Anovulatory group
Type
Hormone levels
Prevalence
Causes
Clinical features
WHO I
Hypogonadotropic
FH↓↓
5–10 %
Pituitary destruction
Abnormal BMI (<20, 30)
Hypogonadism
LH↓↓
Anorexia nervosa
Amenorrhoea
E2↓↓↓
Excessive exercise
Progesterone test negative
AMH↓
Do not response to CC or AI
Response to gonadotropins
WHO II
Normogonadotropic
FSH N
75–85 %
PCOS
BMI normal or >25
Normogonadism
LH N or ↑↑
LUF
Oligomenorrhoea
E2N
Progesterone test positive
AMH N
Response to CC or Al
Androgens↑↑ (in PCOS)
Response to metformin (in case of PCOS)
WHO III
Hypergonadotropic
LH↑ or N
10–20 %
Primary ovarian insufficiency
Normal BMI
Hypogonadism
FSH↑↑↑
CMT, RT, surgery
Amenorrhoea
E2↓
Progesterone test negative
AMH↓
No response to CC, Al or gonadotropins
Hyperprolactinaemia
PRL↑↑
5 %
Pituitary adenoma
Normal BMI
LH N
Pituitary dysfunction
Oligomenorrhoea
FSH N
Dopamine insufficiency
Progesterone test positive
E2N
Response to PRL normalisation
AMH N
In this chapter, we shall review how ultrasound may be used for assessing the ovary in women with anovulation.
2.2 How We Do It?
2.2.1 Technique
Transvaginal ultrasound (TVS) is the best approach for assessing the ovary and the endometrium. In the case of women in whom TVS cannot be performed (e.g. women with virgo intacta), transrectal ultrasound is a very good alternative since it provides quite similar images to TVS. Transabdominal ultrasound may be also an option, but the resolution of the ultrasound image uses to be worse.
Transvaginal ultrasound does not require any preparation before the procedure is done, except the mandatory use of a condom or ultrasound sheath for covering the ultrasound probe and the cleaning by any kind of disinfectant of the probe prior to be used in a new patient.
For transrectal ultrasound, rectal cleansing is recommended before ultrasound is performed and the same measures for probe covering than TVS are mandatory.
For transabdominal ultrasound, full bladder is required.
After inserting the endovaginal probe into the vagina, a thorough scanning of the pelvis is always advised including, obviously, the uterus and ovaries, for ruling out the presence of any uterine or adnexal pathology, such as congenital uterine anomalies, fibroids, adenomyosis or adnexal masses.
Once ruled out uterine and adnexal pathology attention should be paid to the ovaries and the endometrium.
The ovaries should be assessed completely by slight movement of the vaginal probe (Video 2.1). If a three-dimensional (3D) volume is acquired, the 3D bow should be adjusted to the ovary, usually as small-angle sweep can be used (35–40°) (Video 2.2).
The uterus should be also assessed by scanning side to side in the sagittal plane and from the cervix to the fundus in the transverse plane (Video 2.3). If a 3D volume of the uterus is acquired, the 3D box should be adjusted for including the whole uterus or at least the uterine corpus, and a wider 3D sweep angle is needed (90–120°) (Video 2.4).
2.2.2 Assessment of the Ovary
2.2.2.1 Biometry/Volume Calculation
The basic assessment of the ovary is measuring its size. The three orthogonal planes should be measured (Fig. 2.1). Using the prolate ellipsoid formula (height × width × length × 0.5233), the ovarian volume can be calculated and expressed in mL.
Fig. 2.1
Measuring the ovary using 2D transvaginal ultrasound
Ovarian volume may be also calculated using a 3D volume. Current evidence shows that the best method for calculating ovarian volume is the virtual organ computer-aided analysis (VOCALTM) method. This method consists of estimating the volume of the ovary by outlining the ovarian borders using a rotational method, visualising different ovarian planes at given rotational degrees over the axis X, Y or Z (Fig. 2.2).
Fig. 2.2
Ovarian volume estimation using 3D ultrasound with VOCAL software
2.2.2.2 Antral Follicle Count
Antral follicle count (AFC) consists of counting all antral follicles visible within the ovary.
