor of renal stone destruction by the use of extracorporeal 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 0degree, 45degree and 90degree 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/m(2)) was significantly higher than that of the success group(23.36+/-3.48kg/m(2))(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.

Keyword

Tomography; Lithotripsy; Urinary calculi

Figure

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  Fig. 1. The measurement of skin-to-stone distance at 0o, 45o, and 90o on an axial scan of non-enhanced computed tomography.

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  Fig. 2. A receiver operating characteristic curve demonstrating the area under the curve of 0.911. An SSD of 8cm represented the most sensitive (87%) and specific (79%) point on the curve.

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