How to diagnose an ectopic pregnancy in a 7-week pregnant woman with vaginal bleeding, severe pelvic cramping, and decreasing quantitative human chorionic gonadotropin (hCG) levels, where transvaginal ultrasonography (US) is unable to locate the pregnancy?

From the Guidelines

To definitively diagnose an ectopic pregnancy in this case, the patient should undergo laparoscopic surgery, which is the gold standard for diagnosis when clinical presentation and imaging are inconclusive. With symptoms of vaginal bleeding, worsening severe pelvic cramping, dropping hCG levels, and inability to locate the pregnancy on transvaginal ultrasound, there is a high suspicion for ectopic pregnancy. Before surgery, additional diagnostic steps include serial quantitative hCG measurements (typically 48 hours apart) to confirm the abnormal pattern, and possibly a dilation and curettage (D&C) to rule out intrauterine pregnancy by examining tissue samples. If no chorionic villi are found in the uterine samples and hCG levels don't decline appropriately after D&C, this strongly suggests ectopic pregnancy. In some cases, empiric methotrexate treatment (50 mg/m² intramuscularly) might be considered if the patient is hemodynamically stable with no signs of rupture, hCG levels are relatively low (typically <5000 mIU/mL), and there's strong clinical suspicion 1. However, surgical confirmation remains necessary in uncertain cases to prevent delayed diagnosis of a potentially life-threatening condition, as ruptured ectopic pregnancy can cause severe internal bleeding and shock.

The use of ultrasound, particularly transvaginal ultrasound, is crucial in the evaluation of patients with suspected ectopic pregnancy, as it can help identify the location of the pregnancy and guide further management 1. The discriminatory threshold, which is the level of hCG above which an intrauterine pregnancy should be visible on ultrasound, is an important concept in the diagnosis of ectopic pregnancy. However, this threshold can vary depending on the ultrasound criteria used and the institution, and it is not always a reliable indicator of ectopic pregnancy 1.

In patients with an indeterminate ultrasound, the risk of ectopic pregnancy can be difficult to predict, and further evaluation and management are necessary to prevent delayed diagnosis and potential complications 1. The use of serial hCG measurements and possibly D&C can help confirm the diagnosis and guide further management. Laparoscopic surgery remains the gold standard for diagnosis and treatment of ectopic pregnancy, especially in cases where the diagnosis is uncertain or the patient is unstable 1.

Key points to consider in the diagnosis and management of suspected ectopic pregnancy include:

• High suspicion for ectopic pregnancy based on clinical presentation and imaging findings
• Use of serial hCG measurements and possibly D&C to confirm the diagnosis
• Consideration of empiric methotrexate treatment in stable patients with low hCG levels and strong clinical suspicion
• Laparoscopic surgery as the gold standard for diagnosis and treatment in uncertain or unstable cases
• Importance of prompt diagnosis and treatment to prevent delayed diagnosis and potential complications, such as severe internal bleeding and shock 1.

From the Research

Diagnosis of Ectopic Pregnancy

To definitely diagnose an ectopic pregnancy, the following steps can be taken:

• A high level of clinical suspicion is required for any pregnant patient who presents with vaginal bleeding and/or pelvic pain 2
• Workup should begin with immediate triage based on vital signs, a pregnancy test, and transvaginal ultrasound 2
• The definitive diagnosis of ectopic pregnancy can be made with ultrasound visualization of a yolk sac and/or embryo in the adnexa 3
• However, most ectopic pregnancies do not reach this stage, and patient symptoms combined with serial ultrasonography and trends in beta human chorionic gonadotropin levels are used to make the diagnosis 3
• Pregnancy of unknown location refers to a transient state in which a pregnancy test is positive but ultrasonography shows neither intrauterine nor ectopic pregnancy, and serial beta human chorionic gonadotropin levels, serial ultrasonography, and, at times, uterine aspiration can be used to arrive at a definitive diagnosis 3

Diagnostic Modalities

The following diagnostic modalities can be used to diagnose ectopic pregnancy:

• Transvaginal ultrasound scan to identify the location of the pregnancy 4
• Quantitative beta hCG (discriminatory zone) 5
• Other pregnancy hormone (progesterone) testing 5
• Invasive procedures (laparoscopy, culdocentesis, D & C) 5
• Observation (serial beta hCG) 5

Clinical Presentation

Ectopic pregnancy can present with the following symptoms and signs:

• Pelvic or abdominal pain 4
• Amenorrhoea, missed period or abnormal period 4
• Vaginal bleeding 4
• Pelvic, abdominal, adnexal or cervical motion tenderness 4
• Rebound tenderness and abdominal distension 4