This issue is explained in Chap. 1. Please read this chapter for further information.
2.2.2.3 Doppler Assessment
The use of Doppler ultrasound allows the assessment of ovarian vascularisation. During 2D real-time ultrasound, the amount of flow in ovarian stroma, dominant/preovulatory follicle and corpus luteum can be subjectively assessed. Additionally, pulsed Doppler may be used for assessing vascular impedance of ovarian stroma, dominant/preovulatory follicle and corpus luteum vessels.
For assessing ovarian vascularisation, the colour/power Doppler window is activated over the ovary to identify stromal, preovulatory follicle (Fig. 2.3) or corpus luteum (Fig. 2.4) vessels. Then, pulsed Doppler gate is activated, and the flow velocity waveform (FVW) is obtained for calculating peak systolic velocity (PSV), resistance index (RI) and pulsatility index (PI).
Fig. 2.3
Transvaginal colour Doppler ultrasound showing perifollicular flow
Fig. 2.4
Transvaginal colour Doppler ultrasound showing the characteristic “ring of fire” of vessels surrounding the corpus luteum
In normal cycles the vascularisation increases after ovulation being maximum at 7 days post-ovulation. This is called “luteal conversion” of intraovarian FVW [6] (Figs. 2.5 and 2.6). The main problem for this assessment is its reproducibility between observers [7]. Three-dimensional ultrasound has been also used for assessing ovarian vascularisation. Using VOCALTM software, we can calculate three vascular indices, namely, vascularisation index (VI), flow index (FI) and vascularisation-flow index (VFI). These indices represent, theoretically, the amount of vessels (VI), the amount of flow (FI) and perfusion (VFI) [12]. However, this concept has been challenged [8]. Additionally, some machine settings and depth affect significantly the estimation of these indices [9].
Fig. 2.5
Transvaginal pulsed Doppler ultrasound showing the flow velocity waveform from perifollicular vessels from a periovulatory follicle. Note high-resistance flow (RI: 0.60)
Fig. 2.6
Transvaginal pulsed Doppler ultrasound showing the flow velocity waveform from a corpus luteum. Note the increase in telediastolic velocity
Favourably, the reproducibility of this approach has been shown to be good [10].
A more recent method, based on spatio-temporal correlation image, has been proposed [11]. This method allows the calculation of the so-called volumetric pulsatility index [12]. Theoretically this approach overcomes some of the problems released to static 3D-PD assessment. However, this approach is still in investigation and it has not been translated into clinical practice.
2.2.3 Assessment of the Endometrium
The basic assessment of the endometrium consists of measuring the endometrial thickness. This should be done in the sagittal plane of the uterus, including both endometrial layers (if an intrauterine collection is present, it must be excluded from measurement). The measurement should be done at the level of the maximum endometrial thickness (Fig. 2.7). This measurement is highly reproducible [13]. An additional important issue is the assessment of endometrial echogenicity. This refers to the subjective analysis of echogenic texture of the endometrium. 3D ultrasound allows the estimation of the endometrial volume. The best way for estimating endometrial volume is the use of VOCALTM software. The use of 3D ultrasound for estimating endometrial volume has been validated [14] and it is reproducible [15].
Fig. 2.7
Transvaginal ultrasound showing endometrial thickness measurement
2.2.4 Interpreting Findings
The use of ultrasound in combination with laboratory analysis has become essential for assessing anovulatory disorders.
2.2.4.1 Normal Findings
For interpreting properly the findings of ultrasound evaluation, it is important to know what are the normal findings in both ovarian and endometrial cycles. Ideally, the assessment of the ovary and endometrium by ultrasound should be done throughout a menstrual cycle, starting on the 4th–7th day of the cycle and going on performing an ultrasound scan every 48 hours until confirming ovulation; a final ultrasound scan should be performed 7 days after ovulation. This approach will allow the assessment of the follicle and endometrium dynamics.
In the normal cycle, the ovaries at 4th–7th day of the cycle appear as oval structures containing antral follicles (Fig. 2.8). AFC should be done in this scan, as well as ovarian volume estimation. Normal AFC is 6–10 follicles per ovary and ovarian volume is 3–10 mL.
