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Transvaginal Ultrasound Probe: How It Works, Uses and Reprocessing

A transvaginal (endocavity) probe puts the transducer a few centimetres from the uterus and ovaries, so it can use a higher frequency and show far more detail than a scan through the abdomen. It also touches mucous membrane, which makes cleaning and high-level disinfection part of every scan.

Also called Transvaginal probe, Endocavity probe, TVS probe

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What a transvaginal probe is

An endocavity probe has a small curved array at the tip of a long, slim handle. It is used transvaginally, and with the right cover also transrectally. Typical frequencies are about 4–9 MHz, and the array produces a wide fan-shaped field from the tip.

Tip array

A micro-convex array on the end of the shaft, often angled slightly, giving a wide sector close to the probe.

Handle and orientation mark

A ridge or light shows which side of the image corresponds to which side of the probe, which matters when you rotate between sagittal and coronal planes.

Biopsy guide

Many models accept a needle guide for procedures such as egg retrieval; check which guides fit the model on your quotation.

Why it shows more detail

Detail in ultrasound is limited mainly by frequency, and frequency is limited by depth. Placing the probe next to the pelvic organs shortens the sound path from perhaps 10 cm or more through the abdominal wall and full bladder to a few centimetres, so a higher frequency can be used.

Two panels: a transabdominal curvilinear probe imaging a deep uterus through a full bladder, and a transvaginal endocavity probe whose tip near the cervix gives a wide sector close to the uterus with only a small empty bladder in view.
Transabdominal scanning needs a full bladder as a window and gives the overview; transvaginal scanning needs an empty bladder and gives the detail. Many gynaecological and early pregnancy scans use both.
  • No full bladder is needed, and bowel gas is rarely in the way.
  • The trade-off is reach: the field of view ends a short distance from the tip, so large masses and the upper pelvis may need a transabdominal view.
  • Higher frequency also means higher sensitivity to probe position — small movements change the image a lot.

Read next Frequency, depth and resolution explained

What it is used for

UseWhat the scan looks for
Early pregnancyLocation of the pregnancy, the gestational sac, yolk sac, embryo and heartbeat, and crown–rump length for dating
Pregnancy of uncertain viabilityCriteria applied on transvaginal scans, such as an embryo with crown–rump length of 7 mm or more and no heartbeat, or a mean sac diameter of 25 mm or more with no embryo, which are diagnostic of pregnancy failure (SRU consensus, 2013)
GynaecologyEndometrial thickness and pattern, fibroids, ovarian cysts, adnexal masses, pelvic fluid
FertilityAntral follicle count, follicle tracking during stimulation, endometrium before transfer
OtherIUCD position, cervical length in pregnancy when indicated, pelvic pain

Read next Follicle tracking ultrasoundObstetric ultrasound machines

What is optimal: settings and technique

  • Ask the patient to empty her bladder first; a full bladder pushes the organs away from the probe.
  • Put gel inside the cover and on the outside of the cover; use sterile gel and a sterile cover where your protocol or a procedure requires it.
  • Use the highest frequency that reaches the area of interest, and reduce the depth so the uterus or ovary fills the screen.
  • Place the focal zone at the structure you are measuring.
  • Sweep systematically: sagittal from side to side, then rotate 90° to coronal and sweep from top to bottom.
  • Keep the thermal index low in early pregnancy and avoid routine pulsed Doppler before 11–14 weeks.
  • Offer a chaperone, explain each step, and record consent and who was present according to your clinic policy.

Read next MI and TI in early pregnancyRoom set-up, privacy and chaperones

Covers and high-level disinfection

Under the Spaulding classification, a transvaginal probe is a semi-critical device because it touches mucous membranes. The WFUMB Safety Committee advises a new cover for every patient and high-level disinfection between patients, because covers can leak: older studies reported leaks in 0.9–2% of condoms and 8–81% of commercial probe covers.

