Extrauterine findings of ectopic pregnancy of transvaginal US: importance of echogenic fluid. Transvaginal ultrasound (US) studies of 232 consecutive patients with positive serum pregnancy tests who were considered to be at risk for ectopic pregnancy were prospectively evaluated to determine the significance of various extrauterine findings, including echogenic fluid in the cul-de-sac. All patients were found to have a surgically proved ectopic gestation (group 1, 68 patients [29.3%]), reliable evidence of intrauterine pregnancy at initial transvaginal US (group 2, 83 patients [35.8%]), or no evidence of pregnancy at initial transvaginal US, but subsequent proof of an intrauterine pregnancy (group 3, 81 patients [34.9%]). Adnexal findings were demonstrated in 45 (66%) group 1 patients, including a living extrauterine embryo in 10 (15%), an extrauterine gestational sac in 21 (31%), and an adnexal mass in 14 (21%). Intraperitoneal fluid was detected in 43 (63%) group 1 patients and in 81 (31%) group 3 patients. Echogenic fluid was the only abnormal finding at US in 10 (15%) group 1 patients and added confidence to the diagnosis of ectopic pregnancy in many others. Echogenic fluid correlated with hemoperitoneum at the time of surgery. The presence of echogenic fluid indicates a high risk for ectopic pregnancy in women referred with this clinical indication. 