MP22-05 DOES CT SCAN AFTER ULTRASOUND CHANGE SURGICAL PLANNING FOR NEPHROLITHIASIS?

Abstract

You have accessJournal of UrologyImaging/Radiology: Uroradiology II (MP22)1 Sep 2021MP22-05 DOES CT SCAN AFTER ULTRASOUND CHANGE SURGICAL PLANNING FOR NEPHROLITHIASIS? Adam Ludvigson, and Piruz Motamedinia Adam LudvigsonAdam Ludvigson More articles by this author , and Piruz MotamediniaPiruz Motamedinia More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002013.05AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Ultrasound (US) is less accurate for diagnosis of nephrolithiasis than CT scan, potentially affecting surgical plans. We examined how often obtaining a CT scan after US changed the indicated management of nephrolithiasis, to identify risk factors that determine inaccurate US scans. METHODS: Approval was obtained through our institutional IRB. From those who presented to our health system over the past 3 years with suspected nephrolithiasis, we selected patients who had undergone first a retroperitoneal US, and then a CT scan within 30 days. We recorded stone size and location for all studies. We recorded stone density and skin-to-stone distance for each CT scan. Using current AUA guidelines, we determined the indicated procedure based on findings of each imaging study: shockwave lithotripsy (SWL), ureteroscopy (URS), or percutaneous nephrolithotomy (PCNL). We used Minitab software to perform general linear models and two-tailed Student's t-tests. RESULTS: 305 patients met inclusion criteria. Of these, the CT scan changed the indicated procedure 108 times (35.4%). 26 US studies indicated SWL; CT changed 19 of these (73%). 129 US studies indicated URS; CT changed 62 of these (48%). 24 US studies suggested PCNL; CT changed 9 of these (37.5%). Using CT as the gold standard, 18 US studies were false positive for stones (sensitivity=0.72). 51 US studies were false negative for stones (specificity=0.86). Average body mass index (BMI) was significantly lower in the patients with a false positive US as compared to those with a true positive US (26.59 versus 29.13 kg/m2, t(24)=2.33, p=0.029). When comparing patients who had their indicated procedure changed by the CT scan to those who did not, there were no significant differences in age, BMI, or skin-to-stone distance. However, those who had their procedure changed had significantly lower density stones (566.1 versus 747.5 HU, t(154)=2.92, p=0.004). When patients were examined in subgroups based on what their indicated procedure was before and after the CT scan, there were also no significant differences based on age, BMI, or skin-to-stone distance. There was a significant difference based on HU, with stone density explaining 22.88% of the variation (F(11,154)=4.15, p<0.001). CONCLUSIONS: US has many advantages over CT, but cannot always be used in place of it. CT scan changed the indicated stone treatment in more than 1/3 of cases in our study, and lower-density stones were a risk factor for inaccurate US findings. US should be used with particular caution in those with a history of low-density stone types, and for SWL surgical planning. Source of Funding: None © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e392-e392 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Adam Ludvigson More articles by this author Piruz Motamedinia More articles by this author Expand All Advertisement Loading ...