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.

Pelvic Ultrasound

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References