Abdominal pain is one of the most common presenting complaints in the emergency department. The axiom “ectopic pregnancy is always the first consideration in a woman with abdominal pain” serves to remind the emergency physician that ectopic pregnancy is one of the important life-threatening causes of abdominal pain. Because making this determination generally changes the nature of the medical treatment, all other causes of abdominal pain in a woman of reproductive age should be considered only after the emergency physician rules out ectopic pregnancy as a cause.
Ectopic pregnancy is defined as any pregnancy in which implantation occurs at a location other than the endometrial lining within the uterine cavity.1 It is a common disease. Approximately 110,000 ectopic pregnancies are reported annually (CDC, 1992). The current incidence of an ectopic pregnancy is two percent of all pregnancies (CDC, 1995). This incidence has increased by a factor of three over the past 20 years. During this same period, there was an overall reduction in mortality. This decline is multifactorial, but probably stems from the development of the rapid qualitative BHCG test. Despite this reduction, ectopic pregnancy remains the leading cause of first trimester maternal deaths. It accounts for approximately 10 percent of all pregnancy-related deaths (CDC, 1995), and is the single most common cause of all pregnancy-related deaths in black women.2
Misdiagnosis remains a serious problem for ectopic pregnancy. The diagnosis of ectopic pregnancy is missed more than a third of the time at the first emergency department visit.3 Physicians may be confused by the often atypical presentation of ectopic pregnancy. History and physical exam are not always reliable. Symptoms and physical findings are often nondiscriminatory early in the course of ectopic pregnancy. Failure to diagnose ectopic pregnancy remains one of the leading causes of malpractice cases that emergency physicians face.4
Ectopic pregnancy most commonly results when ovum implants within the fallopian tube. The patient will initially be asymptomatic as the trophoblast erodes through the epithelium into the submucosa. Once the trophoblast erodes into the submucosal arterioles, a hematoma will develop causing tubal distention and pain. If the trophoblast does not die secondary to inadequate blood supply, it will continue to grow, causing increasing pain and bleeding.4 Mild and intermittent vaginal bleeding results from uterine decidual shedding caused by necrosis of the trophoblastic tissue.5
Risk factors for the development of an ectopic pregnancy include assisted reproduction, in vitro fertilization, tubal surgery or tubal occlusion, and DES exposure.3 Increases in rates of PID and assisted fertilization may account for the increased incidence in ectopic pregnancy seen over the past three decades. The presence of these risk factors may serve to heighten the clinician's suspicion for the diagnosis of ectopic pregnancy. However, it is important to remember that all pregnant woman are at risk for developing an ectopic pregnancy. Half of all ectopic pregnancies are diagnosed in women with no risk factors.
Diagnosis early in the course of the disease remains challenging. There are no signs or symptoms pathognomonic of an early ectopic pregnancy. Early symptoms are often vague and variable. The first complaint is often abdominal pain. Obviously, this carries an enormous number of possible diagnoses. Once the disease progresses and the patient develops the classic complaints of pain, bleeding, amenorrhea, and dizziness, the diagnosis becomes much more obvious. The patient has likely already developed complications.
While almost 100 percent of patients complain of pain, no type of pain is diagnostic. Early on, pain may be described as nonspecifically as “soreness” that progresses to a sharp and colicky pain. Location of the pain may even be diffuse, bilateral, or opposite of the involved side. Once rupture of the tube occurs, patients may experience a pain that is severe and lancinating. The presence of shoulder pain suggests that blood in the peritoneal cavity secondary to rupture is irritating the diaphragm.
Patients should be questioned regarding their recent menses. While 75 percent or more patients with ectopic pregnancy report amenorrhea, patients initially will often deny amenorrhea. Yet on further questioning, many will describe their most recent menses as lighter than usual. This menses may represent bleeding from an endometrial slough secondary the ectopic pregnancy.5
During physical examination of the patient, the clinician should focus on the assessment of hemodynamic status and the abdominal and pelvic exam. There is abdominal tenderness and adnexal tenderness in approximately half of women presenting with ectopic pregnancy.4 While the presence of these physical findings may help to support the diagnosis of ectopic pregnancy, the absence of these findings certainly does not rule it out. Furthermore, certain classic findings may be of no help in the diagnosis. Only half of patients with an ectopic pregnancy have a palpable adnexal mass. However, 20 percent of these patients have a mass on the side opposite the ectopic, usually a corpus luteum cyts.5 Uterine size also can be misleading. While the majority of patients have a normal size uterus, as many as 30 percent of patients have an enlarged uterus of six-week size or greater.4
Differential diagnoses include PID, ovarian torsion, spontaneous abortion, or gastroenteritis. Up to 20 percent of patients with ectopic pregnancy have temperatures elevated to 100.4°F, and slightly less than 10 percent will have a temperature greater than 100.4°F. Consequently, ectopic pregnancy is frequently misdiagnosed as PID. PID rarely occurs during pregnancy, and physicians should be wary of making this diagnosis without sufficiently ruling out ectopic pregnancy.3,5
Any woman of reproductive age who presents with abdominal pain should undergo qualitative beta sub-unti human chorionic gandotropin (BHCG) testing to evaluate for the possibility of pregnancy. Clinical diagnosis is no more accurate than the flip of the coin in predicting the presence of ectopic pregnancy.5 There can be no doubt that the rapid bedside pregnancy test has revolutionalized the care of the ectopic pregnancy. Many women were mistakenly diagnosed with PID or other abdominal conditions for the lack of this test.
