Transvaginal ultrasound (TVUS)
- Transvaginal Ultrasound (TVUS) Overview
- 1st-line diagnostic imaging for female pelvic pathology (AUB, PMB, early pregnancy, pelvic pain, adnexal masses).
- High-frequency probe (5–10 MHz) -> High resolution, low depth of view.
- Requires an empty bladder (vs TAUS = full bladder).
- High-Yield Clinical Indications & Cutoffs
- Postmenopausal Bleeding (PMB):
- Endometrial thickness (EMT) ≤ 4 mm -> Reassurance / low risk of cancer. c
- EMT > 4 mm or ill-defined -> Endometrial Biopsy (EMB).
- Ectopic Pregnancy (EP):
- Discriminatory zone: β-hCG 1,500–2,000 mIU/mL + empty uterus -> Suspicion for EP.
- Findings: Adnexal ring sign, complex extraovarian mass, free pelvic fluid (hemoperitoneum).
- Early Pregnancy Loss Criteria:
- Crown-rump length (CRL) ≥ 7 mm w/ no fetal cardiac activity.
- Mean sac diameter ≥ 25 mm w/ no embryo.
- Ovarian Torsion:
- Findings: Enlarged, edematous ovary, “whirlpool sign” (twisted vascular pedicle), ↓ Doppler flow.
- Step 2 CK Trap: Normal Doppler blood flow does NOT rule out torsion (due to dual ovarian/uterine blood supply).
- Cervical Length (CL) Screening (16–24 wks):
- CL < 25 mm = short cervix.
- Prior spontaneous preterm birth (PTB) + short CL -> Vaginal progesterone + Cervical cerclage.
- No prior PTB + short CL -> Vaginal progesterone alone.
- Polycystic Ovary Syndrome (PCOS):
- “String of pearls” appearance (≥20 peripherally arranged follicles per ovary).
- Tubo-Ovarian Abscess (TOA):
- Multiloculated complex adnexal mass w/ thick walls and pelvic fluid/debris.
- Contraindications & Pitfalls
- Avoid in PPROM (risk of ascending infection; perform visual speculum exam instead).
- Avoid in active vaginal bleeding w/ unconfirmed placenta previa (perform TAUS first).
- Avoid in intact hymen / severe vaginismus -> Use TAUS or transrectal US.
- Inadequate for imaging large pelvic masses (>10 cm) extending above the pelvic brim -> Use TAUS/CT/MRI.