a b s t r a c t

Objective: The objective was to determine if the need for Transvaginal ultrasonographic examination can be de- creased by the addition of the transabdominal high-frequency, 12-4-MHz linear transducer after a failed exam- ination with the 6-2-mHz curvilinear transducer when evaluating for an Intrauterine pregnancy (IUP).

Methods: This is a prospective pilot study of women in their first trimester of pregnancy presenting to the emer- gency department with abdominal pain and/or Vaginal bleeding. If no IUP was identified using the curvilinear transducer via the transabdominal approach, they were subsequently scanned using the linear transducer. Pa- tients without evidence of an IUP transabdominally were scanned via the transvaginal approach.

Results: Eighty-one patients were evaluated; no IUP was visualized in 27 using the standard curvilinear transduc- er approach, and these then had an ultrasonography performed with the linear transducer. Of these, 9 patients (33.3%; 0.95 confidence interval [CO], 15.5%-51.1%) were found to have an IUP with the linear transducer. For the 18 patients who received a transvaginal scan, 15 patients (83.3%; 0.95 CI, 66.1%-100%) had no IUP identified with the transvaginal transducer, and 3 (16.7%; 0.95 CI, 0%-33.9%) had an IUP identified.

Conclusions: The transabdominal use of a high-frequency linear transducer in the evaluation of patients in the first trimester after failed curvilinear transducer results in a clinically significant reduction in the need for transvaginal ultrasonography to confirm the presence of an IUP.

(C) 2015

Introduction

Ectopic pregnancy is the leading cause of death in the first trimester of pregnancy [1] and is a feared complication in women in early pregnancy who present with abdominal pain, pelvic pain, or vaginal bleeding. The rate of ectopic pregnancy in the general population is approximately 1.5% to 2% of pregnancies with a Maternal mortality of 6% to 9% [2,3]. However, in symptomatic women presenting to the emergency depart- ment (ED), the rate of ectopic pregnancy has been demonstrated to be as high as 13% [4]. Pelvic ultrasonography is the Diagnostic modality of choice in ectopic pregnancy [3,5]. In the evaluation of the symptomatic First-trimester pregnancy, studies have shown that transabdominal and transvaginal ultrasonography performed and interpreted at the bedside by emergency physicians has a high sensitivity and high negative predic- tive value, effectively ruling out ectopic pregnancy by affirmatively visual- izing an intrauterine yolk sac or Gestational sac [6,7].

The primary focus of pelvic ultrasonography in the ED is the detec- tion of an intrauterine pregnancy (IUP) [8]. The American College of Ra- diology, American College of Obstetrics/Gynecology, American Institute of Ultrasound in Medicine, Society of Radiologists in Ultrasound (ACR-

* Corresponding author at: 2500 MetroHealth Dr BG-3, Cleveland, OH 44109.

E-mail address: [email protected] (M. Tabbut).

ACOG-AIUM-SRU) joint guidelines in the evaluation of obstetrical ultra- sonography indicate that pelvic ultrasonography can be performed transabdominally or transvaginally [9]. Although a comprehensive ul- trasonography requires a detailed evaluation of the uterus and adnexa, a limited study can be performed to answer the specific question of whether there is an IUP. Thus, usual care in our department for the eval- uation of the symptomatic first-trimester patient begins with transAbdominal ultrasonography. Equivocal or negative studies are followed up transvaginally.

Transvaginal ultrasonography, in addition to being invasive, is time consuming and requires particular disinfection after scanning and may not be ubiquitously available in community EDs. All are potential limita- tions to its use at the bedside in clinical practice. Prior anecdotal experience in our department has shown that the transabdominal use of the high- frequency linear transducer has been effective at confirming an early IUP after an equivocal or negative evaluation using the curvilinear transducer. To date, there are no known prospective studies evaluating the use of the linear transducer in the detection of early first-trimester pregnancy.

