The authors collected data on 50 patients undergoing ureteroscopy for ureteral stones who had a non-contrast CT pre-operatively. Stones were considered impacted at surgery if a guidewire could not pass, contrast had difficulty passing, and the stone visually was impacted >5 on a Likert scale.
Of the 50 patients analyzed, 17 of them had evidence of an impacted stone intraoperatively. No differences were seen in terms of age, gender, BMI, ASA status, stone location, or stone size between the impacted vs. non impacted group. Patients in the impacted group, however, had a statistically higher HU reading below the stone (p<.0001), a higher likelihood of pre-op hydronephrosis (p=.01), and a higher HU below/above ratio (p=.022). HU density underneath the stone emerged as an independent predictor of impaction in multivariate analysis.
These results suggest that pre-operative noncontrast CT scans can be used to predict whether or not a stone is impacted and may able to guide expectations during surgery. Further, this information is easily obtained and does not require a radiologist’s interpretation. The presenter hypothesizes that the higher HU density below an impacted stone is due to the inflammatory changes occurring at that region as well as the resulting edema that follows. By using preoperative CT measurements, one may be able to tailor their management for these difficult cases.
Presented By: Ryan Chandhoke, MD, Urology Resident at UC Irvine Medical Center
Authors: Stephanie Purnell, Blair Gallante, Egor Parkhomenko, MD, William Atallah, MD, MPH, Mantu Gupta
Written By: Max Towe at the 36th World Congress of Endourology (WCE) and SWL - September 20-23, 2018 Paris, France