A novel method for near-infrared fluorescence imaging of the urethra during perineal and transanal surgery: demonstration in a cadaveric model.

AIM: TaTME is a promising novel sphincter-saving procedure for low rectal cancer. However, the transanal bottom-up dissection is associated with increased rates of iatrogenic urethral injuries. Near-infrared fluorescence (NIRF) imaging, given its deeper tissue penetration, has been explored in a limited number of studies for enhanced intraoperative urethral visualization. In this study, we explored the feasibility of a novel, ultrabright, biocompatible fluorescent polymer to coat urinary catheters for the purpose of intraoperative urethral visualization. METHODS: In an ex-vivo experiment, using a near-infrared laparoscope, the fluorescent signal of a coated catheter (Near-Infrared Coating of Equipment - NICE) was qualitatively and quantitatively compared to the signal of indocyanine green (ICG)/Instillagel® mixtures and ICG-filled catheters at several concentrations. Also, in 3 male human torsos, using fluorescent urinary catheters, NIRF-guided perineal dissections and a TaTME were performed. Intraoperative NIRF-based urethral visualization was performed systematically. RESULTS: During the qualitative and quantitative fluorescence signal assessment, NICE-coated catheters were clearly superior to the ICG-based solutions. In the cadaveric experiments, enhanced urethral visualization was possible even at early stages of dissection, whenthe organ was covered by several tissue layers. CONCLUSIONS: NICE-coated catheters represent a promising potential to allow for NIRF-based intraoperative urethral visualization.