Transvaginal Pelvic Ultrasound

Transvaginal ultrasound provides high-resolution imaging of the uterus, endometrium and ovaries and is the primary modality for evaluating abnormal bleeding, pelvic pain, adnexal masses and early pregnancy. The endocavitary probe is placed close to the pelvic organs, giving superior spatial resolution compared with the transabdominal approach, which remains useful as a survey for large masses beyond the field of view.

Indications

Abnormal uterine bleeding and assessment of endometrial thickness
Acute or chronic pelvic pain and suspected ovarian torsion
Suspected ectopic pregnancy or pregnancy of unknown location with correlation to serum hCG
Characterisation of an adnexal or ovarian mass
Early pregnancy dating and viability assessment
Infertility work-up and follicular monitoring

Contraindications & Cautions

Virginal patients or those declining the endocavitary approach; use transabdominal/transperineal alternatives
Not appropriate after certain gynaecological surgery or where vaginal access is precluded
Requires patient consent and a chaperone per local policy
Active heavy bleeding may limit assessment though it is not an absolute contraindication

Patient Preparation

Empty the bladder immediately before the transvaginal examination
A full bladder is preferred for the preceding transabdominal survey
Obtain informed consent and provide a chaperone
Use a single-use probe cover with sterile gel and follow high-level probe disinfection between patients
Record last menstrual period and relevant hCG level

Technique & Parameters

Endocavitary transducer 5-9 MHz with disposable cover and coupling gel
Systematic sagittal and coronal/transverse sweeps of the uterus, cervix and both adnexa
Measure endometrial thickness in the midline sagittal plane as the double-layer maximum, excluding fluid
Assess ovaries for volume, follicle number and any lesion; measure in three orthogonal planes
Colour and spectral Doppler to assess ovarian and adnexal vascularity and, when relevant, arterial/venous flow in torsion
Correlate any intrauterine or extrauterine gestation with the discriminatory hCG level

Systematic Review

Uterus: position, size, myometrial echotexture, fibroids or adenomyosis
Endometrium: thickness, echogenicity, focal lesions and intracavitary fluid
Ovaries: volume, follicles, corpus luteum and any solid or cystic lesion
Adnexa: masses, hydrosalpinx and tenderness on probe pressure
Cul-de-sac and pelvis: free fluid or complex/echogenic fluid suggesting haemorrhage
In pregnancy: location and number of gestational sacs, yolk sac, embryo and cardiac activity

Key Findings & Significance

Intrauterine gestational sac with yolk sac confirms intrauterine pregnancy; embryo with cardiac activity confirms viability (typically by ~6 weeks / CRL >7 mm)
Empty uterus with hCG above the discriminatory level (~1500-2000 mIU/mL) and an adnexal mass or tubal ring suggests ectopic
Thickened endometrium in a postmenopausal bleeder (>4-5 mm) warrants sampling
Complex or solid adnexal mass with vascularity raises concern for neoplasm (apply O-RADS)
Ovarian enlargement with absent or reduced venous/arterial flow and whirlpool of the pedicle suggests torsion
Echogenic free fluid in the cul-de-sac suggests haemoperitoneum in the setting of ectopic

Differential Considerations

Pregnancy of unknown location: early intrauterine pregnancy vs ectopic vs failed/completed miscarriage
Adnexal mass: functional cyst, endometrioma, dermoid, cystadenoma/cystadenocarcinoma, tubo-ovarian abscess
Thickened endometrium: proliferative change, polyp, hyperplasia, carcinoma, retained products
Acute pelvic pain: torsion, ruptured cyst, ectopic, PID, appendicitis
Enlarged uterus: fibroids, adenomyosis, gestation, malignancy

Pearls & Pitfalls

Correlate all early-pregnancy findings with quantitative hCG and prior scans before diagnosing failure or ectopic
The double-decidual sac and intradecidual signs help distinguish a true gestational sac from a pseudosac of ectopic
Normal Doppler flow does not exclude ovarian torsion; use grey-scale morphology and the twisted pedicle
Apply O-RADS ultrasound risk stratification to standardise reporting of adnexal lesions
Measure the endometrium excluding intracavitary fluid and any hypoechoic inner myometrium

Structured Report

State approach (transvaginal +/- transabdominal), bladder status and probe frequency
Report uterine dimensions and endometrial thickness/pattern with the measurement plane
Describe both ovaries (volume, follicles, lesions) and any adnexal mass using O-RADS descriptors
Note free fluid and its character; in pregnancy give location, dating and viability
Give an impression addressing the clinical question and recommend follow-up, hCG correlation or MRI as appropriate

References

AIUM-ACR-ACOG-SMFM-SRU Practice Parameter for the Performance of Detailed Diagnostic Obstetric Ultrasound
ACR O-RADS US Risk Stratification and Management System (Andreotti RF et al., Radiology 2020)
AIUM Practice Parameter for the Performance of an Ultrasound of the Female Pelvis
Doubilet PM et al. Diagnostic Criteria for Nonviable Pregnancy Early in the First Trimester. NEJM 2013

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

Transvaginal Pelvic Ultrasound

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References