The Use of Ultrasonography in the Diagnosis of Ectopic Pregnancy: A Case Report and Review of the Literature

Abstract

Ectopic pregnancy is still the most common cause of maternal deaths in the first trimester. Here we report a case of a 29-year-old pregnant woman who presented with a 2-week history of lower abdominal pain and vaginal bleeding. She was initially diagnosed as having had a complete miscarriage. On the second presentation the patient was diagnosed with a tubal ectopic pregnancy. The patient was managed surgically and recovered uneventfully. The case is discussed, and a review of the literature in relation to the use of ultrasonography in the diagnosis of ectopic pregnancy is presented.

Introduction

An ectopic pregnancy is an extrauterine pregnancy. The most common site for implantation is the fallopian tube; however, the conceptus may implant in the ovaries, the cervix, or the abdomen.[1,2] Ectopic pregnancy was the fourth most common cause of maternal death in the most recent Confidential Enquiry into Maternal Deaths (CEMD) in the United Kingdom 2000–2002, accounting for 73% of early pregnancy deaths.[3] Furthermore, it is still the most common cause of maternal deaths in the first trimester.[4] Two thirds of women who died from ectopic pregnancy were misdiagnosed in primary care or Accident and Emergency.[3]

Case Report

A 29-year-old gravida 4, para 3 woman presented to the emergency gynecology assessment service with a 2-week history of lower abdominal pain and vaginal bleeding, passing large clots. Her last menstrual period had been 5 weeks prior to presentation. Her urinary beta-hCG test was positive. An ultrasound scan (USS) showed an empty uterus and there were no adnexal masses. She was told that she had had a complete miscarriage and was discharged. She returned 6 days later with severe lower abdominal pain and right-sided iliac fossa pain, radiating all over the abdomen. A USS found an adnexal mass in her right fallopian tube. She had a laparoscopic salpingectomy for a right tubal ectopic pregnancy. The patient was started on antibiotics and recovered successfully.

Discussion

An ectopic pregnancy is a potentially life-threatening gynecologic emergency that requires urgent intervention. Because the vast majority of ectopic pregnancies are tubal,[1] this discussion concentrates on this specific type of ectopic pregnancy. There is ongoing debate in regard to the best method to investigate and diagnose (tubal) ectopic pregnancy.[2]

In all sexually active women of reproductive age who present with lower abdominal pain, with or without vaginal bleeding, an ectopic pregnancy must be excluded. A qualitative urine dipstick test for beta-hCG (urinary pregnancy test) must be carried out.[4,5] This is a quick, easy, and sensitive test. It has a sensitivity of 99% at a urine beta-hCG level greater than 25 IU/L.[4] If a woman has a negative urinary pregnancy test, this almost invariably means that she does not have an ectopic pregnancy.[4] However, if it is positive the woman should have a USS.[4,5]

Gracia and Barnhart[6] compared different methods of diagnosing ectopic pregnancy using combinations of transvaginal ultrasound plus biochemistry (serum progesterone and serum beta-hCG), ultrasound only, and clinical examination without ultrasound. The study found that the most accurate method of diagnosing ectopic pregnancy was using a combination of ultrasound followed by beta-hCG.

A recently published review by Sawyer and Jurkovic[2] found that the most accurate way to diagnose an ectopic pregnancy is the use of a combination of ultrasonography, serum beta-hCG, and histology, either following laparoscopy or dilatation and curettage (D&C). However, unlike ultrasonography, neither biochemistry nor histology are available immediately, and when presented with a pregnant woman with pain and/or vaginal bleeding, clinicians must urgently exclude an ectopic pregnancy. As such, the initial investigation should be ultrasonography.

In addition to having a transabdominal ultrasound scan, a symptomatic woman with a positive urinary pregnancy test should also have a transvaginal ultrasound scan (TVS) performed. The use of TVS in the diagnosis of ectopic pregnancy has become widely accepted and practiced. Transvaginal ultrasonography has transformed the assessment of problems in early pregnancy.[5] It is suggested that transvaginal ultrasonography is the “ultimate diagnostic tool” in the diagnosis of ectopic pregnancy.[7] In fact, Condous upholds that “transabdominal ultrasonography is an outdated modality which is not diagnostic of ectopic pregnancy and should no longer be used.[4]” However, transabdominal scans are still very informative because TVS can miss some suprapubic pathology. Comparing the 2 ultrasonographic modalities, it has been said that the diagnostic reliability of transabdominal ultrasonography is around 70%, whereas that of TVS, under ideal conditions, is more than 90%.[8]

Shalev and colleagues[7] found that the use of TVS in the diagnosis of an ectopic pregnancy has a sensitivity of 87%, specificity of 94%, and positive predictive value of 92.5%. Another study[9] gave a sensitivity of 93%, specificity of 99%, and positive predictive value of 98%, and when a TVS finding of an adnexal mass was combined with serum beta-hCG, this increased the sensitivity to 97%, with equivalent specificity and positive predictive value.

