Localization of hematoporphyrin derivative in injured bladder mucosa. An experimental study

Hematoporphyrin derivative, a fluorescent mixture of porphyrins, has the putative property of being retained in neoplastic tissue after systemic administration. This preferential retention is the basis for the use of this agent as a tumor localizer and tumor photosensitizer. The retention of hematoporphyrin derivative in non-neoplastic but regenerating urothelium has not been reported. In this study, thermal urothelial injury was induced in Fischer 344 rats. Animals were then injected intravenously with hematoporphyrin derivative at 3 days, 1, 2, 3 and 6 weeks after injury. Photography under ultraviolet illumination was used to detect porphyrin fluorescence in the bladder mucosa. Up to 3 weeks after injury porphyrin fluorescence was detectable in areas of inflammation and hyperplasia around the area of injury. This study suggests that in this experimental model HpD fluorescence is not specific for neoplasia.