Lim KH et al, 2015: Can stone density on plain radiography predict the outcome of extracorporeal shockwave lithotripsy for ureteral stones?
Lim KH, Jung JH, Kwon JH, Lee YS, Bae J, Cho MC, Lee KS, Lee HW.
Department of Urology, Dongguk University Ilsan Hospital, Goyang, Korea.
Department of Radiology, Dongguk University Ilsan Hospital, Goyang, Korea.
PURPOSE: The objective was to determine whether stone density on plain radiography (kidney-ureter-bladder, KUB) could predict the outcome of extracorporeal shockwave lithotripsy (ESWL) for ureteral stones.
MATERIALS AND METHODS: A total of 223 patients treated by ESWL for radio-opaque ureteral stones of 5 to 20 mm were included in this retrospective study. All patients underwent routine blood and urine analyses, plain radiography (KUB), and noncontrast computed tomography (NCCT) before ESWL. Demographic, stone, and radiological characteristics on KUB and NCCT were analyzed. The patients were categorized into two groups: lower-density (LD) group (radiodensity less than or equal to that of the 12th rib, n=163) and higher-density (HD) group (radiodensity greater than that of the 12th rib, n=60). Stone-free status was assessed by KUB every week after ESWL. A successful outcome was defined as stone free within 1 month after ESWL.
RESULTS: Mean stone size in the LD group was significantly smaller than that in the HD group (7.5±1.4 mm compared with 9.9±2.9 mm, p=0.002). The overall success rates in the LD and HD groups were 82.1% and 60.0%, respectively (p=0.007). The mean duration of stone-free status and average number of SWL sessions required for success in the two groups were 21.7 compared with 39.2 days and 1.8 compared with 2.3, respectively (p<0.05). On multivariate logistic analysis, stone size and time to ESWL since colic and radiodensity of the stone on KUB were independent predictors of successful ESWL.
CONCLUSIONS: Our data suggest that larger stone size, longer time to ESWL, and ureteral stones with a radiodensity greater than that of the 12th rib may be at a relatively higher risk of ESWL failure 1 month after the procedure.
Korean J Urol. 2015 Jan;56(1):56-62. doi: 10.4111/kju.2015.56.1.56. Epub 2015 Jan 6. FREE ARTICLE
It is a good intention to use KUB instead of NCCT, when the previous radiological procedure gives sufficient information for the planned ESWL treatment. In this retrospective study the KUB stone density was compared with NCCT-HU when the treatment result was interpreted.
As expected stones with a high density (HU) and large size had a less favourable outcome of ESWL. In this report success was defined as no visible stones after 4 weeks. Inasmuch as anatomical factors are of importance for the final result, it might have been more appropriate to describe if the stones were disintegrated or not.
In the retrospective way in which the result was evaluated it is difficult to know exactly what could be predicted from the primary inspection of the KUB image. Was it possible to predict stone composition and ESWL effects? If such an attempt was made: how did the final outcome correspond to the prediction? This question would indeed be highly interesting in a prospective view, because by examining the stone appearance on KUB, several conclusions (assumptions) can be made about stone-composition and fragility.
Despite repeated treatment sessions of ureteral stones the success rate was lower than I expected. Unfortunately I could not find that the treatment result was reported in the matched sample comparison.