Sonographic Comparison of the Tubal Ring of Ectopic Pregnancy With the Corpus Luteum

Objective. Pregnant patients without a sonographically visible intrauterine pregnancy and with a thick‐walled cystic adnexal structure present a dilemma. This study compared the utility of various sonographic features in differentiating between the tubal ring of ectopic pregnancy and the corpus luteum. Methods. Retrospective review of first‐trimester transvaginal sonograms revealed a cystic adnexal structure in 79 women. Each structure was evaluated for 6 specific sonographic characteristics: echogenicity of its wall compared with that of the ovary and endometrium, wall thickness in 2 planes, color Doppler flow distribution and percentage of wall circumference, and internal texture. Results. Forty‐one (52%) of the 79 women had ectopic pregnancies, and 38 (48%) had corpora lutea. Eleven (32%) of 35 ectopic walls were more echogenic than the endometrium, compared with none of the corpora lutea. A cyst wall less echogenic than the endometrium was more likely in corpora lutea (84% versus 31%; P < .0001). More than twice as many ectopic rinds were more echogenic than ovarian tissue compared with corpora lutea (76% versus 34%; P < .0001). The only predictive internal texture feature was a clear pattern, which was more common in the corpora lutea ( P < .01, Fisher exact test). There was no significant difference in mural flow distribution or extent between the 2 groups. Conclusions. Ancillary sonographic signs to distinguish between an ectopic pregnancy and a corpus luteum include decreased wall echogenicity compared with the endometrium and an anechoic texture, which suggests a corpus luteum.