Real-time ureteral identification with novel, versatile, and inexpensive catheter

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.