Transvaginal Ultrasound: What It Is Used For and How to Prepare
Transvaginal Ultrasound: What It Is Used For, How to Prepare and Differences with Transabdominal Ultrasound
Everything you need to know about endovaginal ultrasound: indications, preparation, procedure and when the gynecologist prefers it over abdominal ultrasound.
Reviewed by diagnostic imaging specialists · GSMED Imaging ColombiaThe transvaginal ultrasound —also called endovaginal ultrasound or transvaginal sonography— is an imaging study that uses a specialized high-frequency probe inserted into the vagina to obtain detailed images of the uterus, ovaries, fallopian tubes and nearby pelvic structures.
Unlike transabdominal ultrasound, the probe is placed directly next to the organs being studied, allowing for higher-resolution images, especially during the first weeks of pregnancy and in the diagnosis of gynecological conditions. In Colombia, it is one of the most requested complementary studies in gynecology and obstetrics.
What is transvaginal ultrasound and what is it used for?
Transvaginal ultrasound uses a long, thin probe (endovaginal transducer) that is inserted into the vagina with a disposable cover and lubricating gel. Because it is so close to the pelvic organs, it can use higher ultrasound frequencies (5–12 MHz) than the abdominal probe, resulting in clearer, more detailed images.
The study allows the gynecologist or radiologist to evaluate:
Size, shape, endometrium, fibroids and polyps
Follicles, cysts, tumors and polycystic ovary syndrome
When they are dilated or an ectopic pregnancy is suspected
Gestational sac, embryo and cardiac activity from week 5–6
Cervical length in the risk of preterm birth
Transvaginal vs Transabdominal: key differences
Both techniques are complementary. The gynecologist decides which one to use —or combine them— depending on the clinical indication and the patient's characteristics.
| Feature | Transvaginal | Transabdominal |
|---|---|---|
| Image resolution | ⬆ High (5–12 MHz) | ⬇ Moderate (2–5 MHz) |
| Full bladder required | No — empty bladder | Yes — full bladder |
| First trimester (≤12 weeks) | Best option | Limited |
| 2nd and 3rd trimester | Complementary | Best option |
| Patients with obesity | Superior | Poorer quality |
| Gynecological pelvic evaluation | Gold standard | Initial approach |
Gynecological and obstetric indications
🩺 Gynecological indications
- →Abnormal uterine bleeding — endometrial evaluation and possible polyps or submucosal fibroids
- →Chronic or acute pelvic pain — ovarian cysts, endometriosis, ovarian torsion
- →Infertility and ovarian stimulation — antral follicle count, dominant follicle monitoring
- →Polycystic ovary syndrome (PCOS) — microcyst count and ovarian volume
- →Uterine fibroids — location, size and impact on the endometrial cavity
- →Postmenopausal evaluation — endometrial thickness as a marker of pathology
🤰 Obstetric indications
- →Confirmation of intrauterine pregnancy — visualization of the gestational sac from week 4+
- →Suspected ectopic pregnancy — absence of intrauterine sac with positive beta-hCG
- →Threatened miscarriage — evaluation of embryonic cardiac activity in the first trimester
- →Precise dating of pregnancy — crown-rump length (CRL) measurement between weeks 6–12
- →Cervical length — evaluation of the risk of preterm birth in the second trimester
How to prepare for a transvaginal ultrasound
Preparation is simple and different from that for a transabdominal ultrasound:
Urinate just before the exam. A full bladder is not only unnecessary, but it can displace the uterus and make visualization difficult.
The study is pelvic, not abdominal. You can eat and drink normally before the exam.
If the doctor indicated a specific indication (follicle follow-up, cervical measurement), bring the order with that information.
For endometrial studies, some doctors prefer to perform them in the first half of the cycle (days 5–10). Ask your doctor if there is a specific day indicated.
💡 Important: Active menstruation is not a contraindication for the exam. The patient may decline the study if she wishes; in that case, the doctor will evaluate alternatives such as transabdominal or transrectal ultrasound. The technique requires the patient's informed consent.
How the procedure is performed
The patient lies in the gynecological position (supine with knees flexed). The examiner places a disposable cover (protective condom) over the probe and applies sterile lubricant gel or water to facilitate insertion.
The probe is gently inserted into the vagina. The depth of insertion is minimal—usually just a few centimeters—to achieve the best acoustic window. The patient may feel slight pressure, but the procedure should not be painful.
The sonographer gently rotates and angles the probe to obtain views of the uterus (body, fundus, cervix), both ovaries, and the Douglas space. The uterus, endometrial thickness, and ovaries are measured.
In cases of suspected ovarian torsion, ectopic pregnancy, or endometrial flow assessment, color Doppler is added to evaluate vascularization.
The exam takes between 10 and 20 minutes. At the end, the doctor describes the findings in a report with measurements and representative images. In many centers, the results are delivered the same day.
Common findings on transvaginal ultrasound
🔵 Functional ovarian cyst
Very common in reproductive age. They are usually simple cysts (follicles or corpus luteum) that disappear spontaneously within 1–3 cycles. They are monitored by ultrasound.
🔴 Uterine fibroid (leiomyoma)
Benign tumor of the uterine muscle. Transvaginal ultrasound allows them to be classified (submucosal, intramural, subserous) and their impact on the endometrial cavity to be measured.
🟡 Endometrial polyp
Focal thickening of the endometrium, frequently a cause of intermenstrual bleeding. Hysterosonography (with saline) improves its detection.
🟣 Ovarian endometrioma
Cyst with homogeneously echogenic content ("ground glass"). Highly suggestive of ovarian endometriosis. Requires clinical correlation and specialized follow-up.
🟢 PCOS (Polycystic Ovary Syndrome)
≥20 follicles of 2–9 mm or ovarian volume >10 ml in one or both ovaries. It is integrated with clinical findings and hormonal parameters for diagnosis according to the Rotterdam criteria.
⚠️ Ectopic pregnancy
Adnexal mass with or without cardiac activity, absence of an intrauterine sac with positive beta-hCG. It is a medical emergency that requires immediate diagnosis.
Frequently Asked Questions
The most common questions about transvaginal ultrasound.
Does your institution need gynecological ultrasound equipment?
At GSMED Imaging, we distribute ultrasound machines with high-resolution endovaginal probes for gynecology, fertility, and obstetrics clinics in Colombia.
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