Absorption and preferential vagina-to-uterus distribution after vaginal administration of (99m)Tc-pertechnetate in postmenopausal women.

OBJECTIVE To investigate in vivo and in humans the mechanisms and kinetics of vagina-to-uterus distribution. DESIGN Controlled clinical study. SETTING Volunteers in an academic research environment. PATIENT(S) Six postmenopausal women undergoing transabdominal hysterectomy were selected. INTERVENTION(S) Women received 0.2 mL of (99m)Tc-pertechnetate vaginally. In three patients the cervical canal was previously sealed by means of surgical glue. Six postmenopausal women who had received (99m)Tc-pertechnetate intravenously for a thyroid scintigraphy were considered as a control. MAIN OUTCOME MEASURE(S) Radioactivity was assessed every 30 minutes for 6 hours in the pelvis and in body regions where (99m)Tc-pertechnetate normally accumulates (thyroid, salivary glands, and stomach). RESULT(S) Uterine activity appeared after 60 minutes and peaked between 120 to 210 minutes. These same times were observed in the patients who had a sealed cervix. Thyroid uptake appeared after 180 minutes and peaked between 210 and 330 minutes. Uterine uptake did not occur in any of the intravenous patients; their thyroid uptake was rapid, appearing after 30 minutes. CONCLUSION(S) Preferential vagina-to-uterus distribution, at least in postmenopausal women, is not simply due an intracanalicular passage but is mediated by absorption of substances and probably by a countercurrent transfer mechanism.