Pelvic Ultrasonography

Pelvic US: Basics & Probes - Pelvic Peep Show

• Key approaches: Transabdominal (TAS) & Transvaginal (TVS).

• TAS: Uses lower frequency (3.5-5 MHz) curvilinear probe.
  • Provides wider field of view.
  • Requires full bladder as acoustic window.
  • Best for general pelvic overview, large masses.
• TVS: Uses higher frequency (5-9+ MHz) endocavitary probe.
  • Offers superior image resolution for details.
  • Requires empty bladder.
  • Optimal for uterus, endometrium, ovaries.

⭐ TVS provides superior detail for endometrial assessment and early pregnancy.

Normal Anatomy on US - Womb With A View

• Uterus: Pear-shaped. Position: Anteverted (common) or retroverted.
  • Myometrium: Homogeneous, mid-grey echotexture.
  • Endometrium: Appearance varies with menstrual cycle.
    • Proliferative: Trilaminar ("three-line sign"). Max thickness 4-8 mm.
    • Secretory: Thick, echogenic. Max thickness 7-16 mm.
    • Menstrual: Thin, echogenic line.
  • Cervix: Lower segment, more fibrous. Nabothian cysts (anechoic) common.
• Ovaries: Almond-shaped, hypoechoic stroma with peripheral anechoic follicles.
  • Location: Ovarian fossa, posterolateral to uterus.
  • Size: Variable, approx. 3 x 2 x 2 cm. Volume < 10 cc premenopausal.

  ⭐ Ovarian follicles are best visualized in the follicular phase; a dominant follicle can reach 18-25 mm before ovulation.

• Adnexa:
  • Fallopian tubes: Usually not visualized unless fluid-filled (e.g., hydrosalpinx).
• Pouch of Douglas (Cul-de-sac):
  • Posterior to uterus. Small anechoic free fluid can be normal (physiological).

Uterine Pathologies - Womb Worries Unveiled

• Leiomyomas (Fibroids): Most common benign uterine tumors.
  • USG: Well-defined, hypoechoic masses, often with posterior acoustic shadowing.
  • Types: Subserosal, Intramural (commonest), Submucosal (associated with abnormal uterine bleeding, infertility).
• Adenomyosis: Endometrial glands/stroma within myometrium.
  • USG: Diffusely enlarged, globular uterus; heterogeneous myometrium; myometrial cysts ("Swiss cheese" appearance); indistinct endometrial-myometrial junction; Venetian blind shadowing. Junctional zone > 12 mm.
• Endometrial Hyperplasia/Carcinoma:
  • USG: Thickened endometrium.
    • Postmenopausal: > 5 mm (if bleeding), > 11 mm (asymptomatic).
    • Premenopausal: Variable, > 15-20 mm often considered suspicious.
  • May show irregularity, heterogeneity, increased vascularity on Doppler. Tamoxifen effect: thickened, cystic endometrium.
• Asherman's Syndrome: Intrauterine adhesions.
  • USG: Thin or absent endometrial stripe, echogenic bands traversing uterine cavity. Hysterosonography is more diagnostic.

⭐ A thickened junctional zone (> 12 mm) on transvaginal ultrasound is a key diagnostic feature of adenomyosis, often described as a "bulky uterus with poor demarcation between endometrium and myometrium."

Ovarian & Adnexal Pathologies - Ovary Action & Alerts

• Common Cysts:
  • Follicular: Anechoic, <3 cm.
  • Corpus Luteum: "Ring of fire" (vascular).
  • Hemorrhagic: Lace-like/reticular, avascular.
  • Endometrioma: "Ground glass" echoes.
  • Dermoid: Hyperechoic (fat), Rokitansky nodule, "tip of iceberg".
• ⚠️ Ovarian Torsion: Surgical Emergency!
  • Enlarged ovary (>4 cm), stromal edema, peripheral follicles.
  • "Whirlpool sign" (twisted pedicle). Doppler: ↓/absent flow (variable, may be present).
• ⚠️ Ectopic Pregnancy: Life-threatening!
  • Empty uterus, adnexal mass (tubal ring), free fluid. β-hCG vital.
• PID / TOA: Hydrosalpinx ("cogwheel"), complex TOA.
• Malignancy Red Flags (US):
  • Solid irregular components, thick septa (>3 mm), papillary projections (≥4).
  • Ascites, ↑vascularity (low RI <0.4).
  • 📌 IOTA Simple Rules for risk.

⭐ Meigs' Syndrome: Benign ovarian tumor (fibroma) + ascites + pleural effusion.

High‑Yield Points - ⚡ Biggest Takeaways

• Transvaginal Sonography (TVS) provides superior resolution for uterus and adnexa over transabdominal USG.
• Endometrial thickness >5mm (postmenopausal bleeding) or >15mm (premenopausal, symptomatic) often warrants further investigation/biopsy.
• PCOS: Ultrasound shows "String of pearls" appearance, ovarian volume >10cc, and/or ≥12 antral follicles (2-9mm) per ovary.
• Uterine fibroids (leiomyomas): Typically hypoechoic, well-defined masses; sonographic appearance can vary, location is critical.
• Ovarian torsion: Key signs include an enlarged ovary, stromal edema, peripherally displaced follicles, and absent/reduced Doppler flow.
• Ectopic pregnancy: Suspect with an adnexal mass (often with "ring of fire" sign), an empty uterus, and possible free fluid in the pelvis, correlating with β-hCG levels.