An early diagnosis is more amenable to methotrexate than the surgical intervention required in larger, more complicated ectopic pregnancies
If a BHCG test is negative, ectopic pregnancy can be effectively ruled out as a cause of the abdominal pain. Remember, the qualitative assays can detect BHCG as low as 10 to 20 mIU/ml. If the test is positive, quantitative serum bhCG testing should be performed, but the absolute value of a single BHCG level will not indicate the location of the pregnancy. However, quantitative BHCG can be helpful in conjunction with ultrasound to determine the diagnosis. Furthermore, it is needed as a baseline for serially testing in stable patients undergoing observation or in methotrexate-treated patients.
Any woman with abdominal pain and a positive pregnancy test should undergo diagnostic testing by ultrasound regardless of BHCG levels. While in a normal intrauterine pregnancy the bhCG level roughly doubles every two days, this is not the case in an ectopic pregnancy. The level may rise normally but more often rises at a slower rate due to impaired production of BHCG.6 An intrauterine pregnancy can be visualized using a transvaginal transducer when the BHCG is between 1200–1500 mIU/ml. This is referred to as the discriminatory zone.7
Strategies to eliminate the pelvic ultrasound when the BHCG is below the discriminatory zone are flawed without full consideration of the clinical picture. Ectopic pregnancies can rupture in apparently stable patients with quantitative BHCGs this low. When quantitative BHCGs are above the discriminatory zone and no intrauterine pregnancy is visualized, an ectopic pregnancy is highly likely.8 While the diagnosis can only be confirmed if a sac is visualized outside the uterus, failure to see an extrauterine pregnancy never rules out an ectopic pregnancy.
The presence of an intrauterine pregnancy has been presumed to exclude the existence of an ectopic pregnancy. However, a heterotopic pregnancy could still be present. In this condition, a coexisting ectopic pregnancy and intrauterine pregnancy are present. The incidence of heterotopic pregnancy has been traditionally reported as one in 30,000. This value was calculated in 1948 by multiplying the ectopic pregnancy rate by the dizygotic twin rate. Because the rates of ectopic pregnancy have increased by a factor of six since that time, the current estimates are approximately one in 5000.1 Among women undergoing ovulation induction, the incidence may be as high as one in 35.7. Therefore, proof of an IUP in high-risk patients or in patients without a convincing clinical picture may not rule out ectopic pregnancy.
An early diagnosis is more likely to be amenable to medical therapy with methotrexate rather than the surgical intervention required in larger and more complicated ectopic pregnancies. Surgery and anesthesia possess a certain degree of irreducible morbidity and risk of mortality.6 Use of methotrexate therapy would avoid these added risks. Methotrexate therapy may be used only in hemodynamically stable patients with an unruptured ectopic pregnancy measured by ultrasound to be less than 4 cm in diameter or 3.5 cm in diameter with cardiac activity.1
Missing an early ectopic pregnancy may jeopardize future reproductive capabilities in addition to increasing the morbidity and mortality of patients. If surgical intervention is required, an earlier diagnosis is more likely to permit the use of tubal conservation procedures. Salpingostomy as opposed to salpingectomy has become the standard operation in an unruptured ectopic pregnancy measuring larger than 4 cm. Earlier diagnosis will more often allow laparoscopy rather than laparotomy — the latter carries significantly more complications.6
Early diagnosis is crucial to avoiding complications of ectopic pregnancy. Only with heightened awareness can the emergency physician diagnose ectopic pregnancy early in the course of the disease. The earlier the diagnosis is made, the more likely intervention can take place prior to rupture of the tube and accompanying hemorrhage and possible death. Because the determination of pregnancy in a woman of childbearing age with abdominal pain is often the pivot point for management of the case, we believe that ectopic pregnancy is always the first consideration in a woman of reproductive age with abdominal pain. The emergency physician who adheres to this axiom will likely preserve not only the patient's health but her future fertility.