Case: 22 year old G0 with a history of irregular menstrual intervals every 23-36 x 3-4 days has a difficult time determining when ovulation will occur with either the LH ovulation predictor kits or the LH ovulation monitor. She is trying to time an intrauterine insemination. The decision is made to proceed with serial ultrasonography to determine when a mature appearing egg can be triggered to ovulate with an injection of hCG.
Question: Would a transvaginal ultrasound or an abdominal ultrasound be more sensitive to determine subtle differences in ovarian follicular development?
Answer: The distance between the target (viewed) organ and the transducer (within the ultrasound probe) largely determines the (maximum) resolution of the ultrasound image. As the object being viewed gets closer to the transducer in the tip of the ultrasound probe the resolution of the image generally increases.
The transducer within the tip of the transvaginal probe can usually be placed within several centimeters of the ovaries and uterus. The abdominal ultrasound probes are much farther away, since the distance includes the entire thickness of the abdominal wall and the bowel that is located between the inside of the abdominal wall and the pelvic structures. Therefore, transvaginal ultrasonography has a major advantage over the abdominal approach when used for ovarian follicle studies (infertility work) or when evaluating an early intrauterine pregnancy.
Case: 28 year old G0 with a history of regular menstrual intervals every 28 x 3-4 days has an enlarged irregular firm uterus that is consistent with uterine fibroids (leiomyomas). An ultrasound is performed to assess the size of the fibroids as well as their relationship to the uterine (endometrial) cavity.
Question: When should the bladder be full and when should the bladder be empty for an (abdominal or transvaginal) ultrasound examination?
Answer: For transabdominal (“jelly on the belly”) ultrasonography a full urinary bladder is suggested to displace any bowel gas away from the abdominal wall that overlies the uterus and to provide a “window” (echo free region) for imaging the pelvic structures. A patient is often asked to drink several glasses of water (or flavored beverage) without voiding (urinating) since the bladder should ideally be full enough to extend over the fundus (top) of the uterus.
For transvaginal ultrasonography an empty urinary bladder is desirable, since a full bladder may displace the pelvic organs farther from the transducer, sound waves that must travel through a full urinary bladder may create an enhancement effect, a full bladder can compress and distort pelvic anatomy, and a full urinary bladder can be quite uncomfortable. A patient can void (urinate) immediately prior to the transvaginal ultrasound examination.
Case: 31 year old G0 with a history of irregular menstrual intervals every 2-4 months is surprised when she discovers that the ultrasound probe to be used for her examination of the ovaries and uterus is transvaginal.
Question: Does the transvaginal ultrasound probe hurt when inserted? How is the probe prepared (ultrasound gel and protective sheath) prior to insertion into the vaginal vault?
Answer: Many women believe that the “standard (ultrasound) approach” for examining pelvic organs is an abdominal ultrasound exam.
Transvaginal ultrasonography (TVS) has been used extensively in infertility practices over the past 10+ years since the transvaginal probes can provide an image with very high resolution.
The transvaginal probe that is used for TVS is generally no larger than a vaginal speculum (that is used to obtain pap smears) and should not hurt when inserted.
The transducer tip of the transvaginal ultrasound probe is covered with an ultrasound coupling gel and it is then covered with a protective rubber sheath or condom.
A small amount of coupling gel can be placed onto the outside of the protective sheath prior to placement into the vagina if desired. Generally no gel is applied when the TVS is used for infertility work since the gel can be spermatotoxic (toxic to sperm).
Case: 22 year old G1 P1 with a history of sudden severe left pelvic pain that has persisted for several hours undergoes a clinical evaluation that is to include a transvaginal ultrasound (TVS) exam.
Question: How is the TVS probe cleaned between patients to assure protection against cross infection?
Answer: The transvaginal ultrasound probe is placed within the vaginal canal during the ultrasound examination. Since the TVS probe is re-used from patient to patient the possibility of cross infection should be a major concern for the operator.