Materials and methods

We conducted a single-center, prospective, convenience, pilot sample of women in their first trimester of pregnancy presenting to the ED and

http://dx.doi.org/10.1016/j.ajem.2015.11.001

0735-6757/(C) 2015

M. Tabbut et al. / American Journal of Emergency Medicine 34 (2016) 288–291 289

undergoing bedside ultrasonography for the detection of an IUP. Patients were included if they had a positive pregnancy test in the ED and had not received prior fetal imaging during the current pregnancy. The study was approved by the hospital’s Institutional Review Board, and informed con- sent was obtained before scanning.

The study was performed in a large, urban, academic ED with an an- nual volume of more than 100,000 patients per year with an established emergency ultrasonography fellowship. The majority of the images were obtained by the ultrasonography fellow or emergency medicine residents under the direct supervision of the department’s ultrasonog- raphy educator, a registered diagnostic medical sonographer dedicated to the ED. The study was primarily completed during the hours of 8:00

AM to 5:00 PM because of the presence of our ultrasonography team, but

participants were eligible to be enrolled at any time if a member of the study was clinically available.

Transabdominal scanning was performed with either a Philips HD11 (Bothell, WA) or 1 of 2 Philips Sparq (Bothell, WA) machines which are used in regular clinical practice in our ED. Imaging presets and settings were set at the bedside at the discretion of the imaging team. Sonographically, an IUP was defined by the presence of a yolk sac and/ or fetal pole within a gestational sac in the uterus.

Patients enrolled were first scanned using the standard curvilinear transducer (5-2 mHz for HD11 or 6-2 mHz for Sparq) via the transabdominal approach in both the sagittal and transverse planes. If no IUP was identified, they were subsequently scanned using the linear transducer (12-3 mHz for HD11 or 12-4 mHz for Sparq) in a similar fashion. Patients without evidence of an IUP transabdominally by curvi- linear or linear transducer were subsequently scanned via the transvaginal approach by radiology or supervised by an emergency phy- sician privileged in transvaginal ultrasonography (Fig. 1). All images were reviewed by the ultrasonography fellow.

Measurements were obtained from clinical images in either the sag- ittal or transverse orientation based on image clarity. When seen, a crown-rump length (CRL) measurement was obtained, and machine- based imaging software calculated the gestational age based on CRL. In many images, only a yolk sac was visualized, and no CRL measure- ment was obtained. The depth to IUP was measured post hoc as the deepest distance from the transducer to the anteriormost surface of the yolk sac or fetal pole.

As a pilot study, data are reported as percentage with a confidence in- terval (CI) of proportion. Confidence intervals were calculated using the online calculator found at http://www.mccallum-layton.co.uk/tools/ statistic-calculators/confidence-interval-for-proportions-calculator.

Fig. 1. Scanning protocol for symptomatic first-trimester patients. Total numbers shown with percentages indicated.

Results

A total of 88 patients were enrolled that met the inclusion criteria. Seven patients were excluded because incomplete data were obtained. The remainder were scanned as shown in Fig. 1. Of the 81 patients in- cluded in this study, no IUP was visualized in 27 (33.3%; 0.95 CI, 23.0%-44.6%) using the standard curvilinear transducer approach, and these then had an ultrasonography performed using the linear trans- ducer. One patient was found to have an ectopic pregnancy on curvilin- ear transducer and was included in the 54 patients with visualized pregnancy. Of the 27 patients requiring linear ultrasonography, 9 pa- tients (33.3%; 0.95 CI, 15.5%-51.1%) were found to have an IUP with the linear transducer. The linear ultrasonography did not identify an IUP in 18 (66.7%; 0.95 CI, 48.9%-84.5%). For the 18 patients, 15 patients (83.3%; 0.95 CI, 66.1%-100%) had no IUP identified with the transvaginal transducer, and 3 (16.7%; 0.95 CI, 0%-33.9%) had an IUP identified. The linear transducer was able to detect an IUP on 33.3% of the patients in whom it was used. The number needed to treat is 3. The combined fail- ure rate of curvilinear and linear transducer was 18 (22.2%; 0.95 CI, 13.2%-31.3%) of 81 patients (Table 1).

Serum human chorionic gonadotropin levels were obtained for patients with no IUP identified for all 3 scanning modalities and are presented in Fig. 2.

