Ultrasound examination, as an imaging diagnostic technique, offers advantages such as ease of operation, high visual clarity, non-invasiveness, and the ability to perform repeated scans. However, ultrasound images can be complex, and there is significant variation in the skill and experience of examiners, leading to a misdiagnosis rate as high as 9.1%.Intrauterine Findings: Absence of gestational sac, embryonic bud, or primitive fetal heartbeat. However, pseudocystic sacs occur in approximately 20% of cases. These result from endometrial decidualization and minor intrauterine blood retention during pregnancy. Typically, they exhibit indistinct contours, incomplete stratification, irregular margins, and fail to enlarge with gestational age—sometimes even diminishing. Careful observation allows differentiation.Characteristics of adnexal masses and/or uterovesical fluid: Adnexal masses are typically composed of gestational sacs, hematomas, and surrounding adherent intestinal loops.
1. Prior to tubal pregnancy rupture, an irregularly shaped, poorly defined hypoechoic area is visible paracervically. As the gestational sac develops, a round or oval dark zone representing the sac becomes visible within the hypoechoic area. In rare cases, the embryonic bud and primitive fetal heartbeat may even be discernible within the sac, providing definitive evidence for ectopic pregnancy diagnosis.Reports indicate the former is observed in 20% of cases, while fetal heartbeat is detected in 12%.
2. During tubal pregnancy abortion, blood flows from the fimbrial end of the fallopian tube. A small amount of free fluid appears as an anechoic or hypoechoic area within the paracolic mass and the uterovesical pouch.
3. In early stages of tubal pregnancy rupture, the gestational sac escapes through the ruptured fallopian tube. Due to bleeding, a hyperechoic mass with disorganized internal echo distribution and increased echogenicity is visible in the parametrium. The gestational sac is embedded within the hematoma. In extremely rare cases, the echogenicity of the gestational sac may be visible, and even the embryonic bud and primitive fetal heartbeat may be observed.
If the rupture has occurred for an extended period, repeated bleeding at the rupture site forms an enlarged paracervical mass with chaotic internal echoes, variable reflection intensity, and thickened margins—clinically recognized as a chronic ectopic pregnancy. In interstitial tubal pregnancies, before the fertilized egg penetrates the muscle layer, the gestational sac may be seen enclosed within the thickened muscle layer. Its sonographic appearance resembles that of a cornual pregnancy, making differentiation between the two challenging.
II. Measurement of Chorionic Gonadotropin
Technologies for measuring chorionic gonadotropin (hCG) have significantly advanced over the past decade. The hCG β-subunit radioimmunoassay accurately detects early pregnancy and serves as a reliable method for diagnosing ectopic pregnancy.
The syncytiotrophoblast cells in the villi secrete chorionic gonadotropin. Due to the extremely thin mucosa and muscle layer of the fallopian tube, which cannot supply the necessary nutrients to the villous cells, ectopic pregnancies exhibit lower β-hCG concentrations in plasma. The β-hCG radioimmunoassay can detect the presence of a fertilized egg as early as the ninth day.In normal early pregnancy, β-hCG levels double every 1.2 to 2.2 days. However, in 86.6% of ectopic pregnancies, the doubling time is slower, and the absolute β-hCG values are also lower than in normal pregnancies.
III. Posterior Fornix Aspiration
This is currently a widely used method for diagnosing ectopic pregnancy. Aspiration of purulent or serous fluid excludes tubal pregnancy. However, the absence of aspirated fluid does not rule out tubal pregnancy.