Diagnosis: Pregnancy of Unknown Location (PUL)
The correct diagnosis is D - Pregnancy of Unknown Location (PUL), which is defined as a positive pregnancy test (β-hCG 5000 mIU/mL) with no intrauterine or extrauterine gestational sac visible on ultrasound. 1
Why This is a Pregnancy of Unknown Location
This patient meets the precise definition of PUL: a positive pregnancy test without ultrasound visualization of either an intrauterine gestational sac or an adnexal mass suggestive of ectopic pregnancy. 1, 2 The β-hCG level of 5000 mIU/mL is well above the discriminatory threshold of 3000 mIU/mL, at which point a gestational sac should be definitively visible on transvaginal ultrasound if an intrauterine pregnancy exists. 3
Critical point: The abdominal ultrasound performed is inadequate for this evaluation. Transvaginal ultrasound is the gold standard and should have been performed, as it has 99% sensitivity for detecting ectopic pregnancy when β-hCG levels are elevated. 4, 5
Why the Other Options Are Incorrect
Missed miscarriage (A) is excluded because this diagnosis requires visualization of an intrauterine gestational sac with either a crown-rump length ≥7 mm without cardiac activity or a mean sac diameter ≥25 mm without an embryo. 3 No intrauterine pregnancy was visualized here.
Ovarian pregnancy (B) is excluded because this specific diagnosis requires ultrasound visualization of an extrauterine gestational sac with a yolk sac or fetal pole in the ovary. 1 No extrauterine pregnancy was identified on imaging.
Complete abortion (C) is excluded because this diagnosis requires documented passage of products of conception with declining β-hCG levels. 1 This patient has an elevated β-hCG of 5000 mIU/mL with acute symptoms, not a declining trend consistent with completed miscarriage.
Critical Management Algorithm for This Patient
Immediate next steps:
Perform transvaginal ultrasound immediately (not just abdominal), as this is mandatory for proper evaluation and has far superior sensitivity for detecting both intrauterine and ectopic pregnancy. 4, 5
Obtain serial β-hCG measurements every 48 hours to assess for appropriate rise (doubling in viable intrauterine pregnancy) or plateau/decline (suggesting ectopic or failing pregnancy). 1, 3
Assess clinical stability carefully - the left iliac fossa pain with nausea and vomiting raises concern for ectopic pregnancy, though the soft abdomen without peritoneal signs suggests hemodynamic stability. 4
Risk Stratification
This patient is at significant risk for ectopic pregnancy: Among patients with indeterminate ultrasound findings and β-hCG >2000 mIU/mL, approximately 57% have ectopic pregnancy. 1 With her β-hCG of 5000 mIU/mL and no visible intrauterine pregnancy, ectopic pregnancy is highly likely. 3
Studies show that 15% of patients with PUL ultimately have ectopic pregnancy, and approximately 7-20% of all PUL cases represent ectopic pregnancy. 1, 6
Common Pitfalls to Avoid
Never use β-hCG value alone to exclude ectopic pregnancy in patients with indeterminate ultrasound findings - this is a Level B recommendation from emergency medicine guidelines. 3, 4
Do not defer transvaginal ultrasound based on the abdominal ultrasound results, as transvaginal imaging is far more sensitive and may detect an ectopic pregnancy even at lower β-hCG levels. 4
Avoid premature diagnosis of nonviable pregnancy based solely on the absence of visible pregnancy at this β-hCG level - serial measurements and repeat imaging are essential. 3
Ensure immediate gynecology consultation or close outpatient follow-up given the high β-hCG level without visible intrauterine pregnancy, as this represents a high-risk PUL requiring specialist involvement. 3, 6