Randomized comparative study of indocyanine green and India ink for colonic tattooing: an animal survival study.

Indocyanine green has been reported previously as a useful agent for colonic tattooing, but its durability, ease of use, cost, and safety have not been compared with India ink. Eight pigs were randomized to colonic tattooing using sterile indocyanine green or India ink injected through tandem filters. The animals were recovered and killed after 2 weeks and were examined. All animals survived the study period with no complications. We identified 17 of 29 (59%) indocyanine green tattoos and 48 of 52 (92%) India ink tattoos at autopsy (p = 0.0003). Histologic reactions were mild and were distributed similarly in each group and the intensity of the tattoos diminished similarly in both groups. Although indocyanine green was slightly more expensive, it was easier to handle compared with India ink. Both indocyanine green and India ink tattoos cause only mild histologic reaction in the swine colon when examined 2 weeks after injection. India ink is superior to indocyanine green, when used for colonic tattooing.