A +20% Adjustment in the Computed Tomography Measured Ureteral Length Is an Accurate Predictor of True Ureteral Length Before Ureteral Stent Placement

Abstract

The correct length of a ureteral stent is important in minimizing postplacement discomfort and stent migration. We describe and validate a method to accurately measure the ureteral length. The ureteral length in 48 patients undergoing ureteral stent placement for urolithiasis was measured by computed tomography (CT) (total thickness of axial slices between the ureteropelvic junction and ureterovesical junction) and adjusted up by 20%. The adjusted CT measurement of ureteral length was compared with direct intraoperative measurement using scatter plot and Pearson correlation coefficient. Correlation coefficients were also calculated between intraoperative ureteral length and various body habitus measurements such as the height, weight, and waist circumference. Median patient age was 62 years. The median stone diameter was 7.5 mm (1-20). The ratio of left- to right-sided stones was 2:1. The stone location was in the proximal ureter in 45.8%, distal ureter in 37.5%, kidney in 10.4%, and midureter in 6.3%. Symptoms included adnominal/flank pain (93.8%) followed by nausea/vomiting (39.6%) and gross hematuria (16.7%). Median creatinine was 1.4 (0.8-3.6 mg/dl) and median WBC was 8.6 (2.8-17.6). The median ureteral length was 25.8 cm (19.2-29.4) on the CT scan and 25.5 cm (19.0-29.0) on the intraoperative measurement (p=0.57). The Pearson correlation coefficient between the two measurements was 0.979. In contrast, the height, weight, and waist circumference correlated poorly with intraoperative ureteral length measurements (r=0.34, 0.19, and 0.40, respectively). CT-measured ureteral length adjusted up by 20% is a reliable method to accurately measure the true ureteral length. This method is superior to traditional indirect methods that rely on body habitus measurements.