Ultrasound is the most common imaging modality used to diagnose gynecological problems. Also called sonography, ultrasound uses non-ionizing radiation in the form of sound waves and has no known harmful effects on the body. For this reason, it is considered safe for imaging the uterus and ovaries, which is known as pelvic ultrasound.
Transducers - Abdominal and Transvaginal Ultrasound
Transducers are special cameras that send sound waves into the body and listen for returning waves that bounce off of body structures. Two types of transducers are used for pelvic ultrasound. An abdominal transducer is placed on the skin on the front of the pelvis to obtain a larger view of the pelvic organs. It is best for viewing larger structures, but does not provide great detail. The transvaginal transducer is a long camera that is inserted into the vaginal canal. Transvaginal ultrasound is used to obtain more detailed images of the uterus and ovaries. It is best for imaging structures that are close to the camera.
Preparation
Ultrasound cannot be used to see through gas-filled bowel. For the abdominal portion of the ultrasound, the bladder is filled and used as a sonographic window, a structure that the sonographer, or ultrasound technician, looks through to find another organ. The bladder is the ideal sonographic window because it pushes bowel out of the way, and the fluid within the bladder enhances the transmission of sound waves to produce a clearer image.
It is necessary to follow specific instructions to ensure that the bladder will be full for the ultrasound. One should drink 32 ounces of water starting one hour before the exam and finishing 45 minutes prior to the exam. This gives the body 45 minutes to absorb the water and fill the bladder. After the abdominal ultrasound is completed, the bladder is emptied for the transvaginal portion of the exam.
Purpose of Pelvic Ultrasound
Pelvic ultrasound is used to diagnose many ailments. Ovarian cysts, fluid-filled sacs within the ovaries, are quite common. In a normal menstrual cycle, a cyst called a dominant follicle grows and releases an egg at the time of ovulation. If this cyst does not release an egg, it may continue to grow and cause pressure, mild discomfort, or a lot of pain.
Women at risk for ovarian cancer may undergo yearly pelvic ultrasounds. While ultrasound cannot distinguish between benign and cancerous masses, the results of the ultrasound may be used with other screening tests such as the CA 125 blood test to determine if further testing is necessary.
Fibroids are non-cancerous, muscular tumors within the uterus. They may cause spotting in between periods, heavy periods, long periods, and cramping. Women with uteruses that tip backwards may experience lower back pain. Depending on the size and location of the fibroids, they cannot always be seen with both transducers, so the abdominal and transvaginal transducers are both necessary for a complete examination.
Polyps may or may not be cancerous and can be found within the endometrium, the inner lining of the uterus. They may not always be seen with general pelvic ultrasound, and a hysterosonogram may be done. With hysterosonography, saline is injected into the endometrial canal and images are taken using the transvaginal transducer. Polyps appear as lumps surrounded by the saline.
Endometriosis is the growth of endometrial tissue outside of the uterus. It often attaches to bowel and cannot be identified with pelvic ultrasound. Sometimes, a mass of endometrial tissue may grow on an ovary and can be seen quite well. If endometriosis is suspected, a laparoscopy may be done. Laparoscopy is a surgical procedure that involves inserting a small camera into the pelvis.
The fallopian tubes cannot be seen using ultrasound unless they are filled with fluid, which may be the case with an ectopic pregnancy. An ectopic pregnancy occurs when the pregnancy is located outside of the uterus. It may not always be seen, so several follow-up ultrasounds may be necessary.
For more info:
RadiologyInfo: Ultrasound Imaging of the Pelvis
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