objective: Ureters are at risk of injury in settings of inflammation and distorted anatomy. The use of a fluorescent dye can improve intraoperative ureteral identification without the need for any additional invasive procedures. Our team has previously described the development of a preclinical ureter-specific dye, UL-766, tested in a rat model. Here, we present the use of the fluorescent dye during laparoscopy to assist in ureteral identification in a swine model with an inflamed abdomen; the results of this study serve as proof of feasibility for use in the setting of tissue edema and erythema. methods: With institutional approval, two 20-25?kg pigs underwent abdominal surgery with the use of a Food and Drug Administration-approved fluorescence laparoscopic system. Using standard laparoscopy, inflammation was induced with sharp and blunt dissection and irritation was induced with gauze. The animals were allowed to recover and returned to the operating room after 7 days. Images of the inflamed right retroperitoneum, with fluorescence imaging, turned on, were taken before and after intravenous injection of the novel fluorescent dye at 120?μg/kg. The time until fluorescence visualization of the ureters was measured, and the fluorescent signal was measured for up to 4?hours from the time of the initial dye injection. Partial and complete transection of ureteral injuries was made by scissors and monitored under both standard video and fluorescence laparoscopy. results: Inflammation reduced the certainty of ureter identification by white light alone. Despite surrounding tissue erythema and edema, ureteral visualization under fluorescence laparoscopy was achieved within 5-10?minutes after dye injection. The fluorescent signal remained visible for at least 4?hours after injection, and the fluorescent dye showed a partial ureteral injury that would not have been observed under standard laparoscopy. conclusions: UL-766 is a preclinical fluorescent dye useful for the intraoperative identification of the ureters and ureteral injuries in an inflamed abdomen. With the acquisition of additional preclinical data, this novel dye can be a valuable tool during laparoscopic abdominal and pelvic surgeries. Lasers Surg. Med. ? 2019 Wiley Periodicals, Inc.