Your question contains several parts.
How is the process of the transvaginal ultrasound different than just
a regular ultrasound? I imagine it's inserted into the vagina? Is it
What you call a "regular" ultrasound is known in medical practice as an transabdominal ultrasound. It is a very common procedure, which, depending on the countries, may be done by physicians, nurses or radiology assistants. A transvaginal ultrasound consists of an ultrasound probe inserted (after ultrasound gel is applied on it) into the vaginal cavity. Patients undergoing this procedure describe it as non painful. It is the same sensation as when a speculum is inserted in the vagina to do a pap smear.
Would a regular ultrasound ordered by an OBGYN be able to
detect/differentiate typical benign ovarian cysts from an ovarian
tumor? Are there images that can show the different appearance of an ovarian cyst from an ovarian tumor?
Adnexal masses can be classified as:
- Benign ovarian (polycystic ovaries, teratomas, functional cysts,...)
- Benign non-ovarian (paratubal cyst, hydrosalpinges,...)
- Primary malignant ovarian (carcinoma,...)
- Secondary malignant ovarian (ie metastasis)
The International Ovarian Tumor Analysis (IOTA) group has described 6 essential patterns which help differentiating benign masses (ie for example ovarian cysts in PCOS) or malignant masses using an ultrasound:
- Is the cyst unilocular, multilocular, unilocular solid,...?
- How is the cystic content? Is it anechoic, haemorrhagic, mixed,...?
- Any wall irregularities?
- How is the vascularisation?
- Are there any shadows behind the lesions?
- Is there liquid in the peritoneal cavity (=ascites)?
Using these criteria might help differentiating benign masses with malignant masses. Here some examples:
Additionally, the IOTA group has even described some features and rules which should orient towards a benign or malignant cause:
If doubt persist, some indications in the personal history or other clinical examination (+/- biomarkers) might help providing additional evidence in favor of a benign or malignant cause. Finally, confirmation can only be done through histology.
Though, the IOTA rules are good performers in predicting the malignancy risk of ovarian masses as suggested by this large systematic review:
Kaijser et al. Presurgical diagnosis of adnexal tumours using mathematical models and scoring systems: a systematic review and meta-analysis. Hum. Reprod. Update (May/June 2014) 20 (3): 449-462.
Is a transvaginal ultrasound needed in that case?
The IOTA rules are based on transvaginal ultrasound.
Here also a summary of the recommendations from the Royal College of Obstetricians and Gynaecologists regarding management of suspected ovarian masses in premenopausal women:
A pelvic ultrasound is the single most effective way of evaluating an
ovarian mass with transvaginal ultrasonography being preferable due to
its increased sensitivity over transabdominal ultrasound.
Additional information can be found here regarding ultrasound features of ovarian masses (open access):
- for the images and features description: https://www.bmus.org/static/uploads/resources/IOTA_Simple_Rules_-_Susanne_Johnson.pdf