Disposable probe covers are generally used to cover the TVS probe during an examination. However, the probe should also be cleansed (disinfected) after each use. A variety of effective disinfectants are commercially available. The probe manufacturer should also provide information concerning effective disinfectants that can be used safely with the particular probe (since some disinfecting solutions may damage some probes).
The operator should also wear gloves during the examination and wash both hands thoroughly with soap and water after each examination to further reduce the risk of cross infection.
Case: 43 year old G0 with a history of heavy vaginal bleeding for 24 continuous days, previous regular menstrual intervals every 28-31 x 4-5 days, undergoing a clinical evaluation that is to include a transvaginal sonogram (TVS).
Question: Can the transvaginal ultrasound reliably assess the uterus (thickness of the uterine lining and presence of uterine fibroids = leiomyomata)?
Answer: The TVS is usually capable of providing a great deal of information about the uterus. In fact, the uterus is generally the most prominent landmark within the pelvis.
An enlarged uterus may be technically difficult to exam with TVS. In these situations, one should consider an abdominal ultrasound examination.
The endometrial lining of the uterine cavity is dynamic. The lining grows rapidly during the pre-ovulatory (follicular) phase of the menstrual cycle and is thickest during the post-ovulatory (luteal) phase of the menstrual cycle. In the follicular phase of the cycle, the endometrial lining tends to be 4-8 mm thick in anterior-posterior dimension. In the ovulatory phase of the cycle, the endometrial lining tends to be trilaminar (multilayered) and often measures 6-10 mm thick. In the luteal phase of the cycle, the lining is thickest, homogeneous rather than trilaminar and frequently measures 7-14 mm thick.
Fibroids (leiomyomata) within the wall of the uterus (transmural fibroids) or extending from the outer surface of the uterus (subserosal fibroids) can generally be identified and measured with TVS. Fibroids that predominantly extend into the uterine cavity (submucosal fibroids) are not reliably seen with TVS.
Case: 28 year old G0 is undergoing a transvaginal ultrasound (TVS) examination during a natural cycle to assess follicular development and is noted to have an apparent dominant follicle measuring 18 x 19 mm on the right ovary. The uterine lining is trilaminar (multilayered) and measures 8 mm thickness. The cervix has a hypoechoic interface along the endocervical canal with several simple cystic structures seen adjacent to this canal.
Question: Are the findings for the uterine cervix normal given the other information that is presented in this case?
The ultrasound findings are consistent with a woman in the peri-ovulatory phase of the menstrual cycle.
The lead (growing) ovarian follicle is usually thought to contain a mature egg once the average diameter reaches 16-18 mm.
The uterine endometrial lining usually measures up to 8mm thickness just prior to ovulation during a natural (non stimulated) cycle.
The cervical mucus increases to a maximal volume in the immediate preovulatory phase of the menstrual cycle, and is often seen as a linear echo free (hypoechoic) interface in the endocervical canal (since mucus has a high water content). Cystic structures along the cervical canal are often seen and probably represent Nabothian cysts (benign cysts of the small mucus secreting glands of the uterine cervix).
Case: 33 year old G1 P1 with a history of regular menstrual intervals every 28-29 x 4 days, a LMP starting 15 days ago, and left lower quadrant abdominal (pelvic) pain x 2-3 days. A pelvic ultrasound examination is performed during the clinical investigation (to assess this pain) that reveals the left ovary within the cul de sac behind the uterus (aka the pouch of Douglas), an irregular shaped 23 x 25 mm complex cystic structure in the left ovary, and a small amount (about 5 mL) of free fluid in the cul de sac (outlining the posterior wall of the uterus).
Question: Are the location and findings associated with the left ovary normal?
The ovaries are usually found adjacent to the uterus between the top (fundus) of the uterus and a set of major blood vessels within the lateral pelvic sidewall (the “iliac vessels”). Sometimes the ovaries are found behind the uterus in the pouch of Douglas. Rarely, the ovaries are not found in either of these locations and a hand is used to press down on the anterior abdominal wall over the side of the pelvis being examined to try to “push the ovary” into the pelvis.
