Improved urethral fluorescence during low rectal surgery: a new dye and a new method

Accidental injury to the urethra remains a significant risk during complex pelvic operations. Surgeons currently lack reliable methods to visualize this structure in real-time. This gap motivated the development of fluorescence-guided techniques. Prior research has shown that near-infrared imaging can enhance tissue contrast. However, existing dyes often suffer from poor penetration or leakage. That uncertainty drove the investigation into novel contrast agents. No prior work had resolved the challenge of maintaining visibility without contaminating surrounding surgical fields. This study addresses these limitations by testing two distinct visualization approaches.

The aim of this study was to demonstrate the highlighting of the urethra during surgery using two distinct methods. Researchers sought to address the difficulty of identifying the urethra during low rectal procedures. This challenge often leads to accidental damage to the urinary tract. The team investigated whether a new near-infrared fluorophore could improve anatomical visibility. They also explored the utility of an indocyanine green and silicone mixture applied to catheters. The motivation was to provide surgeons with more reliable real-time guidance. No prior study had compared these specific approaches for urethral identification in a cadaveric model. This research provides a foundation for enhancing safety during complex pelvic operations.

The researchers conducted this investigation using male cadavers provided by the University of Oxford anatomy department. A custom-built laparoscopic system enabled the detection of near-infrared signals during the experimental trials. To evaluate the first agent, the team performed a perineal incision to infiltrate the urethra directly. This procedure involved combining the fluorophore with a specialized gel medium. For the second approach, the investigators prepared a Foley catheter coated with a mixture of indocyanine green and silicone. This catheter was set before insertion to simulate a transanal total mesorectal dissection. The study design focused on comparing the visibility and handling characteristics of both contrast techniques. Each method underwent rigorous testing to determine its suitability for identifying the urethra during simulated surgical conditions.

The investigation revealed that IRDye800BK provides excellent visualization of the urethra at a tissue depth of 2 cm. This fluorophore demonstrated superior penetration capabilities during the fluorescence excitation tests. The ICG-silicone catheter also produced high-quality fluorescence signals throughout the simulated procedures. A key advantage of the catheter method was the absence of residual dye after its removal. No leakage occurred, which kept the surrounding surgical field clean during the simulated dissection. These results indicate that both techniques effectively highlight the target structure under near-infrared light. The findings confirm that the new dye and the catheter coating are both functional for anatomical identification. The data suggest that these tools offer distinct benefits for improving surgical precision in the pelvic region.

The authors propose that IRDye800BK serves as a viable alternative to traditional agents for urethral imaging. This dye exhibits superior tissue penetration compared to standard options. The researchers suggest that deeper visualization could facilitate earlier identification of anatomical structures. Such early detection might help surgeons avoid incorrect surgical planes during rectal procedures. The ICG-silicone catheter provides a clean method for highlighting the urethra without leaving residual fluid. This approach minimizes contamination risks during the operative process. The team concludes that these methods expand the potential for advanced fluorescence-guided surgery. Future applications may benefit from the integration of these technologies into standard clinical workflows.