The data comparing depth to pregnancy for patients with pregnancy identified based on curvilinear transabdominal or linear transabdominal approach are displayed in Table 2.

Discussion

Identification of an IUP in the symptomatic first-trimester patient in the ED is of paramount importance. Ectopic pregnancy is a feared com- plication of patients in the first trimester with a high mortality if unde- tected. Ultrasonography is the standard method for evaluating symptomatic patients in the ED. As such, a limited ultrasonography of the pelvis, particularly focused on the identification of an IUP, is a safe and cost-effective means to evaluate symptomatic patients in the ED, and further comprehensive imaging can be obtained as an outpatient.

Previous study protocols have used both transabdominal curvilinear and/or transvaginal transducers [5,10]. As a less invasive technique, the curvilinear transabdominal transducer is used initially in the evaluation of the pelvis for the presence of an IUP. However, this is often limited by the resolution of the low-frequency transducer, particularly early in pregnancy (Fig. 3). Anecdotally, in our practice, we have found the dis- criminatory threshold for our transabdominal curvilinear transducer to be approximately 6-7 weeks of gestational age. Below this age, addition- al image is often necessary to identify the location of the pregnancy.

The next evaluation for patients with inconclusive transabdominal ultrasonography is a transvaginal ultrasonographic examination. Stud- ies have shown that a limited transvaginal ultrasonography can success- fully be performed by emergency physicians [5,10]. However, emergency physician-performed transvaginal ultrasonography is often limited by equipment, time, and/or training. When not performed by emergency physicians, transvaginal ultrasonography is accom- plished by radiology. This addition of comprehensive pelvic evaluation may be limited by staffing availability and adds to the patient’s ED length of stay [11].

Table 1

UltraSonographic findings based on transducer used Results of ultrasonographic imaging

		CTA	LTA	TV
	IUP	54	9	3
	No IUP	27	18	15

CTA, curvilinear transabdominal; LTA, linear transabdominal; TV, transvaginal.

290 M. Tabbut et al. / American Journal of Emergency Medicine 34 (2016) 288–291

Fig. 2. The HCG levels of patients with no IUP Identified.

As a higher-frequency transducer, the linear transducer can provide greater resolution of smaller structures as compared with the curvilinear transducer (Fig. 4). This study looked at the impact of using the linear transducer in the identification of an IUP after a negative or indeterminate evaluation with the curvilinear transducer.

Previous literature reports a failure rate to identify an IUP on bedside ultrasonography of approximately 20% using curvilinear and/or transvaginal ultrasonography [5]. In our study, we found a failure rate of 33.3% for the curvilinear transabdominal transducer. When combined with the linear transducer, the failure rate was decreased to 22.2%, sim- ilar to the values previously reported for the combination of curvilinear and transvaginal transducers. We found that 33.3% of the cases that would have been scanned transvaginally had an IUP identified with the linear transducer via the transabdominal approach. Thus, we showed that, in the cohort of women who require transvaginal ultraso- nography, we were able to decrease this number by 33.3%. The number needed to treat (NNT) for this cohort is 3 patients. In addition, only 3 pa- tients who had no IUP identified with the linear transducer were ulti- mately found to have an IUP identified with Transvaginal sonography. The vast majority of patients (83.3%) who received a transvaginal ultra- sonography had findings that were concordant with the linear trans- ducer. Based on the average serum HCG levels, these were presumed to be too early to detect sonographically.

Although transvaginal ultrasonography is widely used in the com- prehensive evaluation of the uterus and adnexa, this modality may not be available in nonacademic EDs where emergency physician- performed transvaginal sonography is limited by training, credentialing, or transducer availability. In addition to these factors, radiology- performed transvaginal ultrasonography may also be limited by avail- ability of sonographers, particularly after hours.

We believe the use of the linear transducer to be an important addi- tion in the workup of the symptomatic first-trimester patient. We have

Table 2

Deepest distance from the transducer to the anteriormost surface of the yolk sac or fetal pole

	Depth to identified pregnancy
	Distance (cm)	CTA	LTA
	Average	5.3	3.9
	Min	3.2	3.2
	Max	8.1	4.1

shown that our ability to identify an IUP transabdominally with the addi- tion of the linear transducer is comparable to that previously reported for transvaginal sonography. Thus, the linear transducer can be effectively used after failed curvilinear sonography to identify the presence of an IUP.

