Background and Purpose:
Both shockwave lithotripsy (SWL) and ureteroscopy (URS) may be used in the treatment of similar stones and both need fluoroscopic imaging to achieve this. Fluoroscopy, however, is a source of ionizing radiation. The purpose of this study is to compare the effective radiation dose (ERD) between patients undergoing SWL vs URS.
Patients and Methods:
The ERD was measured among consecutive patients who were undergoing either SWL or URS between January 2010 and February 2011. For SWL, ERD was calculated using fluoroscopic exposure time, current, voltage, skin-to-source distance, and field size. For URS, it was calculated from the measured dose-area product. We measured several patient and stone factors. Univariate and multivariate analyses were performed.
A total of 190 patients were included (87 SWL and 103 URS). In the univariate analyses, no differences were found in ERD (7.32 vs 6.00 mSv, P=0.262 and 7.23 vs 6.07 mSv, P=0.198, for renal and ureteral stones, respectively). In the multivariate analyses, among renal stones, SWL was associated with a higher ERD than URS (β=2.06, P=0.026), and body mass index and stone size were also significant predictors (β=0.212, P=0.045 and β=0.452, P=0.004, respectively). Among ureteral stones, no differences were found (β=0.425, P=0.674), and only the presence of a stent was related to ERD (β=2.53, P=0.013).
Among patients with renal stones, SWL was associated with a modest increase in ERD compared with URS, but for ureteral stones, both modalities were associated with similar levels of radiation. This information may be relevant for frequent stone formers needing treatments for which cumulative exposures may become significant.
J Endourol. 2012 Jun;26(6):597-601. doi: 10.1089/end.2011.0185. Epub 2011 Oct 4
PMID:21970366 [PubMed - as supplied by publisher]
The authors state: ”Among patients being treated for renal stones, SWL was found to be associated with a higher ERD (effective radiation dose). While this difference was statistically different, clinically the difference was modest.” No ultrasound localisation system that could reduce the x-ray exposure was available in the lithotripter used in this study. The authors address the problem of comparing the radiation doses in different studies. What can be compared is the fluoroscopy time: In the present study it was 476.5 (162–1788) seconds for ESWL of renal stones and 496.3 (90–1740) seconds for ureteral stones. That does not compare at all to the 129–198 (mean 120) seconds reported in the publication 19 of this review (Elkoushy MA, Morehouse DD, Anidjar M, Elhilali MM, Andonian S. Impact of Radiological Technologists on the Outcome of Shock Wave Lithotripsy. Urology. 2011 Nov 3.) The difference could also be due to the different lithotripter used in the two studies.