What is pelvic ultrasound imaging?
Ultrasound is high-frequency sound that is generated electronically by a machine and special crystals in a probe. The sound travels through your body, and bounces off different tissues and back to a receiver on the same probe. These sound waves are interpreted into a digital image. Ultrasound is not the same as X-ray, and does not make use of ionising radiation. A pelvic ultrasound provides pictures of the structures and organs in the lower belly or pelvis.
What is it used for?
There are three types of pelvic ultrasound:
- abdominal (transabdominal)
- vaginal (transvaginal or endovaginal) for women
- rectal (transrectal) for men
A Doppler ultrasound exam may be part of a pelvic ultrasound examination.
In women, a pelvic scan is most often performed to evaluate the pelvic organs like the bladder, ovaries, uterus, cervix or fallopian tubes, and is often required when symptoms include pelvic pain, abnormal bleeding, and other menstrual problems. It can also identify palpable masses such as ovarian cysts uterine fibroids. In men, this examination is often focused on the bladder and prostate, including the seminal vesicles.
A transvaginal ultrasound is usually performed to view the uterus including the lining and the wall and its thickness. Other structures visualised include the ovaries, cervix and bladder. The transrectal ultrasound is a special study of the prostate gland.
How should I prepare?
Wear comfortable, loose-fitting clothing and remove all clothing and jewellery in the area to be examined. You may be asked to wear a gown. Sometimes you will be asked to make sure that your bladder is full, as this can help to make visualisation of the organs better.
How is the procedure performed?
As you lie on the examination table, the radiologist or sonographer will spread warm gel on your skin and press the transducer firmly against your body, moving it back and forth over the area of interest until the desired images are captured. Sometimes it is slightly uncomfortable as the radiologist or sonographer passes over an area that is tender, but this is transient. They will regularly stop to take measurements. Most ultrasound examinations are painless, fast and easy.
Transabdominal pelvic ultrasound: you will be asked to lie on your back. The area to be scanned will be exposed: this includes your lower abdomen, down to the area just above your pubic bone.
Transvaginal: This i s very much like a gynecological exam and involves the insertion of the probe (or transducer) into the vagina after you have emptied your bladder. Only the tip of the transducer is placed into the vagina, and this is smaller than the standard speculum used when performing a Pap test. The probe is covered with a protective clear plastic and lubricated with a small amount of gel. It is usually performed with the patient lying on her back, possibly with her feet in stirrups similar to a gynecologic exam.
Transrectal: For a transrectal ultrasound, a protective cover is placed over the transducer; it is lubricated, and then placed into the rectum. The patient usually lies on his or her side, facing away from the examiner, with the knees and hips slightly bent.
When the examination is complete, the patient may be asked to dress and wait while the ultrasound images are reviewed. However, the sonographer or radiologist is often able to review the ultrasound images in real time, as they are acquired, and the patient can be released immediately.
These ultrasound examinations are usually completed within 30 minutes.
What are the risks?
Yes, even in pregnancy, there are no harmful effects.
What are the limitations?
Ultrasound waves are reflected by air or gas; therefore ultrasound is not an ideal imaging technique for the bowel. Intestinal gas may also prevent visualisation of deeper structures such as the pancreas and aorta. Patients who are obese are more difficult to image because tissue attenuates (weakens) the sound waves as they pass deeper into the body.