Pelvic Doppler Ultrasound
After dilation and curettage for a molar pregnancy with rising β‑hCG, the most appropriate next investigation is a pelvic Doppler ultrasound. 1
Rationale for Pelvic Doppler Ultrasound as First-Line Test
The European Society for Medical Oncology (ESMO) explicitly recommends pelvic Doppler ultrasound as the immediate first investigation when persistent or rising β‑hCG is confirmed after molar pregnancy evacuation 2, 1. This test serves multiple critical diagnostic and prognostic functions before any treatment decisions are made.
Key Diagnostic Contributions
Excludes a new intrauterine pregnancy, which is an absolute prerequisite before initiating chemotherapy—failure to confirm this could result in inadvertent termination of a viable gestation 1
Measures uterine size and volume to quantify disease burden within the pelvis 2, 1
Evaluates intra-pelvic spread of gestational trophoblastic neoplasia (GTN), informing anatomic staging decisions 1
Assesses vascularity using the Doppler pulsatility index, which functions as an independent prognostic factor for resistance to single-agent methotrexate therapy 2, 1
Subsequent Staging Algorithm
After the pelvic Doppler ultrasound is completed, proceed with the following sequence:
Chest X-ray is the second mandatory test because the lungs are the most common site of GTN metastasis 2, 1, 3
If chest X-ray is normal, no further imaging is required—CT chest can detect micrometastases in approximately 40% of patients, but these findings do not alter outcome or management in low-risk disease 2, 1
If chest X-ray shows lesions >1 cm, immediately proceed to MRI of the brain and CT of the chest/abdomen to rule out brain or liver metastases, which would significantly change therapeutic strategy and risk stratification 2, 1, 3
Definition of Rising β‑hCG Requiring Workup
Your patient meets criteria for persistent GTN if any of the following patterns are present 2, 1:
Two consecutive rises in β‑hCG of ≥10% over at least 2 weeks (days 1,7, and 14)
Four plateaued values over at least 3 weeks (days 1,7,14, and 21)
Persistence of detectable β‑hCG for ≥6 months post-evacuation
Critical Management Pitfalls to Avoid
Never start chemotherapy without ultrasound confirmation that no new pregnancy exists—this is the single most important reason to perform pelvic ultrasound first 1
Never perform re-biopsy of residual uterine tissue to confirm malignant transformation, as this carries a high risk of life-threatening hemorrhage 2, 1, 4
Do not order CT chest as the initial imaging study before obtaining a chest X-ray—micrometastatic disease detected only on CT does not influence management decisions in low-risk GTN 1
Additional Laboratory Tests
While pelvic Doppler ultrasound is the best next test, you should concurrently obtain 3:
Quantitative serum β‑hCG to establish a new baseline for treatment monitoring
Complete blood count with differential and platelet count
Comprehensive metabolic panel including liver and renal function tests before chemotherapy initiation
Thyroid function tests (TSH and free T4) if not recently checked, as hyperthyroidism can occur with markedly elevated β‑hCG 4
Risk Stratification After Staging
Once imaging is complete, apply the FIGO 2000 prognostic scoring system to determine whether single-agent methotrexate (score 0–6) or multi-agent EMA/CO chemotherapy (score ≥7) is required 2, 3, 5. The pulsatility index from the Doppler ultrasound contributes to predicting resistance to single-agent therapy 2, 1.