Ultrasound In Pregnancy
Ultrasound In Pregnancy
Transabdominal ultrasound (TAUS) and transvaginal ultrasound (TVUS) in the first-trimester pregnant patient is one of the primary applications of emergency ultrasound.1 Ectopic pregnancy has a prevalence of 8% in pregnant patients presenting to the ED34 and remains a top cause of maternal mortality.35 Unfortunately, approximately half of symptomatic ectopic pregnancies have no identifiable risk factors.36 Pelvic ultrasound performed by the emergency clinician can be both life-saving and time-saving in these patients.37-40 Emergency pelvic ultrasound can identify a definite diagnosis in the majority of symptomatic first-trimester pregnant patients and focuses on detection of an intrauterine pregnancy (IUP). Multiple studies have demonstrated pelvic ultrasound to be diagnostic of IUP or ectopic in approximately 70% to 75% of symptomatic first-trimester pregnant patients.40-42 In a study by Durham et al, pelvic ultrasound results obtained by emergency physicians were consistent with radiology department findings in 96% of cases (95% confidence interval [CI], 91% to 97%).41 A recent meta-analysis of emergency physician ultrasonography as a diagnostic test for ectopic pregnancy found that emergency physician-performed bedside ultrasonography demonstrated a sensitivity of 99.3% (95% CI, 96.6% to 100%) and a negative predictive value of 99.96% (95% CI, 99.6% to 100%) for detecting an intrauterine pregnancy.43
Focused Pelvic Ultrasound
Transabdominal ultrasound can identify an IUP in most women at 6 or 7 weeks’ gestation, while TVUS can identify an IUP 7 to 14 days earlier, at 5 to 6 weeks’ gestation.44 While TVUS scanning provides superior imaging of the uterus (ie, retroverted uterus) and adnexa, TAUS ultrasound offers a more global view of the pelvis, is easier to learn, and requires less maintenance from an infection-control perspective.34 (See Figure 4) For emergency clinicians, sonographic findings consistent with an IUP include a yolk sac, fetal pole, or fetal heart activity within the uterus, surrounded by an 8-mm rim of myometrium. (See Figure 5) Visualization of a yolk sac, whether by TAUS or TVUS, is the first definitive evidence of an IUP. Once an IUP has been confirmed, fetal viability (fetal heart rate) and gestational age can also be determined. Although visualization of an IUP does not completely exclude ectopic or heterotopic pregnancy, its presence — in patients without risk factors — decreases the chances sufficiently to allow for further outpatient management.34,38
Direct visualization of an ectopic pregnancy can be challenging, and is even more so when TVUS is not performed, since the most frequent finding in ectopic pregnancy is a complex adnexal mass.42 Although the emergency clinician may directly visualize an ectopic pregnancy, the focus of the scan is on assessing for an IUP (or lack thereof) or for the presence of free fluid in the hepatorenal space (Morison’s pouch) or the pelvic space (Pouch of Douglas). Transabdominal views of the right upper quadrant and pelvis are integral to ultrasound imaging of the symptomatic first-trimester pregnant patient. Although the presence of significant intraperitoneal fluid in a pregnant patient without a definite IUP is indirect evidence, it is suggestive of an ectopic pregnancy, and its detection can be life-saving.46
Length Of Stay In The Emergency Department And Cost-Effectiveness
Bedside TAUS and TVUS performed and interpreted by physicians have been shown to decrease ED lengths of stay. Blaivas et al performed a retrospective chart review identifying 1419 symptomatic first-trimester patients who had ultrasound examinations that confirmed live IUP.37 Lengths of stay for patients who received their pelvic ultrasound from emergency physicians were compared to those for patients who had studies performed by radiology staff. This study found that the median length of stay was 21% (59 minutes) less than those who received a pelvic ultrasound from radiology; this difference increased to 28% (1 hour and 17 minutes) during evening hours.
In a study by Burgher et al, the findings were similar and demonstrated that pelvic ultrasonography performed by emergency physicians saved an average of 60 minutes when compared with scans done by consultative services.47 Shih also assessed the effect of pelvic ultrasonography performed by emergency clinicians on length of stay and found that the time savings were significant when an IUP was detected.48 Durston et al evaluated the quality and cost-effectiveness of detecting an ectopic pregnancy with ultrasound in a single ED over a 6-year period. The study was divided into 3 similar time frames, with 3 different approaches to ultrasound availability: 1) limited availability of radiology staff-performed pelvic ultrasound, 2) readily available radiology staff-performed pelvic ultrasound, and 3) readily available emergency clinician-performed and radiology-staff performed pelvic ultrasound.49 This study found that the most cost-effective strategy is for emergency physicians to screen all patients with first trimester symptoms with emergency physician-performed pelvic ultrasounds and to obtain formal studies during the initial ED visit if the emergency physician-performed study is indeterminate. More specifically, Durston et al found that emergency physician-performed pelvic ultrasound saved 15.9 formal radiology studies and 9.7 ultrasound technician call-ins per ectopic pregnancy diagnosed.49
Pelvic ultrasound has been shown to be useful in the management of symptomatic first-trimester pregnant patients and is a core application of emergency ultrasound. Studies demonstrate that emergency physicians can make a definite diagnosis in the majority of such patients. When an IUP is identified, emergency physician-performed pelvic ultrasound has been shown to decrease length of stay. When indirect or direct evidence of an ectopic pregnancy is noted, emergency physician-performed pelvic ultrasound has been shown to expedite care and to be life-saving.
James Q. Hwang; Heidi Harbison Kimberly; Andrew S. Liteplo; Dana Sajed
March 2, 2011