Background: Although ureteral catheters and ureteral fluorescence methods have been investigated to avoid ureteral injury, they have not been standardized for procedural complexity and safety to the living body. A near-infrared (NIR) fluorescence ureteral catheter made of fluorescent resin was jointly developed for non-invasive detection of ureters. The aims of this study were to (1) evaluate its bench-top performance and (2) assert its safety and potential usefulness in a series of animal models.
Methods: [Bench-top study]: Confirmed stimulation of NIR fluorescence catheter by NIR light was investigated with the use of a laparoscopic fluorescence imaging system. Additionally, the influence of imaging distance and shielding objects, such as 1.5-mm sliced pig loin with multiple sheets, was also evaluated. [Performance study]: The safety and potential usefulness of fluorescence catheter was evaluated in five pigs. Non-fluorescence and fluorescence ureteral catheters were alternatively placed in the animals' left and right ureters. The ImageJ software was used in all experiments to quantify fluorescence signal and the signal-to-background ratio.
Results: [Bench-top study]: The fluorescence ureteral catheter was successfully identified at all distances. Its fluorescence decreased in inverse proportion to distance and to the intervening shield thickness (p < 0.01). When shields were present, catheter position could not be recognized with non-fluorescence catheters, but with fluorescence catheters they could be recognized. [Performance study]: Fluorescence catheter's ability to fluoresce at all distances was confirmed (p < 0.01). No individual differences (p = 0.21) or left/right ureter differences (p = 0.79) were observed. The fluorescence of the fluorescence catheter decreased in inverse proportion to distance (p < 0.01).
Conclusions: The new fluorescence ureter catheter investigated shows promising performance in providing ureteral identification with high specificity during laparoscopic surgery.
Keywords: Iatrogenic ureteral injury; Laparoscopic surgery; Near-infrared fluorescence; Target-to-background ratio; Ureteral catheter; Ureteral tract.