Purpose. Our purpose was to determine the best sonographic and color Duplex predictors differentiating
tubal ring of ectopic pregnancy and the corpus luteum cyst of pregnancy. Methods. Prospective study of 73
pregnant women with empty uterus and questionable adnexal cystic structure devoid of fetal pole or yolk sac
were included in this study. All cases underwent comprehensive transvaginal ultrasonography. Each adnexal
structure was evaluated for six specific sonographic and color Duplex characteristics: the echogenicity
of the wall in comparison to the endometrium and ovary, the wall thickness and internal echotexture,
percentage of wall circumference by flow and resistive index of the flow. Results. Thirty four of the 73
questionable adnexal structures were ectopic pregnancy, and 39 were corpora lutea. Hyperechoic wall than
the endometrium had 100% specificity and positive predictive value for diagnosing ectopic pregnancy. Iso
or hypoechoic wall than the ovary had 91.2% specificity and 90% positive predictive value for diagnosing
corpus luteum. Solid or turbid contents are predictive for ectopic pregnancy in contrast to clear contents
which was predictive for corpus luteum. RI of less than 0.4 had a specificity of 100% for diagnosing EP,
and RI of more than 0.7 had a specificity of 96.4% for diagnosis of EP. There was no significant difference
in extent of the flow between the two groups. Conclusion. Echogenic cyst wall than the endometrium, thick
cyst wall with turbid or solid contents, as well as resistive index less than 0.4 or more than 0.7 are useful
sonographic predictors for differentiating ectopic pregnancy from corpus luteum cyst.