Endoscopic tattooing of the colon. An experimental study.

Methods of "tattooing" the colon endoscopically were evaluated in a series of studies on dogs. Injections were performed through a sigmoidoscope using a 25-gauge sclerotherapy needle. The first phase showed excellent staining with methylene blue; however, after 24 hours the stain had completely diffused and was no longer visible. In the second phase, eight agents were evaluated for durability at the site of injection. Only indocyanine green and india ink remained visible on the serosal surface of the bowel after 48 hours. While indocyanine green showed no adverse tissue reaction, india ink caused a significant inflammatory infiltrate with microhemorrhage and thrombosis. The final phase confirmed the staining qualities of indocyanine green. The dye persisted for seven days, and no adverse reactions were noted, either macro- or microscopically. Based on our findings, indocyanine green is an excellent agent for use in tattooing the colon to facilitate intraoperative localization of small colonic lesions. Clinical trials to evaluate the efficacy and safety of this agent in humans are warranted.