ENDOSCOPIC TATTOO AGENTS IN THE COLON - TISSUE RESPONSES AND CLINICALIMPLICATIONS

Laparoscopic surgery frequently requires tattooing of endoscopically i dentified sites for localization during surgery. Some tattooing agents cause serious tissue injury which must be recognized in pathologic ex amination. Seven surgically resected colons were reviewed after inject ion with methylene blue or India ink at intervals of I day to 7 weeks before surgery. Early reactions to India ink included necrosis, edema, and neutrophilic infiltration in the submucosa and muscularis propria , Vessels were inflamed but without fibrinoid necrosis. Early reaction s to methylene blue included ischemic ulceration, necrosis, and eosino philic infiltration in the submucosa as well as fibrinoid necrosis of vessel walls, In the repair of methylene-blue injury, obliterative int imal fibrosis was seen in vessels. Such changes were absent in the col ons injected with India ink. The India ink remained remained visible w ith the naked eye and microscopically 7 weeks after injection. Methyle ne blue was not grossly visible 7 days after injection, and only micro scopic particles of pigment remained in widely scattered macrophages, In light of these findings, the amount of ink injected should be minim ized and the injection site should be completely resected at surgery. Methylene blue is a poor tattoo agent, but its occasional use continue s, and pathologists should recognize the resulting reaction.