Intraoperative Ureter Visualization Using a Novel Near-Infrared Fluorescent Dye

Ureters can be accidentally severed during pelvic surgeries, significantly prolonging the times in the operating room to allow for complete repair of damaged ureters and leading to significant morbidities associated with consequent ureter obstruction and possible kidney dysfunction. In an effort to prevent these complications, light-emitting stents and urine-excreted dyes have been introduced to illuminate the ureter during surgery. However, problems with mechanical insertion, ureter spasm, image contrast, and localized injection have limited interest in their clinical applications. We report here the synthesis and characterization of a new near-infrared (NIR) fluorescent dye (UreterGlow) that can be injected systemically but is excreted primarily through the renal system, allowing ureter imaging with an NIR fluorescence camera. Following intravenous injection of 0.1 mg/kg UreterGlow, we have monitored the flow of UreterGlow through the proximal, medial, and distal segments of the ureter. The timing of ureter visualization was calculated from the time of injection of the drug. The null hypothesis was that "Visualization of the ureter in pigs is possible 60 min after administration of UreterGlow using an NIR camera". UreterGlow displayed excitation and emission maxima of λ _ex = 800 nm and λ _em = 830 nm in phosphate buffered saline, pH 7.4, and could be imaged in the urinary tract in mice. Shortly after injection of UreterGlow into Yorkshire pigs, peristalsis of the ureter could be observed. The distal ureter could be visualized under NIR illumination after 60 min with constant fluorescence in all five pigs for >2 h. The same ureters could not be seen using visible light (X ² , p = 0.0001). Because both excitation and emission of UreterGlow occurs at >30 nm longer wavelength than most tumor-imaging fluorescent dyes, it should be possible to distinguish ureter fluorescence from tumor fluorescence with this dye.