Because of its small probe and high frequency, vaginal ultrasound can be performed in the vagina as a circular rotation scan, close to the pelvic organs, showing well the internal microstructure of the organs, independent of the thickness of the abdominal wall, the degree of bladder filling, and the interference of intestinal gas, it has become a routine way of obstetrical and gynecological ultrasound examination.
Vaginal ultrasound is available to all sexually active women, especially those with hypertrophy of the abdominal wall, patients with acute abdomen and those with unfilled bladders. Vaginal ultrasound can be used to monitor follicular development and to evaluate the endometrium and to predict the timing of ovulation to detect abnormal follicular development. Depending on the length of the menstrual cycle, monitoring is started on the fifth to seventh day of menstruation, once every other day, and once daily until ovulation after the follicle reaches 10 mm in diameter. After ovulation, monitoring will be done every other day until the onset of menstruation.
For women with regular menstruation who are simply monitoring ovulation, monitoring can be started from the 8th to 12th day of menstruation. At this time, the follicles in the ovaries increase in size day by day and appear to have clear borders with increased tension, forming a dominant follicle with a diameter of about 10mm 6 to 7 days before ovulation. The endometrium is thickening day by day with hypoechogenicity, and the edges of the uterine cavity are strongly echogenic, forming a “three-line sign”.
On the 13th to 14th day of menstruation, the ovarian volume and the dominant follicle on the ovulatory side increased day by day, reaching a maximum value until the day before ovulation.
The endometrial thickness increases to its maximum value of about 12-13 mm on the day before ovulation.
Ovulation is a short transient process that is difficult to observe with ultrasound, but some signs suggest ovulation.
1. disappearance of the dominant follicle.
2. significant shrinkage or wrinkling of the dominant follicle by more than 5 mm, collapse of the inner wall and scattered fine dotted echogenicity seen inside.
3. In 40% to 50% of women, a small amount of fluid accumulation sonogram is seen in the rectal trap of the uterus within 1-2 days after ovulation. The thickness and sonogram of the endometrium during ovulation are the same as the day before ovulation.
During follicle monitoring, in addition to normal ovulation, abnormal follicle development can also be detected, and the common ones are as follows
[Unruptured follicle luteinization syndrome].
Luteinized unruptured follicle syndrome (LUFS) refers to a group of syndromes in which the follicles do not rupture and ovulation does not occur in the middle of the menstrual cycle despite regular menstrual cycles. In patients with luteinized unruptured follicle (LUF) cycle, if ovulation cycle is indicated by clinical methods of checking ovulation such as basal body temperature measurement, endometrial biopsy within 24 hours of menstruation, cervical mucus smear, etc., but in fact the egg is not expelled from the ovary, there is no ovulation spot on the ovarian surface on laparoscopy, but the body hormone level has reached luteinization.
The incidence of LUF is about 10% in normal menstrual cycles and up to 25%-43% in women with infertility, and it can occur repeatedly.
The sonographic features of LUF are: the follicles do not rupture until ovulation, they continue to increase in size with a thick wall and continue to grow during the luteal phase, with a maximum diameter of 7-200 px, and then shrink and disappear around the next menstrual period, with a few lasting for 2-6 months.
The differentiation between unruptured follicles and ovarian neoplasia in LUF cycle is simple and can be identified by observing 1~2 menstrual cycles.
Polycystic ovary syndrome]
Polycystic ovarian syndrome (PCOS) is a common endocrine disorder in women of reproductive age, which is characterized by polycystic ovarian changes with infertility, hirsutism, obesity, acne, menstrual disorders and other symptoms.
The main diagnostic criteria for PCOS are: low or no ovulation; clinical or biochemical hyperandrogenism; and ultrasound showing an increase in ovarian volume >10 ml and/or ≥12 follicles of 2-9 mm in diameter. The diagnosis can be made by having 2 of the above 3 items, but congenital adrenocortical hyperplasia, Cushing’s syndrome, and androgen-secreting tumors need to be excluded.
According to the diagnostic criteria of polycystic ovary syndrome, its ultrasound sonographic features are
1. enlarged ovaries with thick envelope.
2. interstitial echogenicity enhancement, which was previously considered to be the most sensitive and specific ultrasound sign in PCOS, but is now controversial.
3, 12 or more small follicles, similar in size and 2-9 mm in diameter, can be detected in the ovary, with no change in follicular morphology, size and number on dynamic observation. The small follicles are arranged in a circular bead shape under the ovarian envelope, which is called peripheral follicular type; the small follicles are scattered throughout the ovarian cortex in a honeycomb pattern, which is called common follicular type.
Small follicles ovulation type]
The dominant follicle appears during the follicular phase, but its development is delayed and it ruptures and ovulates when the follicle reaches 14-17 mm in diameter. The signs of ovulation are the same as those of the normal dominant follicle ovulation. The endometrial thickening is not obvious and the ovulation phase is hypoechoic. The “trilineage sign” does not appear and the endometrium shows moderate to strong echogenicity during the luteal phase.
Anovulatory type]
The endometrium of the uterus is the same as that of the small follicle ovulation type.