Transvaginal ultrasound gives resolution that transabdominal scanning simply cannot match — the probe sits centimetres from the pelvic organs and runs at much higher frequency. It is also the most intimate examination most sonographers perform, and doing it well is as much about how you conduct the encounter as how you angle the probe.

New graduates are often more anxious about this study than any other. That anxiety is reasonable and it fades quickly with a clear routine.

Before You Start

Consent

Explain what the examination involves, why it is being performed, and that the patient can stop at any point. Obtain and document verbal consent. Follow your department's policy — some require written consent.

A patient can decline. Transvaginal imaging is not mandatory. If a patient declines, perform the best transabdominal study you can, document that transvaginal imaging was declined, and note the resulting limitations. Do not pressure.

Chaperones

Offer a chaperone to every patient, regardless of the sonographer's gender. Document the offer, whether it was accepted, and the chaperone's name. Many departments require a chaperone for all transvaginal examinations — know your local policy, and follow it even when the patient says it is unnecessary.

Bladder

The bladder should be empty, which is the opposite of transabdominal pelvic imaging. A full bladder pushes the uterus out of the field and away from the probe. Ask the patient to void immediately before the study.

Safeguarding and Special Situations

Consider whether transvaginal is appropriate at all in patients who have never been sexually active — a transrectal or transabdominal approach may be preferable, and this should be discussed sensitively.
Be alert to signs of distress and to disclosures. Know your department's safeguarding pathway.
For patients with a history of sexual trauma, offering additional control — such as letting the patient insert the probe herself — can make the difference between a completed study and an abandoned one.

Probe Preparation

This is an infection control matter and there is no room for shortcuts.

High-level disinfection between every patient. Endocavity probes require high-level disinfection, not a wipe-down. Follow the manufacturer's instructions and your department's validated process.
Single-use cover. Apply gel inside the cover to couple with the probe face, then a sterile lubricant outside.
Check the cover for defects before and after use. If a cover fails during the examination, the probe requires full reprocessing and the incident should be documented.
Latex allergy — confirm before selecting a cover, and use a latex-free option where indicated.

Use sterile lubricant, not ultrasound gel, on the outside of the cover.

Orientation

This is what confuses people most at the start.

The transvaginal probe images in two planes, and they are not the same as transabdominal planes:

Sagittal (long axis): Marker toward the ceiling with the patient supine. The image shows the uterus in long axis. The bladder appears at the top left of the screen, the uterine fundus to the right or left depending on flexion.
Coronal (transverse): Rotate the probe 90° counterclockwise from sagittal. This gives a coronal plane through the pelvis — the plane in which the uterine cavity and both cornua are best appreciated.

The mental adjustment: you steer by moving the probe handle in the opposite direction to where you want the beam to go. Pushing the handle down angles the beam up toward the anterior structures. This feels backwards for about a week and then becomes automatic.

Depth and frequency: Start with a depth of around 8–10 cm and reduce once you find the uterus. Endocavity probes run at 5–9 MHz or higher — use the highest frequency that still reaches the structure of interest.

A Systematic Sweep

Doing the same sequence every time is what stops you missing things.

1. Uterus — sagittal. Enter and find the uterus. Establish version and flexion. Sweep fully from the right lateral to left lateral border so no part of the myometrium is unexamined. Measure length and AP.

2. Endometrium. In true midsagittal, measure double-layer thickness at the thickest point. Assess the endometrial–myometrial junction. Look for focal lesions and intracavitary fluid.

3. Uterus — coronal. Rotate 90°. Measure transverse diameter. This is the best plane for assessing the cavity shape and detecting congenital uterine anomalies — a bicornuate or septate uterus is often invisible in sagittal and obvious in coronal.

4. Cervix. Withdraw the probe slightly. Assess the cervical canal, look for nabothian cysts, and measure cervical length if indicated.

5. Right adnexa. Angle the probe toward the right pelvic sidewall. The internal iliac vessels are the key landmark — the ovary usually sits just anterior and medial to them. Measure the ovary in three planes and calculate volume. Assess follicles and any lesion.

6. Left adnexa. Same approach.

7. Pouch of Douglas. Return to midline and angle posteriorly. Assess for free fluid, quantify it, and characterize it as simple or complex.

Finding a Difficult Ovary

Ovaries are the most common thing to lose, and there are reliable ways to find them.

Use the internal iliac vessels as the landmark. Find them with colour Doppler and the ovary is usually immediately adjacent.
Apply gentle abdominal pressure with your free hand. This brings a high ovary down into range and is the single most effective manoeuvre. Explain what you are doing first.
Look outside the expected location. Post-hysterectomy ovaries, and ovaries displaced by fibroids or adhesions, can sit high or laterally.
Follow the ovarian ligament from the uterine cornu.
Postmenopausal ovaries are small, atrophic, and follicle-free, which makes them genuinely hard to see. Failure to visualize a postmenopausal ovary after a careful search is common and should be reported as such — it is not the same as reporting a normal ovary.

Doppler Considerations

Colour and spectral Doppler are valuable in the adnexa — assessing lesion vascularity, and evaluating ovarian arterial and venous flow where torsion is suspected.

On torsion: the presence of flow does not exclude ovarian torsion. Dual blood supply and intermittent torsion both mean a torsed ovary can retain demonstrable flow. Grey-scale findings — an enlarged, oedematous ovary with peripherally displaced follicles — carry more weight, and clinical suspicion outranks Doppler.

Keep output low. Apply ALARA principles. Use the minimum power and dwell time needed, particularly in early pregnancy.

During the Examination

Narrate what you are doing without over-explaining. "I'm going to look at the left ovary now, you may feel some pressure."
Watch for discomfort. Localized tenderness under the probe is a genuine clinical sign worth documenting — sonographic tenderness over an adnexal mass or in the pouch of Douglas is meaningful information.
Stop if the patient asks you to. Document what was and was not completed.
Keep the examination efficient. A confident, systematic study is more comfortable for the patient than a prolonged uncertain one.

Key Images to Capture

Uterus sagittal — with length and AP measurements
Endometrium — double-layer thickness in true midsagittal
Uterus coronal — transverse measurement and cavity assessment
Cervix
Right ovary — two planes, three measurements, volume
Left ovary — two planes, three measurements, volume
Both adnexa with colour Doppler
Pouch of Douglas
Any focal lesion — two planes, measurements, Doppler
Documentation of consent and chaperone

When Transvaginal Is Not the Right Answer

Large masses extending above the pelvic brim will be incompletely assessed — combine with transabdominal imaging.
Patient declines, or the examination is inappropriate — document and adapt.
Some pelvic pathology sits too high for the transvaginal field of view entirely.

The best pelvic studies frequently use both approaches. Transabdominal gives the overview and catches what sits above the pelvis; transvaginal gives the detail.

SonoBuddy keeps pelvic protocols, ovarian volume calculations, and endometrial thresholds available offline.

Transvaginal Ultrasound: Technique, Orientation, and Patient Care