Prior to ovulation, the ovaries often contain “follicles” (cysts containing eggs) that appear as echo free (solid black) translucent sharp bordered round ovarian cysts measuring up to 2-3 cm diameter. At ovulation, these cysts collapse as the egg and follicular fluid is released. Following ovulation, the progesterone producing corpus luteum cyst is formed and this appears as a complex fuzzy bordered cyst with internal echoes measuring up to 4-5 cm diameter.
A small amount of fluid (5-10 mL) is often found collected within the cul de sac behind the uterus. Complex structures identified within this fluid may be blood clots that may be associated with a ruptured ectopic pregnancy or a bleeding ovarian cyst. Free blood in the pelvis usually results in intense abdominal and pelvic pain. Free fluid without complex features may be follicular fluid from a ruptured ovarian cyst (around ovulation) or a normal finding.
Case: 61 year old postmenopausal woman with a history of dysfunctional uterine bleeding has an ultrasound to assess the pelvis during the clinical evaluation. Neither ovary is clearly identified on either abdominal or transvaginal ultrasonography.
Question: Are these findings associated with abnormal ovaries?
Answer: Not necessarily
During the reproductive years, the ovaries can usually be identified relatively easily because they contain follicles (cysts that contain eggs). These follicles are easy to see with ultrasonography so they can serve as “markers” for the ovary.
After menopause, the number of follicles that remain within the ovaries is very small or nonexistent. Therefore, the ovaries may be very difficult to identify in postmenopausal women. When color (Doppler) flow imaging is available the ovarian vessels can often be traced to an otherwise “invisible” ovary.
Case: 27 year old G0 with a history of a pelvic infection requiring intravenous antibiotics and a 3 day hospital stay has an ultrasound examination to assess the possibility of an abscess within the pelvis. The ultrasound revealed an unremarkable appearing pelvis (uterus, ovaries, cul de sac).
Question: Are the normal ultrasound findings consistent with an active pelvic infection?
The fallopian tubes are often difficult to impossible to assess with an ultrasound. Physical limitations of the ultrasound transducers that are currently available result in a relatively coarse outline of the pelvic structures, including the fallopian tubes. Additionally, the fallopian tubes do not normally contain free fluid so that there is no fluid – solid interface to provide a clear outline on ultrasonography. Most often, the fallopian tubes can be identified at their interface with the uterus and followed distally for a few centimeters before they are “lost from view.”
Inflammatory processes involving the fallopian tubes can produce enough edema (thickening of the wall) or localized free fluid to increase the visibility on ultrasonography. A hydrosalpinx or pyosalpinx (dilated fluid or pus filled fallopian tubes often with thickened walls) or a tubo ovarian complex (abscess) can occasionally be appreciated if the inflammatory process is severe.
The ultrasound appearance of the fallopian tubes during an acute episode of inflammation may be unremarkable since the changes associated with chronic inflammation have not yet taken place.
Case: 22 year old G1 P0 with a history of regular menstrual intervals every 28 x 3-4 days, status post appendectomy at 14 years of age, now about 2 weeks late for a flow. A urine pregnancy test is positive, the initial concentration of hCG at 5 weeks 4 days by dates is lower than expected (540 IU/L) and the hCG titer has not been increasing normally (620 IU/L two days later when the concentration would be expected to be at least 66% greater than the initial value). An ultrasound is performed to assess the possibility of an ectopic pregnancy and an unremarkable pelvis is reported (normal uterus, ovaries and fallopian tubes).
Question: Does this ultrasound examination rule out the possibility of an ectopic pregnancy?
Transvaginal ultrasonography is a valuable diagnostic tool that can assess the location of an early pregnancy about 1-2 weeks prior to abdominal ultrasonography. The presence of embryologic structures associated with a normal pregnancy can also often be identified.
