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Introduction and Objectives: Ureteroscopic management of impacted ureteral stones poses multiple challenges. We examined whether ureteral thickness measured on preoperative noncontrast computed tomography (CT) is predictive of stone impaction at the time of ureteroscopy (URS). Methods: Thirty-eight patients with preoperative CT scan and undergoing URS for ureteral stones were prospectively studied. Ureteral thickness directly above, around (peri-calculus ureteral thickness [P-CUT]), and below the calculus were determined on CT scan. The cross-sectional surface area around the stone (P-CUT) was also calculated. Stones were considered impacted at surgery if contrast had difficulty passing, a guidewire could not pass, and the stone was visually impacted >5 on a Likert scale. The surgeon determining intraoperative impaction and the individual measuring the ureteral thickness on CT were blinded. Results: Fourteen of the 38 patients were found to have an impacted ureteral stone at the time of surgery. Patients with an intraoperative finding of an impacted stone had significantly higher ureteral thickness above, around (P-CUT), below the calculus, and P-CUT surface area with all four p-values <0.001. P-CUT surface area was independently predictive of impaction at the time of surgery on multivariate analysis. A mean P-CUT of 6.1 and 1.6 mm and P-CUT surface area of 92.6 and 15.4 mm2 were noted for the impacted and nonimpacted stones, respectively. Conclusion: Ureteral thicknesses above, around (P-CUT), and below the calculus are readily measurable on CT scan. P-CUT surface area can also be calculated for a stronger representation of ureteral thickness. These four parameters are predictive of ureteral stone impaction and useful for surgical planning and patient counseling. [ABSTRACT FROM AUTHOR]

Objective: To evaluate whether preoperative computed tomography (CT) findings could predict the presence of an impacted stone. Preoperative identification of an impacted ureteral stone may influence patient preparation and operative decisions. Factors predicting ureteral stone impaction have not been clearly identified.Methods: We identified all patients from June 2014 to July 2016 that underwent ureteroscopic treatment of an impacted ureteral stone. Patients that had ureteral prestenting or previous treatment for their stone were excluded. Noncontrast CT images were reviewed to calculate stone size, stone volume, degree of hydronephrosis (0-3), and Hounsfield units (HU) of the stone as well as the ureter distal and proximal to the stone. These were compared with a control group of patients that had nonimpacted stones.Results: Patients with impacted stones had a greater stone size, volume, HU of the ureter under the stone, HU under/above ratio, and degree of hydronephrosis on univariate analysis. Multivariate analysis demonstrated that HU under the stone was a significant predictor of ureteral stone impaction (odds ratio 1.17; 95% confidence interval 1.11-1.25). Distal ureteral density above 27 HU demonstrated a sensitivity of 85%, specificity of 85%, positive predictive value of 89%, and negative predictive value of 81% for ureteral stone impaction.Conclusion: Impacted stones are associated with ureteral density cut-off value of 27 HU or greater. Measuring this value on preoperative noncontrast CT may help predict which patients are more likely to have impacted stones. [ABSTRACT FROM AUTHOR]