SAN FRANCISCO — A double decidual sign on ultrasound can rule out ectopic pregnancy in women seeking emergency care for first-trimester pain or bleeding, Dr. Bon S. Ku said in a poster presentation at the annual meeting of the Society for Academic Emergency Medicine.
In a retrospective study of 1,339 patients with indeterminate ultrasounds, 4% of ultrasounds showed a double decidual sign without definitive signs of intrauterine pregnancy. Only 1 (2%) of these 57 patients with the double decidual sign ultimately was diagnosed with ectopic pregnancy. The other 56 had a live intrauterine pregnancy (29 patients) or an abnormal intrauterine pregnancy (27 patients), said Dr. Ku of the University of Pennsylvania, Philadelphia.
Put another way, 18% of the 1,339 patients had a final diagnosis of ectopic pregnancy, and only 1 (0.4%) of these 245 patients with ectopic pregnancy had a double decidual sign on ultrasound.
In women with first-trimester pain or bleeding and an indeterminate ultrasound, the presence of a double decidual sign makes ectopic pregnancy “extremely unlikely,” said Dr. Ku and his associates.
A double decidual sign shows a gestational sac surrounded by two echogenic rings of endometrial tissue (decidua), the decidual capsularis (inner ring) and decidual parietalis (outer ring). It is the only ultrasound finding consistently related to serum quantitative β-human chorionic gonadotropin (β-HCG) levels, and some previous studies report that a double decidual sign is a reliable indicator of intrauterine pregnancy.
Dr. Ku's institution and many other medical centers do not consider the double decidual sign to be definitive of intrauterine pregnancy, however, because its recognition is somewhat subjective, he said. A sonogram must show a yolk sac, fetal pole, or fetal heart tones to diagnose definitive intrauterine pregnancy. Clinically stable women with “indeterminate” ultrasounds that lack these definitive signs are diagnosed as “possible early intrauterine pregnancy/cannot exclude ectopic pregnancy” and asked to return in 2 days for a repeat evaluation and β-HCG measurement. Patients who fail to return are contacted by staff.
The study correlated the presence of the double decidual sign with the final diagnosis, which was determined by sonographic evidence of intrauterine pregnancy, β-HCG measurements that declined to zero, evidence of trophoblastic tissue after spontaneous abortion, or D&C for ectopic pregnancy.
The findings are limited by the small number of ultrasounds with a double decidual sign and because the study relied on ultrasound reports rather than images, Dr. Ku noted.