An intrauterine pregnancy can initially be reliably seen via identification of a gestational sac at an hCG concentration of about 2,000 IU/L (local variability for this discriminatory zone exists). If an intrauterine pregnancy is identified then the chance of an ectopic pregnancy is small (twins with one pregnancy in the uterus and one pregnancy in the tube have been reported but are not common).
If the hCG titer were lower than 1,000 IU/L then it would be uncommon to identify a gestational sac in the uterus. Therefore, in this case the finding of a normal appearing uterus is not unexpected.
The history of previous abdominal surgery and an abnormally rising hCG titer increase the risk of an ectopic pregnancy. The classic ultrasound appearance of an ectopic pregnancy is an empty uterus (no gestational sac in the cavity), an adnexal mass (a cystic structure in the region of the ovary and fallopian tube that is distinct from the ovary), and fluid in the cul de sac behind the uterus. This classic appearance is uncommon to find in the presence of an early unruptured ectopic pregnancy.
An early ectopic pregnancy may result in no specific clinical symptoms. Therefore, maintaining a high suspicion of an ectopic pregnancy is very important.
Case: 25 year old G1 P0 at 8 weeks gestational age with a history of intermittent vaginal spotting to light flow since 5 weeks gestational age, an ultrasound examination at 6 weeks gestational age that revealed a viable SIUP (single intrauterine pregnancy with active heart beat) with a 2 x 2 cm retroplacental collection of fluid (subchorionic hematoma). A repeat ultrasound is scheduled to assess embryonic growth and viability as well as resolution versus progression of the fluid between the placenta and the uterine lining.
Question: Is the ultrasound examination able to predict whether this woman will have a miscarriage (spontaneous pregnancy loss)? Is there any harm to the pregnancy of multiple ultrasound examinations during early pregnancy?
Answer: The transvaginal ultrasound examination of an early pregnancy is able to collect a great deal of information that is clinically useful.
Identification of a gestational sac within the uterine cavity should be reassuring for the physician and the pregnant patient. Except on the rare occasions when a heterotopic pregnancy (twins with one pregnancy in the uterus and another in an ectopic location) exists the presence of an intrauterine pregnancy rules out an ectopic pregnancy.
High resolution transvaginal ultrasound examinations are increasingly able to assess embryologic development (sonoembryology). Reportedly, at 5 weeks gestation (21 days after fertilization) the embryo is about 1.5 mm long and the fetal heart begins to pulsate. At 6 weeks gestation the embryo is about 4 mm long and the fetal heartbeat can often be seen clearly with a transvaginal ultrasound.
Placental cells (with an inner cytotrophoblast layer and an outer syncytiotrophoblast layer) rapidly grow around the gestational sac to produce a second echogenic rim (double line, double ring, double contour) that can distinguish the gestational sac from other types of fluid that might collect in the uterine cavity during early pregnancy.
Sonoembryology is often not able to reliably predict an impending spontaneous pregnancy loss. Absence of a fetal heart beat after the heart was identified at beating earlier in the pregnancy defines a fetal demise (death) or nonviable pregnancy.
A subchorionic collection of blood is associated with a partial disruption in the integrity of the connection between the placenta and the uterine lining. If the retroplacental collection is observed to be located between the pregnancy and the internal os (opening) of the cervix then this generally has a more favorable prognosis. If the collection is observed to be located between the placenta and the uterine lining at the top (fundus) of the uterus then this often has a less favorable prognosis.
If the embryo has good interval growth and a persistent fetal heartbeat, then the pregnancy has enough placental exchange of nutrients and waste products with the uterus to allow for growth. Sometimes continued development occurs despite the coexistence of a large subchorionic hematoma.
Ultrasound examinations of early pregnancy are not known to cause any birth defects. Sonoembryology has been widely used for many years and is generally considered to be safe for the pregnancy.