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

Aim Transanal total mesorectal excision 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 intra‐operative urethral visualization. In this study, we explored the feasibility of a novel, ultrabright, biocompatible fluorescent polymer to coat urinary catheters for the purpose of intra‐operative 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 three male human torsos, using fluorescent urinary catheters, NIRF‐guided perineal dissections and a transanal total mesorectal excision were performed. Intra‐operative 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, when the organ was covered by several tissue layers. Conclusions NICE‐coated catheters represent a promising potential to allow for NIRF‐based intra‐operative urethral visualization.