The possible adnexal findings on USS in an ectopic pregnancy are[1,10]:

• A tubal ring, ie, an empty gestational sac;

• A gestational sac with a fetal pole and fetal heartbeat;

• A gestational sac containing a yolk sac or embryo; and

• An adnexal mass other than a simple cyst.

A retrospective study[11] of ultrasonographic images found that a tubal ring (an adnexal mass with a concentric echogenic rim of tissue [a gestational sac] surrounding a hypoechoic [empty] center) was present in 68% of ectopic pregnancies in which the tube had not ruptured. Brown and Doubilet[10] identified the 4 aforementioned ultrasonographic findings for the diagnosis of ectopic pregnancy. They concluded that the most appropriate way to identify an ectopic pregnancy is with any noncystic adnexal mass. However, it must be noted that the absence of adnexal findings on TVS does not exclude an ectopic pregnancy, and serial serum beta-hCG levels should be measured.[1]

Occasionally a “pseudosac” may be seen in the uterus (Figure 1). This is an intrauterine fluid collection produced by the ectopic pregnancy, which can mimic a gestational sac giving a false picture of an intrauterine pregnancy.

Figure 1.

Transvaginal ultrasound scan showing a pseudosac in the uterus (black arrow) with a live ectopic pregnancy in the adnexa (white arrow).

Sometimes there are no conclusive adnexal findings, and the diagnosis of ectopic pregnancy may be based on other ultrasound features, such as hematoperitoneum,[2,12] hematosalpinx,[2,12] and free fluid in the peritoneum or the pelvis, for example, in the pouch of Douglas (Figure 2).[12]

Figure 2.

Transvaginal ultrasound scan showing an empty uterus (short white arrow, pointing toward the thin white horizontal linear shadow, the endometrium) and a mass in the pouch of Douglas (black arrow) with some free fluid (long white arrow).

The diagnosis of ectopic pregnancy should be based on the positive findings of an adnexal mass with TVS rather than the absence of an intrauterine gestational sac (ie, an “empty uterus”).[4] The CEMD report describes a potentially preventable death in which a woman who had an empty uterus on USS was misdiagnosed with complete miscarriage. She died 3 weeks later.[3] The differential diagnosis of an empty uterus with a positive beta-hCG is complete miscarriage, an early pregnancy (less than 5 weeks), or ectopic pregnancy.[1]

Ultrasound reports that read “empty uterus, ectopic pregnancy cannot be excluded” are not helpful.[4] If an ectopic pregnancy is present and scanning skills are highly developed, between 87% and 93% should be identified with TVS before surgery.[7,9,13] If there are no adnexal findings on TVS in the absence of an intrauterine gestational sac, then ectopic pregnancy must still be excluded, by measuring serial serum beta-hCG levels.[4,5]

Conclusion

Diagnosing ectopic pregnancy earlier with TVS has changed the available management options. Early diagnosis allows the clinician to consider conservative options, such as methotrexate, in patients who are hemodynamically stable and in whom the ectopic pregnancy is small.[1,14] It has also reduced the associated mortality, with shock and collapse and subsequent emergency laparotomy being the exception rather than the rule in modern practice.[4] The use of TVS in the diagnosis of ectopic pregnancy has meant that laparoscopy can be reserved for its treatment, rather than as a diagnostic tool.[2]

The reported case highlights an example of a situation in which an ectopic pregnancy was inadequately excluded and a misdiagnosis of a complete miscarriage was made. The error that was made is that an ectopic pregnancy was excluded on the basis of the lack of any adnexal masses on TVS and the absence of an intrauterine gestational sac.

As stated above, the lack of adnexal masses on TVS does not rule out the presence of an ectopic pregnancy. An empty uterus with a positive urinary beta-hCG is not diagnostic of a complete miscarriage. Both findings, as this case illustrates, do not eliminate the possibility of an ectopic pregnancy. Therefore, women with suspected complete miscarriages in whom ectopic pregnancy cannot be excluded must be followed up by close monitoring of their serial serum beta-hCG levels.

On the basis of this review, the following management algorithm is recommended to evaluate a sexually active woman of reproductive age who presents with lower abdominal pain and/or vaginal bleeding for the possibility of an ectopic pregnancy. First, a beta-hCG urine dipstick test must be performed urgently. If this is positive, she must have a USS. If there are adnexal masses suggestive of an ectopic pregnancy, she must be treated for this. However, even if there are no adnexal masses on TVS, in the absence of an intrauterine gestational sac ectopic pregnancy cannot be excluded, and she must have serial serum beta-hCG measurements.[4,5]