Prior to the identification of a yolk sac or embryo in the gestational sac, the intradecidual sign may be helpful to confirm an IUP. The intradecidual sign consists of an intrauterine fluid collection with a hyperechoic rim located in the endometrium separate from the central echogenic line that represents the collapsed endometrial cavity [4,5]. This sign, which can be visualized as early as 4.5 weeks, increases the probability of an IUP but is not reliable for diagnosing an IUP [6,7]. It can be difficult to apply the intradecidual sign in some patients, as the central echogenic line is not always evident. The double decidual sac sign, typically defined as two echogenic rings around the intrauterine fluid collection, is another finding that seems to increase the likelihood of an IUP but is not a reliable sign and is of limited usefulness for confirming an IUP [7-9]. The intradecidual sign and the double decidual sac sign both have poor interobserver agreement and neither is required for the diagnosis of an IUP [7]. Before a yolk sac or embryo is seen, there has been concern that fluid in the endometrial cavity, sometimes termed a pseudogestational sac, might be confused for a gestational sac. However, pseudogestational sacs can usually be recognized based on their shape (acute angle at the edge), contents (internal echoes), or location (in the endometrial cavity) [10]. If a nonspecific fluid collection in the uterus does not have the features of a pseudogestational sac, it should be interpreted as likely representing a gestational sac, and one should generally Reprint requests to: publications@acr.org First Trimester Vaginal Bleeding not undertake a treatment that could cause unintended harm to an IUP [7,10]. Rarely, a decidual cyst [11] could be mistaken for a gestational sac but usually does not have an echogenic rim and is usually not adjacent to the central echogenic line of the collapsed endometrial cavity.
First Trimester Vaginal Bleeding. Prior to the identification of a yolk sac or embryo in the gestational sac, the intradecidual sign may be helpful to confirm an IUP. The intradecidual sign consists of an intrauterine fluid collection with a hyperechoic rim located in the endometrium separate from the central echogenic line that represents the collapsed endometrial cavity [4,5]. This sign, which can be visualized as early as 4.5 weeks, increases the probability of an IUP but is not reliable for diagnosing an IUP [6,7]. It can be difficult to apply the intradecidual sign in some patients, as the central echogenic line is not always evident. The double decidual sac sign, typically defined as two echogenic rings around the intrauterine fluid collection, is another finding that seems to increase the likelihood of an IUP but is not a reliable sign and is of limited usefulness for confirming an IUP [7-9]. The intradecidual sign and the double decidual sac sign both have poor interobserver agreement and neither is required for the diagnosis of an IUP [7]. Before a yolk sac or embryo is seen, there has been concern that fluid in the endometrial cavity, sometimes termed a pseudogestational sac, might be confused for a gestational sac. However, pseudogestational sacs can usually be recognized based on their shape (acute angle at the edge), contents (internal echoes), or location (in the endometrial cavity) [10]. If a nonspecific fluid collection in the uterus does not have the features of a pseudogestational sac, it should be interpreted as likely representing a gestational sac, and one should generally Reprint requests to: publications@acr.org First Trimester Vaginal Bleeding not undertake a treatment that could cause unintended harm to an IUP [7,10]. Rarely, a decidual cyst [11] could be mistaken for a gestational sac but usually does not have an echogenic rim and is usually not adjacent to the central echogenic line of the collapsed endometrial cavity.