Pelvic Ultrasound

Excerpt

Ultrasound (US) is the key modality for the evaluation of contents of the female pelvis. It allows ready (and portable) imaging of the uterus, ovaries, and other structures at a reasonable cost and without ionizing radiation. Lack of irradiation is important since the ovary is particularly sensitive to radiation in young patients and those of reproductive age.

Pelvic US is performed either via the transabdominal (TA) or transvaginal (TV) approach. Gel is placed on the skin above the bladder allowing transducer contact without intervening air on the skin surface. A urine-filled bladder helps lift small bowel superiorly, out of the pelvis creating an optimal acoustic window and preventing bowel air from refracting or degrading the ultrasound beam. The US traverses the pelvis unimpeded through bladder fluid, insonating pelvic contents and returning to the transducer to be processed by the machine.

Images are obtained in the midline sagittal plane as well as parasagittal planes angled to the periphery of each hemipelvis. Similarly, transverse plane images are obtained by angling superiorly and inferiorly from a mid-bladder position. Real-time US allows the subtle angling of the transducer to obtain the best anatomic images even if the structures are not in perfect longitudinal or transverse plane alignment. The uterus is typically located in the midline, and the ovaries and adnexa are usually found lateral to the uterus. However, just like a uterus may not be midline, the position of the ovaries is somewhat variable, possibly in the low, mid, or upper pelvis. They may also be seen in the midline, superior to the uterus.