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A transvaginal ultrasound is an internal scan that uses high-frequency sound waves, too high for the human ear, to build a live picture of your pelvic organs. A slim probe, about the width of a tampon, is placed a short way into the vagina, which brings it close to the uterus, ovaries, cervix and surrounding tissue, so the images are clearer and more detailed than a scan done over the belly.1 It uses sound, not ionising radiation, so there is no radiation dose and it is considered very safe.1 It usually takes about 15 to 20 minutes, and most people feel pressure rather than pain.3
What a transvaginal ultrasound can show
A sonographer carries out the scan and captures the images, and a radiologist then interprets them.1 The view takes in the ovaries, fallopian tubes, bladder, uterus, cervix, upper vagina, and the muscles and ligaments of the pelvis.1
Doctors use transvaginal ultrasound to look into a wide range of questions, including endometriosis, adenomyosis, cancers, tumours and other masses, fibroids, ectopic and uterine pregnancy, ovarian cysts, fistulas, bowel problems, and other anomalies.1 In pregnancy it can also help tell a harmless enlarged ovary, such as in hyperreactio luteinalis, apart from a tumour.1
Often a scan over the abdomen is done first, then the transvaginal scan is added for a closer look.1
What a normal scan can and cannot rule out
A transvaginal ultrasound is very good at picking up structural things, such as an ovarian cyst, a fibroid, or an endometrioma, which is a cyst of endometriosis sitting on the ovary.2 It is less reliable for superficial or deeply hidden endometriosis, where even a skilled scan can look normal.2
So a clear scan is reassuring, but it is not the whole story. If your symptoms point to endometriosis and the scan comes back normal, that alone does not rule it out, and it is worth staying on the case with a practitioner who knows the condition well.2
What to expect during the scan
You will usually undress from the waist down and lie back on the couch with your knees bent.3 The sonographer covers the probe with a smooth protective sheath and lubricating gel, then gently guides it a little way into the vagina.3 You may be offered the choice to insert the probe yourself.3
During the scan the sonographer moves the probe slightly to see different structures. You might feel some pressure, similar to putting in a tampon, but it should not be sharp or painful.3 Tell whoever is scanning you if anything hurts, as they can stop or adjust at any point.
How to prepare
There is very little to do beforehand, and you can eat and drink as normal.3 Your clinic will tell you whether they want your bladder full or empty, because that changes how your organs sit and show up on the screen.3
If you have your period you can still have the scan; you will just need to take out a tampon first.3 Wear clothes that are easy to slip out of.
After the scan
There is no recovery time, so you can go straight back to your day.3 A little gel may leak for a short while, and some people notice very light spotting for a day or so if the tissue was a bit sensitive; both settle on their own.3 Your results usually come back through the doctor who referred you.
When a transvaginal ultrasound will not be used
It is not always the right scan. It is generally avoided after recent vaginal surgery, where there is a vaginal obstruction, if a pregnant patient has ruptured membranes or bleeding from placenta praevia, and where there is an imperforate hymen.1 A child cannot have one without parental consent.1 In these situations a scan over the abdomen, or a different test, is used instead.
Your consent, your call
An internal scan only goes ahead with your consent, and you can withdraw that consent at any time.1 You are allowed to ask questions before you agree, to have a chaperone or a support person in the room, to insert the probe yourself, or to ask whether a scan over the abdomen could answer the question instead.
None of this makes you a difficult patient. It is your body and your appointment, and a good clinic will expect you to have a say.
Frequently asked questions
Does a transvaginal ultrasound hurt?
For most people it is uncomfortable rather than painful, more a feeling of pressure or fullness, much like inserting a tampon.3 If you have a condition that makes the area tender, such as vaginismus or vulval pain, tell the sonographer beforehand so they can go slowly, and remember you can stop at any time.
Can I have a transvaginal ultrasound on my period?
Yes. You can have the scan during your period, and you will just be asked to remove a tampon first.3 Sometimes a scan is deliberately timed to a particular point in your cycle, so follow any timing your clinic gives you.
Does a normal scan mean I do not have endometriosis?
Not necessarily. Ultrasound reliably finds ovarian endometriomas and other structural changes, but it can miss superficial or deep endometriosis, so a normal scan does not rule it out.2 If your symptoms continue, keep working with a practitioner who takes endometriosis seriously.
This article is general information and not a substitute for personalised medical advice. If you are worried about your symptoms, or you are due a scan and feeling anxious about it, please talk to your doctor, sonographer or an experienced practitioner.
References
- Nahlawi S, Gari N. Sonography transvaginal assessment, protocols, and interpretation. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; updated 2022 Sep 16. https://www.ncbi.nlm.nih.gov/books/NBK572084/
- Nisenblat V, Bossuyt PMM, Farquhar C, Johnson N, Hull ML. Imaging modalities for the non-invasive diagnosis of endometriosis. Cochrane Database Syst Rev. 2016;2(2):CD009591. https://pubmed.ncbi.nlm.nih.gov/26919512/
- Cancer Research UK. Transvaginal ultrasound scan. https://www.cancerresearchuk.org/about-cancer/tests-and-scans/transvaginal-ultrasound-scan