  • Remove and discard the cover.
  • Clean off gel and debris with running water or a damp cloth and mild non-abrasive soap, then dry.
  • High-level disinfect with a method the probe manufacturer approves for that model.
  • Disinfect the handle and the cable nearest the handle too, which also get touched.
  • Store the probe so it cannot be recontaminated, and fit a new cover for the next patient.
  • Keep a record of each disinfection cycle where your method allows it.
High-level disinfection methods described in the WFUMB guideline — always check the probe manufacturer’s compatibility list
MethodExample contact time in the guidelineNotes
Glutaraldehyde 2.4–3.2%20 minutes at 20 °CStrong odour; needs ventilation; largely replaced
Ortho-phthalaldehyde (OPA)5 minutes at 20 °CMilder odour, no activation needed
Chlorine dioxide wipe systemsSeconds per wipe stepThree-step pre-clean, disinfect and rinse wipes
Hydrogen peroxide 7.5%Per product instructionsBroad activity, including spores
Automated hydrogen peroxide mistPer device cycleClosed system that also treats the handle; needs the device

Read next Probe cleaning and disinfection for all probes

Buying a transvaginal probe

  • It must be compatible with your system platform and software version; probes are not interchangeable between brands.
  • Compare the frequency range and the field-of-view angle on the data sheet.
  • Check which needle guides fit, if you do procedures.
  • Ask for the manufacturer’s list of approved disinfectants and covers, and check it matches what your clinic uses.
  • Probe warranty terms, and how drops or cable damage are treated.
  • Diagnostic ultrasound systems and their transducers are medical devices. Under the Medical Device Act 2012 (Act 737), a medical device must be registered with the Medical Device Authority (MDA) before it is imported, exported or placed on the Malaysian market — ask for the registration number and check it on the MDA’s public register. Ultrasound uses sound, not ionising radiation, so unlike X-ray it does not need a licence under the Atomic Energy Licensing Act 1984.

Read next All probe types comparedProbe faults and repairs

Related guides

Obstetric and Gynaecology Ultrasound MachinesWhat an O&G clinic needs from an ultrasound machine — from early-pregnancy transvaginal scans to growth charts, Doppler and 4D.Ultrasound Probe Disinfection: Cleaning and High-Level DisinfectionWhich level of reprocessing each probe needs, the steps between patients, and why a probe cover alone is not enough for an endocavity scan.Fertility Ultrasound: Follicle Tracking and IVF ScanningFertility clinics run many short transvaginal scans and rely on consistent measurements to time treatment. What the equipment needs to do, from the baseline scan to egg collection.

Ultrasound Machine supply near you

Written quotes for clinics across Malaysia, handled from Batu Caves, Kota Kinabalu and Kuching.

See all 28 locations

Sources and further reading

  1. WFUMB Safety Committee — Guidelines for cleaning transvaginal ultrasound transducers between patients (Ultrasound Med Biol 2017)
  2. AIUM — Guidelines for cleaning and preparing external- and internal-use ultrasound transducers, 2025 revision
  3. Doubilet PM et al. Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med 2013
  4. ISUOG — Practice guidelines

Frequently asked questions

What frequency is a transvaginal ultrasound probe?
Typically about 4–9 MHz. The higher frequency than an abdominal probe is possible because the probe sits close to the uterus and ovaries.
Why is a transvaginal scan clearer than an abdominal scan?
The sound has a much shorter path, so a higher frequency can be used, which gives finer detail. No full bladder is needed and bowel gas is rarely in the way.
Does a transvaginal probe need high-level disinfection?
Yes. It is a semi-critical device that touches mucous membranes, and covers can leak, so the WFUMB guideline advises cleaning and high-level disinfection between every patient as well as a new cover.
Can the same probe be used transrectally?
Many endocavity probes are used for both, with an appropriate cover and the same cleaning and high-level disinfection between patients. Check the probe’s intended uses with the manufacturer.
Should the bladder be full for a transvaginal scan?
No. An empty bladder is better, because a full bladder pushes the pelvic organs away from the probe.
How often should a transvaginal probe cover be changed?
For every patient. A cover reduces contamination but does not replace cleaning and high-level disinfection, because covers can tear or leak; check the probe for gel or fluid under the cover each time it is removed.

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