Of the 96% of EPs found in the fallopian tube, 70% are ampullary, 12% isthmic, 11% fimbrial, and 2% interstitial, with extratubal sites being rare (5) (Fig. 3.1). The tube serves a complex function in the process of fertilization and transport of the oocyte from the ovary to the uterus, where the blastocyst implants. At ovulation, the fimbriated end of the fallopian tube picks up the expelled oocyte with its cumulus mass of follicular cells. Conduction of the egg toward the uterus is thought to be effected primarily by the negative tubal intraluminal pressure generated by muscular contractions, with a secondary contribution from ciliary beating. Impaired muscular contractions, loss of ciliary action, or physical blockade could therefore prevent the embryo from reaching its normal location in the uterus. Tubal transport takes approximately 3 days, with fertilization occurring in the ampullary portion of the tube. Damage to the tube from prior infection, surgery, or tubal pregnancy can therefore subsequently increase one’s risk of future EP (6,7,8) (Table 3.1). A woman who experiences one EP has an increased risk of a second; women with an EP are 2.4 to 25 times as likely to have had a prior EP (8).

Although any form of contraception decreases the overall risk of pregnancy including EP, when contraceptive failure occurs in women using an intrauterine device (IUD) or following tubal sterilization, the risk of EP is elevated (7,9). With the copper T, approximately 6% of failures represent ectopic implantations (10). With the levonorgestrel IUD, this percentage is approximately 50 (11). Other factors in the history which may be associated with risk of EP include a history of salpingitis, tubal infertility, and DES exposure (6,7).

Among patients presenting to the emergency room with an early symptomatic pregnancy, the incidence of EP was lower for adolescents than adults (9.7% versus 21.7%) (12) and younger women (<25 years old) (8). However,
adolescents with EP present more often than adults with pain and a positive chlamydia and/or gonorrhea culture and less often with the classic risk factors of prior EP and prior pelvic surgery (12).

Although the classic signs and symptoms of EP are pain, amenorrhea, and vaginal bleeding, this diagnosis should be suspected in any reproductive-age woman presenting with pain or abnormal bleeding, as well as in women with symptoms of shock. The character of the pain is often nonspecific and may be diffuse, unilateral, bilateral, or even contralateral to the side involved. In tubal pregnancies, the pain may begin as vague lower abdominal discomfort that later becomes sharp and colicky as periodic tubal distention occurs. By contrast, the pain associated with the spontaneous abortion of an IUP is usually central and is likened to that of labor or menstrual cramps. Tubal rupture may be accompanied by a significant hemoperitoneum, resulting in poorly localized abdominal pain. Shoulder pain is possible secondary to phrenic nerve irritation when blood contacts diaphragmatic surfaces.

Although a history of recent amenorrhea is common in women with EPs, it is not unusual for a patient initially to deny having missed any menstrual periods. On a careful review, however, the most recent period may be described as lighter or abnormally timed, perhaps representing pathologic bleeding from decidualized endometrium. The abnormal vaginal bleeding reported by women with EPs is usually mild. Heavy bleeding or passage of clots is distinctly atypical and is more characteristic of inevitable or incomplete abortion of an IUP.

Factors in the patient’s history may increase the physician’s suspicion for EP. Questions regarding prior tubal surgery, pelvic infections, history of infertility, and type of birth control are appropriate. Current data indicate an ectopic rate for conceptions after the use of assisted reproductive technologies (ARTs) comparable to the estimated incidence of EP in the United States of 2% (13), but one third of conceptions resulting from sterilization are EPs (14). A history of induced or spontaneous abortion does not eliminate the possibility of an EP.

It should be stressed that history and physical findings, although necessary and important for assessing the patient and planning the appropriate follow-up and treatment, are not sufficient for exclusion or confirmation of an EP diagnosis (7). It should also be noted that whereas certain elements of the history may be more suggestive of a spontaneous abortion, such as heavy bleeding, passing of tissue, or midline cramping, they can also be found in some patients ultimately found to have an EP (7). Ultrasound in conjunction with human chorionic gonadotropin (hCG) levels may provide a definite diagnosis, and in stable patients in whom the diagnosis is uncertain, close follow-up is warranted.

The clinical presentation of a patient with an EP can mimic a number of other gynecologic and nongynecologic disorders (Table 3.2). Because most of these disorders are not immediately life threatening, it is important that the clinician excludes EP when considering these and other conditions in a woman of reproductive age with abdominal pain or abnormal bleeding. In addition, EP must be immediately suspected in a woman of reproductive age who presents with signs of hemorrhagic shock. The list of differential diagnoses can be easily separated
into those associated with pregnancy and those that usually are not. Of course, a positive pregnancy test does not eliminate the possibility that the patient could have another process occurring in addition to pregnancy.

Functional ovarian cysts are common in reproductive-age women. Rupture or torsion of an ovarian cyst can cause lateral pelvic pain, mimicking EP. A ruptured, hemorrhagic corpus luteum cyst can occur with both IUP and EP. It may be extremely difficult to differentiate an EP from a ruptured corpus luteum of pregnancy because pain and bleeding can occur with both, as well as evidence of hemoperitoneum. Although pelvic sonography may be able to demonstrate an intrauterine gestation, the presence of a substantial hemoperitoneum may mandate surgical intervention (15).

Nonviable IUPs are readily confused with ectopic gestation. Vaginal bleeding with threatened, inevitable, or incomplete abortion is usually described as being much heavier than a menstrual period, and the pain is often reported to be midline, similar to menstrual cramps or labor. If the abortion is indeed inevitable or incomplete, the cervical os may be noticeably dilated, with extruding tissue or clot. A decidual cast may be shed in patients with an EP and may be confused with products of conception associated with an incomplete abortion. If possible, all tissue passed by the patient should be examined. While an experienced observer may be able to identify the presence of chorionic villi without microscopy, false-positive results have potential life-threatening consequences. The histological presence of chorionic villi obtained from the uterus/cervix, or passed vaginally by the patient virtually excludes the diagnosis of EP. The use of serial quantitative serum hCG titers and transvaginal sonography to distinguish viable IUP from nonviable IUP and EP is discussed below.

Pelvic pain and abnormal vaginal bleeding may also occur with salpingitis (PID). Usually, the pregnancy test will be negative, and fever and leukocytosis will be present. In rare cases, PID can occur in the presence of a very early pregnancy. Gastrointestinal disorders including appendicitis are also included in the differential diagnosis of EP.

Diagnostic modalities available in ambulatory settings can expedite the diagnosis of EP, minimizing this condition’s morbidity, mortality, and cost. The initial evaluation of any woman of reproductive age complaining of abdominal pain or abnormal vaginal bleeding should include a directed gynecologic history, a physical evaluation, and a sensitive and rapid urine pregnancy test. An algorithm for the evaluation and management of suspected EPs is presented in Fig. 3.2.