Ectopic pregnancy until proven otherwise … even with a negative serum hCG test: A case report

Ectopic pregnancy is commonly considered in the differential diagnosis for first-trimester vaginal bleeding and acute abdominal pain in women of reproductive age. Negative human chorionic gonadotropin (hCG) tests have been considered the gold standard to rule out this life-threatening diagnosis and appropriately rising hCG levels are thought to exclude it as well. In the unique case reported here, pathology confirmed ectopic pregnancy is identified in the setting of a negative serum hCG test. The patient was a 23-year-old woman (with one living child and one earlier miscarriage) who presented to the emergency department (ED) with sudden onset of abdominal pain, vaginal bleeding and syncope. She was tachycardic but normotensive and had both a negative serum hCG test and a negative urine hCG test. Imaging demonstrated a hemoperitoneum and right adnexal mass. She was taken for emergency exploratory surgery. The right fallopian tube had a tubal mass consistent with an ectopic pregnancy as well as 500 mL of blood. Pathology confirmed the ectopic pregnancy. A literature review revealed only two prior documented cases of pathology-confirmed ectopic pregnancy in the setting of a negative serum hCG test. The patient had experienced an abortion two months earlier without a documented intrauterine pregnancy. Her hCG levels were followed to <5 mIU/mL and she had not yet had return of menses at the time of her presentation. Perhaps a chronic ectopic could explain this unusual case. This case highlights that an ectopic pregnancy should never be excluded from the differential diagnosis in a woman of reproductive age.