Fig. 3. Transabdominal curvilinear images: (a) sagittal uterus and (b) transverse uterus images show an anechoic intrauterine sac with no yolk sac or fetal pole.

M. Tabbut et al. / American Journal of Emergency Medicine 34 (2016) 288–291 291

Fig. 4. Transabdominal linear image in the same patient shows anechoic intrauterine sac with yolk sac confirming IUP.

There are limitations to the use of the linear transducer. First, as a high-frequency transducer, beam penetration is forfeited for resolution. As such, the linear transducer will have a more difficult time evaluating deeper structures or providing adequate penetration in obese patients. In our study, we had an average depth to IUP discovered using the linear transducer of 3.9 cm. Our study was not designed to detect a depth threshold for the linear transducer.

Second, our protocol did not use the linear transducer to provide a comprehensive evaluation of the adnexa. Our primary end point was the visualization of an IUP. As a screening modality, a limited pelvic ul- trasonography is sufficient to identify the presence of an IUP [8] in the absence of heterotopic risk factors. Therefore, based on our data, the lin-

ear transducer will not supplant a transvaginal ultrasonography for a comprehensive evaluation of the uterus and adnexa.

Conclusion

The transabdominal use of a high-frequency linear transducer in the evaluation of patients in the first trimester after failed curvilinear trans- ducer results in a clinically significant reduction in the need for transvaginal ultrasonography to confirm the presence of an IUP.

References

1. Current trends ectopic pregnancy–United States, 1990-1992. CDC MMWR Morb Mortal Wkly Rep 1995;44:46-8 [http://www.cdc.gov/mmwr/preview/mmwrhtml/ 00035709.htm. Accessed January 12, 2015].
2. Barnhart KT. Ectopic pregnancy. N Engl J Med 2009;361:379-87.
3. Adhikari S, Blaivas M, Lyon M. Diagnosis and management of ectopic pregnancy using Bedside transvaginal ultrasonography in the ED: a 2 year experience. Am J Emerg Med 2007;25:591-6.
4. Kohn MA, Kerr K, Maklevich D, O’Neil N, Kerr JM, Kaplan BC. Beta-human chorionic gonadotropin levels and the likelihood of ectopic pregnancy in emergency depart- ment patients with abdominal pain or vaginal bleeding. Acad Emerg Med 2003; 10:119-26.
5. Tayal VS, Cohen H, Norton J. Outcome of patients with an indeterminate emergency department first-trimester pelvic ultrasound to rule out ectopic pregnancy. Acad Emerg Med 2004;11:912-7.
6. Stein JC, Wang R, Adler N, et al. Emergency physician ultrasonography for evaluating pa- tients at risk for ectopic pregnancy: a meta analysis. Ann Emerg Med 2010;56:674-83.
7. Shih CH. Effect of emergency physician-performed pelvic sonography on length of stay in the emergency department. Ann Emerg Med 1997;29:348-52.
8. American College of Emergency Physicians. emergency ultrasound guidelines. Approved October 2008 http://www.acep.org/Clinical–Practice-Management/Emergency-Ultra- sound-Guidelines–2008/? taxonomyid=117952. [Accessed January 12, 2015].
9. American Institute of Ultrasound in Medicine. AIUM practice guidelines for the perfor- mance of obstetrical ultrasound examinations. J Ultrasound Med 2013;32:1083-101.
10. Blaivas M, Sierzenski P, Plecque D, Lambert M. Do emergency physicians save time when locating a live intrauterine pregnancy with bedside ultrasonography? Acad Emerg Med 2000;7:988-93.
11. MacVane CZ, Irish CB, Strout TD, Owens WB. Implementation of transvaginal ultra- sound in an emergency department residency program: an analysis of resident in- terpretation. J Emerg Med 2012;43:124-8.