Abdominal pain and vaginal bleeding are common complaints of patients presenting to the Emergency Department (ED) in the first 20 weeks of pregnancy. These patients account for about 1% of all ED visits. One in every 13 women presenting with these symptoms to the ED during early pregnancy will eventually be diagnosed with an ectopic pregnancy.1–5 History and physical examination have proven to be unreliable in excluding the presence of an ectopic pregnancy. Pelvic ultrasound (US) is the diagnostic test of choice in the initial evaluation of these patients with possible ectopic pregnancy.
Emergency Physicians have been using bedside pelvic US in the evaluation of first-trimester pregnancy symptoms for more than a decade. Prior studies have demonstrated that ED pelvic US decreases cost, patient length of stay, and morbidity.6,7 The goal of ED US is to identify an intrauterine pregnancy (IUP). An IUP is identified 60% to 70% of the time on bedside US in women presenting with abdominal pain and/or vaginal bleeding to ED.8 The accuracy of pelvic US performed by Emergency Physicians for identifying an IUP has been well established.9,10 With increasing experience, the scanning skills of Emergency Physicians have extended beyond just identifying an IUP. Recent studies have shown that Emergency Physicians can accurately diagnose ectopic pregnancy using bedside US.11
The pelvic cavity extends from the iliac crests superiorly to the pelvic diaphragm inferiorly. The female pelvis consists of the genital tract (vagina, uterus, and uterine tubes), ovaries, the urinary bladder, a portion of the ureters, the lower intestinal tract, pelvic musculature, ligaments, and peritoneal spaces.
The uterus is an oval, hollow, muscular, and pear-shaped extraperitoneal organ located in the pelvis between the urinary bladder anteriorly and the rectum posteriorly (Figure 130-1). It is divided anatomically into the fundus, the body, the isthmus, and the cervix. The central cavity of uterus opens into a fallopian tube on either side and into the vagina below. The uterus is usually anteverted (uterus pointing forward toward the anterior abdomen) and anteflexed (flexed forward over the bladder). It may, however, be retroverted (uterus pointing back toward the spine) and retroflexed (flexed away from the bladder) in some patients. The long axis of the uterus rarely lines up exactly with the long axis of the body. Most often it is found angled to one side. The size of the uterus is variable depending on the patient's parity, pubertal stage, and age. A postpubertal adult female uterus is approximately 8 cm long, 5 cm wide, and 3 cm deep. The endometrial canal is formed by the central, linear, and opposing surfaces of the endometrial cavity. The endometrial canal continues as the endocervical canal inferiorly. The vagina extends from the cervix to the external genitalia and lies between the urinary bladder and the rectum (Figure 130-1A).