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TAIPEI, TAIWAN ( - Introduction and objectives: Optimal ureteral stent placement depends upon accurate estimation of ureteral length. Conventionally, CT measurements of ureteral length measure a single dimension. In this study, we compare ureteroscopically measured ureteral length to the CT + 20% method and a novel method base on the Pythagorean theorem that considers the ureteral length in all three dimensions.

wceMethods: Preoperative CT scans were reviewed for 55 patients undergoing flexible ureteroscopy. The ureteral length was estimated on the axial (a), saggital (s) and coronal (c) views. Using the Pythagorean theorem, the ureteral length (U) was determined using the derived equation: U=√(s2 + c2 - a2). Ureter length was also calculated by adding 20% to the measurement in axial length. These two methods were then compared to the direct measurement of ureteral length measured by noting the location of the UPJ and UVJ on the external surface of the ureteroscope at the meatus. The distance between the two points on the endoscope was the ureteroscopically measured ureteral length. Pearson correlation coefficient was used for statistical comparison, with p < 0.05 considered significant.

Results: The Pearson correlation coefficient of actual length with axial measurement + 20%was 0.239 (p = 0.079). There was a better correlation using the novel Pythagorean theorem method that significantly correlated with the actual length 0.325 (p = 0.016).

Conclusions: We report a novel Pythagorean based mathematical model to predict ureteral length based upon preoperative CT imaging. This technique provides higher correlation to actual ureteral length compared to conventional methods. Use of this model may improve outcomes of stent placement.

Source of Funding: None

View an interview with Nazih Khater, one of the authors of this study.


Presented by Nazih Khater, Roger Li, Muhannad Alsyouf, Michelle Lightfoot, Carol Conceicao, Christopher Chung, Gaudencio Olgin, Javier Arenas, Evan Lehrman, Jason Smith, and D. Duane Baldwin at the 32nd World Congress of Endourology & SWL - September 3 - 7, 2014 - Taipei, Taiwan

Loma Linda University Medical Center, USA


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