Ectopic pregnancy is one that occurs outside of the uterus and is the leading cause of first-trimester maternal obstetric morbidity. It can be asymptomatic or present with symptoms ranging from mild vaginal bleeding and lower abdominal pain to shock secondary to massive hemorrhage. Menstrual history may reveal a missed or recent abnormal menses. Pelvic examination may be normal or may include vaginal bleeding, cervical motion tenderness, or adnexal tenderness. An abnormally low or slowly rising hCG may be seen. Risk factors include use of an IUD, prior ectopic pregnancy, and a history of pelvic inflammatory disease, tubal ligation, and other abdominal or pelvic surgeries.
The visualization of an IUP on US excludes the diagnosis of ectopic pregnancy with the exception of a rare heterotopic pregnancy (both intrauterine and ectopic). A gestational sac (GS) may be seen at about 5 weeks. This is suggestive of an IUP; however, definitive diagnosis of IUP requires identification of a yolk sac. The double decidual sac sign is evidence of a true GS and should be differentiated from the single pseudogestational sac formed from a decidual cast in ectopic pregnancy. When no GS is visualized (“empty uterus”), ectopic pregnancy cannot be distinguished from an early IUP or from recently completed spontaneous abortion. Free fluid on US is concerning but not specific.
Management and Disposition
Unstable patients require aggressive resuscitation with fluid and blood, followed by surgery. Stable patients warrant immediate gynecologic consultation. Observation of an asymptomatic patient with repeat measurement of hCG and outpatient follow-up may be considered after gynecologic consultation. Medical management with methotrexate may be used in stable patients, whereas immediate surgical intervention is indicated in unstable patients. US has diminished diagnostic accuracy at lower hCG levels, and ectopic pregnancy has been observed at hCG level less than 100 mIU/mL. Therefore, obtain gynecologic consultation if there is a clinical suspicion for ectopic pregnancy regardless of the US findings or hCG level.
Empty Uterus. Free fluid seen in the pelvis in this patient with an empty uterus is concerning if ectopic pregnancy is suspected. Ectopic pregnancy should be strongly suspected if a transvaginal ultrasound reveals an empty uterus in the setting of a serum quantitative hCG level above the institution’s discriminatory zone. (Photo contributor: Lauren Oliveira, DO.)
Intrauterine Gestational Sac. Discrete ring of an intrauterine gestational sac seen on transvaginal ultrasound. No yolk sac is visualized. A double decidual sac sign is seen, lending evidence of a true gestational sac versus a pseudogestational sac formed from a decidual cast in ectopic pregnancy. A thorough look in the adnexa is important in diagnosing ectopic pregnancy when a gestational sac is the only finding. (Photo contributor: Lauren Oliveira, DO.)