Emergency Department Diagnosis of an Interstitial Ectopic Pregnancy Aided by Goal-directed Bedside Ultrasound

A 23-year-old female, gravida 2, para 1, at 9 weeks gestation presented to the emergency department with a 2-day history of right lower quadrant pain and light vaginal spotting. The patient had not undergone formal ultrasound during this pregnancy. The patient denied nausea, vomiting, migration of pain, anorexia, fever, dizziness, and syncope, and vital signs were normal. Examination revealed tenderness in the right adnexal region, but lacked any evidence of peritonitis, rebound, or guarding. Goal-directed bedside ultrasound performed by the treating emergency physicians while awaiting laboratory testing revealed a live 9-week right interstitial pregnancy (Figures 1 and 2 and Video Clip S1, available as supporting information in the online version of this paper). Obstetrics was contacted immediately and arrangements were made to take the patient to surgery.

Figure 1.  Transabdominal sagittal view of interstitial pregnancy. The gestational sac is at the perimeter of the right edge of the uterus (Ut), and there is less than 5 mm of the myometrial mantle (seen as solid white line in image).

Figure 2.  Endovaginal sagittal view of interstitial pregnancy. The gestational sac is outside the endometrial echo of the uterus (Ut), and there is less than 5 mm of the myometrial mantle (seen as solid white line in image). EMS = endometrial stripe.

Ectopic pregnancy occurs in 1.9% of reported pregnancies and is the leading cause of pregnancy-related death in the first trimester.¹ Interstitial (or cornual) pregnancy is a rare type of ectopic pregnancy with an incidence of 0.7% to 4%; however, rupture occurs relatively early in pregnancy and is associated with severe hemorrhage and increased morbidity and mortality.¹ Timor-Tritsch and colleagues² proposed the following ultrasound criteria for diagnosis of interstitial pregnancy: “1) an empty uterine cavity; 2) a gestational sac located eccentrically and >1 cm from the most lateral wall of the uterine cavity; and 3) a thin (<5 mm) myometrial layer surrounding the gestational sac.” The supplemental video clip illustrates how goal-directed bedside ultrasound is a useful and noninvasive tool for the emergency physician in the diagnosis of ectopic pregnancy.