Ectopic pregnancy

This page works the case through in full, answer included. If you would rather reason it out yourself: Play this case

How the diagnosis is reached

Six weeks of amenorrhoea with a positive test, unilateral pain and spotting is an ectopic pregnancy until the pregnancy is located, and the point of the workup is that no single number settles it. A beta-hCG of 1,450 is not diagnostic on its own; what matters is the trajectory. A rise of only 15 per cent over 48 hours, against the roughly 35 per cent minimum a normal intrauterine pregnancy manages, says the trophoblast is not thriving, which fits an implantation somewhere it cannot sustain itself. The ultrasound then supplies the anatomy: an empty uterus at a hCG level where a sac should be visible, an adnexal mass, and free pelvic fluid. A thickened endometrial stripe without a sac is the decidual reaction, hormonal preparation of a uterus with nothing in it, and should not be mistaken for an early gestation. Treatment turns entirely on one question, which is whether she is stable, and she is. That permits intramuscular methotrexate, a dihydrofolate reductase inhibitor that halts the rapidly dividing trophoblast, followed by serial hCG until it falls to zero. Its candidacy conditions are the hCG below roughly 5000, an unruptured tube and no fetal cardiac activity. Rupture, instability or failed medical therapy mean laparoscopic salpingectomy or salpingostomy instead, and a suspected rupture goes straight to theatre rather than back to the scanner.

Key clinical clues

• Amenorrhea, positive pregnancy test, and unilateral pelvic pain
• Beta-hCG lower than expected for gestational age
• Abnormally slow rise in beta-hCG on repeat testing
• Empty uterus with adnexal mass and free fluid on transvaginal ultrasound
• Hemodynamic stability supports medical rather than surgical management

The case in full