Female pelvic ultrasound
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Pelvic ultrasound is usually the initial modality for imaging gynecologic pathology, including acute pelvic pain and chronic pelvic pain. The exam normally involves two components: a transabdominal (TA) evaluation and a transvaginal (TV) / endovaginal (EV) evaluation.
Normal ultrasound anatomy
consists of endometrium, junctional zone, and myometrium
the appearance of the endometrium depends on which part of a woman's menstrual cycle she is in, and can vary from 2-15 mm
the endometrium normally has a three-layer appearance at midcycle but is usually more homogeneous later
the junctional zone may be difficult to detect on ultrasound
the uterus is normally tilted toward the anterior abdominal wall (anteverted)
if the uterus is enlarged, the transabdominal exam may be needed to evaluate the full size
the ovaries also vary in size with the menstrual cycle
due to varying sizes of follicles
nulliparous: maximum volume of 9 mL
parous: maximum volume of 15 mL
a dominant follicle in the ovaries reaches 20-25 mm diameter at maturity
do not call an anechoic ovarian structure a "cyst" in a premenopausal woman unless it is >30 mm
the dominant follicle becomes the corpus luteum
fallopian tubes are not normally seen on ultrasound unless dilated or surrounded by free pelvic fluid
Pelvic ultrasound usually includes two components:
transabdominal (TA) evaluation
transvaginal (TV) evaluation
some prefer the term "endovaginal" (EV)
The transabdominal component is always performed first. The transvaginal component is performed second and, because of the higher resolution of the transvaginal probe, is usually very helpful for an evaluation of the pelvic structures.
Despite the usefulness of the transvaginal exam, it may not be performed if:
the patient does not want it
the patient has never had sexual intercourse (virgo intacta)
A mid-low frequency transducer (e.g. up to 5 MHz) is usually used. A full bladder is used as an acoustic window to achieve better imaging of the uterus and adnexa.
The transabdominal exam is used for a general overview of the pelvis and may be necessary in some situations in order to image the entirety of some pelvic pathologies.
A mid-high frequency probe (e.g. >7 MHz) is usually used. The bladder is emptied before the exam. The higher frequency allows a better spatial resolution and Doppler evaluation of the pelvis.
mural nodularity can be missed in large cystic lesions, make sure to carefully evaluate the entire wall
if there is trouble determining which organ a mass is arising from, a bimanual technique can be used in which the mass is imaged while the two organs are manually pushed in different directions
if the mass moves with an organ, it arises from the organ
if the mass slides past an organ, it arises from the adjacent organ
if the uterus is retroverted, consider endometriosis