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ULTRASOUND
PelvisDemonstration data

Pelvic Ultrasound

Pelvic ultrasound is the primary imaging modality for evaluating the female reproductive organs and adnexa. Combining transabdominal and transvaginal approaches, it assesses the uterus, endometrium, ovaries, and pelvic cul-de-sac. It is central to the workup of pelvic pain, abnormal uterine bleeding, and suspected gynecologic masses, and guides risk stratification of adnexal lesions.

Indications

  • Pelvic or lower abdominal pain, suspected adnexal torsion or tubo-ovarian abscess
  • Abnormal uterine bleeding, menorrhagia, or postmenopausal bleeding
  • Evaluation of fibroids, adenomyosis, or an enlarged uterus
  • Characterization of ovarian or adnexal masses and cysts
  • Endometrial assessment including thickness and polyps
  • Localization of an intrauterine device or retained products of conception
  • Evaluation of infertility and follicular monitoring
  • Assessment of congenital uterine anomalies

Contraindications & Cautions

  • No absolute contraindications; no ionizing radiation, safe in all patients
  • Transvaginal approach is generally avoided in patients who are not sexually active or decline it; use transabdominal or transperineal alternatives
  • Obtain consent and offer a chaperone for the transvaginal examination
  • Active menstruation may limit endometrial assessment and transvaginal scanning
  • Full bladder required for transabdominal imaging can cause patient discomfort
  • Follow ALARA for Doppler exposure

Patient Preparation

  • Transabdominal: fill the bladder by drinking 500-1000 mL of water and not voiding to create an acoustic window
  • Transvaginal: empty the bladder immediately before the examination
  • Explain both approaches and obtain verbal consent for the transvaginal scan; offer a chaperone
  • Document last menstrual period and menopausal status, which affect interpretation of endometrial thickness
  • Supine positioning for transabdominal; lithotomy or elevated pelvis for transvaginal
  • Use a fresh probe cover and appropriate disinfection for the transvaginal transducer

Technique & Parameters

  • Transabdominal: curvilinear 3.5-5 MHz probe in sagittal and transverse planes through a full bladder
  • Transvaginal: high-frequency 5-9 MHz endocavitary probe for detailed pelvic assessment
  • Uterus measured in three dimensions with assessment of position, myometrium, and serosa
  • Endometrium measured as the maximal double-layer anteroposterior thickness in the sagittal plane
  • Ovaries identified adjacent to the internal iliac vessels and measured in three planes; volume calculated
  • Color and spectral Doppler to assess ovarian and adnexal vascularity and, when torsion is suspected, arterial and venous flow
  • Saline infusion sonohysterography may be added to evaluate the endometrial cavity for polyps or submucosal fibroids
  • Evaluate the posterior cul-de-sac for free fluid

Systematic Review

  • Uterus: size, position (ante- or retroverted), contour, myometrial echotexture
  • Endometrium: thickness, echogenicity, focal lesions, fluid in the cavity
  • Cervix: length and any mass or nabothian cysts
  • Right and left ovaries: size, volume, follicles, cysts, solid components
  • Adnexa: masses, hydrosalpinx, ectopic pregnancy signs
  • Cul-de-sac: free fluid, loculated collections
  • Bladder and distal ureters as visualized
  • Doppler flow to ovaries and any adnexal mass

Key Findings & Significance

  • Hypoechoic well-defined myometrial masses causing uterine enlargement indicate leiomyomas
  • Heterogeneous myometrium with cysts and an indistinct endomyometrial junction suggests adenomyosis
  • Thickened endometrium in a postmenopausal woman (>4-5 mm with bleeding) warrants sampling
  • A simple anechoic ovarian cyst with thin walls and posterior enhancement is benign
  • Complex adnexal mass with solid components, thick septa, and vascularity raises concern for malignancy
  • Absent ovarian venous or arterial flow with an enlarged edematous ovary suggests torsion
  • Free pelvic fluid may be physiologic or indicate hemorrhage, infection, or ruptured cyst

Differential Considerations

  • Enlarged uterus: fibroids, adenomyosis, malignancy, pregnancy
  • Thickened endometrium: hyperplasia, polyp, carcinoma, retained products, tamoxifen effect
  • Simple cystic adnexal mass: functional cyst, cystadenoma, paraovarian cyst, hydrosalpinx
  • Complex adnexal mass: hemorrhagic cyst, endometrioma, dermoid, tubo-ovarian abscess, ovarian neoplasm
  • Solid adnexal mass: fibroma, pedunculated fibroid, ovarian malignancy, metastasis
  • Acute pelvic pain: torsion, ruptured cyst, ectopic pregnancy, pelvic inflammatory disease

Pearls & Pitfalls

  • Correlate endometrial thickness with menopausal status and phase of the cycle to avoid over- or under-calling pathology
  • A hemorrhagic cyst can mimic a solid mass; internal lace-like reticular strands and lack of internal Doppler flow are reassuring
  • Torsion can occur with preserved arterial flow; whirlpool sign and an enlarged ovary are more reliable
  • Endometriomas show homogeneous low-level internal echoes (ground-glass); watch for decidualization in pregnancy
  • Apply the O-RADS ultrasound risk stratification system to standardize adnexal mass reporting
  • Always attempt to visualize both ovaries; a nonvisualized ovary should be stated
  • Do not mistake a pedunculated subserosal fibroid for an adnexal mass; trace the vascular bridge

Structured Report

  • State the approach used (transabdominal and/or transvaginal) and technical adequacy
  • Report uterine measurements, position, and myometrial findings including fibroids with location and size
  • Report endometrial thickness and appearance, correlated to menopausal status
  • Describe each ovary with measurements and any cysts or masses using O-RADS descriptors and score
  • Note free fluid and any additional pelvic findings
  • Impression: summarize significant findings with an O-RADS score for adnexal lesions and recommend follow-up, MRI, or gynecologic referral as appropriate

References

  • ACR O-RADS Ultrasound Risk Stratification and Management System
  • ACR-AIUM-SRU Practice Parameter for the Performance of Ultrasound of the Female Pelvis
  • Society of Radiologists in Ultrasound consensus on management of asymptomatic ovarian and adnexal cysts
  • IOTA (International Ovarian Tumor Analysis) group ultrasound criteria

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.