Laser-induced fluorescence of ectopic endometrium in rabbits

Endometriosis appears under a wide array of morphologies, and early microscopic disease escapes visual inspection. To improve endoscopic diagnosis, we studied the optical properties of ectopic endometrial tissue, in particular laserinduced fluorescence. Photosensitive drugs were used to obtain a selective signal. Five groups of four rabbits underwent surgical induction of endometriosis and were treated with estrogens for 5 weeks to stimulate growth of the implants. Intramuscular injections of vehicle, tetracycline hydrochloride, 6-demethyl-6-deoxytetracycline hydrochloride, tamoxifen citrate, and clomiphene citrate were given 24 hours before exposure of the tissues to argon-ion laser (351.1 nm + 363.8 nm; power density approximately 1.5 mW/cm2). Fluorescence was documented on photographic film. In controls, peritoneum and ovaries showed a dim, white-yellow fluorescence, whereas other tissues exhibited blue tones. Animals treated with tetracycline hydrochloride or tamoxifen citrate showed yellow fluorescence of active endometrial implants and the uterotomy site. Two implants, histologically without viable glandular tissue, did not fluoresce. Treatment with 6-demethyl-6-deoxytetracycline hydrochloride yielded signals of lower intensity. Clomiphene citrate caused fluorescence of the uterotomy site only. This experiment demonstrates that, of the compounds used, tamoxifen is the best selective photoenhancer for endometriotic implants and clomiphene is best for the uterotomy site. This study establishes the potential of these drugs for photoradiation diagnosis and possible treatment of diseases involving ectopic endometrium.