Several algorithms have been proposed to identiY ectopic pregnancy. Most include these key components: physical indings, transvaginal sonography (TVS), serum 3-hCG level measurement-both the initial and the subsequent pattern of rise or decline, and diagnostic surgery, which includes dilation and curettage (D&C), laparoscopy, and occasionally, laparotomy (Fig. 19-3). Algorithm use applies only to hemodynamically stable women, and those with presumed rupture undergo prompt surgical therapy. For a suspected unruptured ectopic pregnancy, all diagnostic strategies involve trade-ofs. Strategies that maximize detection of ectopic pregnancy may result in termination of a normal intrauterine pregnancy (IUP). Conversely, those that reduce the potential for normal pregnancy interruption will delay ectopic pregnancy diagnosis. Patient desires for the index pregnancy are also discussed and may inluence these trade-ofs.
apid and accurate determination of pregnancy is essential to iden tiY an ectopic pregnancy. Current pregnancy tests use enzyme linked immunosorbent ssays (ELISAs) for the beta subunit of hCG. With these assays, lower limits of detection are 20 to 25 mIU/mL for urine and :;5 mIU/mL for serum (Greene, 2015).
With bleeding or pain and a positive pregnancy test result, an initial TVS is typically performed to identiY gestation loca tion. If a yolk sac, embryo, or fetus is identiied within the uterus or the adnexa, then a diagnosis can be made. In many cases, however, TVS is nondiagnostic, and tubal pregnancy is still a possibility. In these cases in which neither intrauterine nor extrauterine pregnancy is identiied, the term pregnancy of unknown location (PUL) is used until additional clinical infor mation allows determination of pregnancy location.
Levels above the Discriminatory Zone. Several investigators ure to visualize a uterine pregnancy indicates that the pregnancy either is not alive or is ectopic (Barnhart, 1994). Some institu tions set their discriminatory threshold at ::1500 mIU/mL, whereas others use ::2000 mIU/mL. Connolly and associates (2013) suggested an even higher threshold. hey noted that with live uterine pregnancies, a gestational sac was seen 99 percent of the time with a discriminatory level of >3510 mIU/mL.
If the initial 3-hCG level exceeds the set discriminatory level and no evidence for an IUP is seen with TVS, then ectopic pregnancy is a concern. The diagnosis is narrowed in most cases to a failing IUP, a recent complete abortion, or an ectopic pregnancy. Early multifetal gestation also remains a possibility. Without clear evidence for ectopic pregnancy, serial 3-hCG level assessment is reasonable, and a level is checked 48 hours later. This averts unnecessary methotrexate administration and avoids harming an early normal multifetal pregnancy. With greater concern for an ectopic gestation, D&C is another option to distinguish an ectopic from a failing IUP. Importantly, patient factors greatly influence these decisions.
Levels below the Discriminatoy Zone. If the initial 3-hCG level is below the set discriminatory value, pregnancy location is often not technically discernible with TVS. With these PULs, serial 3-hCG level assays are done to identiY patterns that indicate either a growing or failing IUP. Levels that rise or fall outside these expected parameters increase the concern for ectopic pregnancy. hus, appropriately selected women with a possible ectopic pregnancy, but whose initial 3-hCG level is below the discriminatory threshold, are seen 2 days later for further evaluation. Trends in levels aid diagnosis.