Gynecologists generally choose from four ultrasound tools when assessing the pelvis. However, only two of those options — transabdominal and transvaginal ultrasound — are well known and frequently used. The remaining two, translabial and transrectal ultrasound, are less prevalent but often viable alternatives to a transvaginal exam for imaging the lower pelvis.
When contraindications for a transvaginal ultrasound are present, transrectal ultrasonography can help to fill the gap and provide valuable imaging information for diagnosis and treatment.
What Is Transrectal Sonography?
The transrectal sonographic exam is just what it sounds like: a transvaginal or other long, narrow transducer is used to image the pelvis from a rectal approach through the anal sphincter. The transducer is covered with both a protective sheath and lubricating jelly.
The scanning technique is quite similar to that of the transvaginal ultrasound examination - they both have very similar vantage points and scanning planes. It is important to note that the transrectal approach can still make use of color and power Doppler and 3D ultrasound techniques to provide more information on findings.
Transrectal sonography has been found to provide clinically useful images of diagnostic quality whose resolution is as good as or better than images obtained via transabdominal imaging. One study published in the Journal of Menopausal Medicine found that transrectal and transvaginal ultrasound are equally effective when assessing polycystic ovarian syndrome (PCOS).
When Transrectal Should Be Considered
The transrectal ultrasound can be used to complement a transabdominal ultrasound exam when a transvaginal approach is not possible. Transvaginal exams are extremely useful for contributing additional information to a pelvic assessment; often, without this information, the patient will be unable to receive a diagnosis and may need further imaging with a pelvic MRI.
Transrectal ultrasonography should be considered in situations including:
- Patients who have never engaged in penetrative sexual intercourse
- Agenesis of the vagina
- Premature rupture of membranes
- Postmenopausal patients who are unable to tolerate a vaginal approach
- Patients who have undergone recent cervical or vaginal procedures
As with a transvaginal ultrasound, the transrectal ultrasound exam can add information about pelvic pathologies such as deep infiltrating endometriosis, endometrial polyps or ovarian concerns such as masses or cysts.
Care should be taken to counsel the patients on this option. Explain the procedure, outline what to expect and answer any questions or concerns. It may help to remind the patient that a transrectal ultrasound should not be painful, and to show them the relatively small size of the probe used.
A Safe Alternative for Providing Necessary Care
Transrectal ultrasonography is an examination that has been proven to be safe and beneficial in situations where a transvaginal ultrasound is needed but not possible. This technique is an alternative to consider to complement and enhance the pelvic ultrasound exam.
