(1)
Department of Fetal Medicine and Obstetric & Gynecological Ultrasound, Manipal Hospital, Bangalore, Karnataka, India
Evaluation of uterine anomalies can be confusing because of the various diagnostic ultrasound criteria and available classifications. In this chapter, we have primarily followed the popular AFS classification. In order to better understand the types of anomalies, the chapter initially deals with embryopathogenesis. A brief account of the basic diagnostic criteria is initially discussed. Following this, the diagnosis of each type of anomaly, based on these criteria, is provided. The last part of this chapter deals with the evaluation of the cervix and vagina for congenital anomalies, which is not focused upon most often in literature, primarily because it is believed to be suboptimally assessed on regular TVS. Cervical and vaginalanomalies are generally associated with uterine anomalies. Here the fine points for ultrasound diagnosis of cervical and vaginal anomalies, including the useful novel use of GSV for accurate evaluation of these conditions, are provided.
The prevalence of uterine anomalies is believed to be between 4% and 7 % (Grimbizis and Campo 2012). The prevalence is higher in select populations, like recurrent aborters.
There is a higher incidence of associated renal abnormalities in women with uterine anomalies, because of related embryological development of these organs.
Many of these women with uterine anomalies are asymptomatic. Some may, however, present with the followingclinical manifestations:
- 1.
Reproductive health – particularly recurrent pregnancy losses. In subseptate uterus, there is an increased risk of first trimester loss. In arcuate uterus, there is an increased risk of second trimester loss and preterm labour. Abnormal fetal presentation is more common in women with uterine anomalies. Conceiving, however, is generally not an issue in patients with uterine anomalies.
- 2.
Adolescent health issues like pain, as seen in haematocolpos and a non-communicating uterine horn.
- 3.
Life-threatening emergencies like rupture of a cornual pregnancy.
12.1 Embryopathogenesis (Figs. 12.1, 12.2)
The uterus develops from two Mullerian (paramesonephric) ducts. Their lower ends fuse to form the upper two-third of the vagina, cervix and uterus. Their upper ends do not fuse, and they form the two fallopian tubes. The lower one-third of the vagina develops from the urogenital sinus. Fusion of the two Mullerian ducts occurs from below upwards. Following fusion, the intervening septum gets resorbed to form a common uterine cavity. The resorption also occurs from below, upwards. If there is any abnormality in the process of development, fusion or resorption, it results in a uterine anomaly.
Fig. 12.1
Stages of embryological development of the female genital tract. (a) The uterus develops from the two Mullerian ducts (arrows). (b) The two ducts fuse together beginning from the lower end to form the uterus and the upper two-third of the vagina. The upper non-fused parts give rise to the fallopian tubes. (c) The intervening septum between the two fused ducts gradually gets resorbed starting from the lower end, moving upwards. (d) Single uterine cavity formed following resorption of the septum. (e) The upper two-third of the vagina arises from the Mullerian duct and the lower one-third from the urogenital sinus. (f) The transverse septum between the upper two-third and the lower one-third of the vagina gets resorbed forming a single vaginal cavity
The American Fertility Society (AFS) classification (Figs. 12.2 and 12.3), which is the most popular classification of uterine anomalies (and is followed in this chapter), is based on the stage of arrest of development, fusion or resorption in the above process.
Fig 12.2
AFS classification of uterine anomalies: based on the stage of arrest. (a) If there is arrest prior to complete development of the two Mullerian ducts, it can result in agenesis or unicornuate uterus. (b) If there is arrest prior to complete fusion of the two Mullerian ducts, it can result in didelphys or bicornuate uterus. (c) If there is arrest prior to complete resorption of the intervening septum, it can result in septate or arcuate uterus
Fig. 12.3
AFS classification of uterine anomalies
12.2 AFS Classification of Uterine Anomalies (Figs. 12.2 and 12.3)
Underdeveloped
Class I – Mullerian agenesis or hypoplasia; cases with agenesis or hypoplasia of part or whole of the Mullerian ducts
Class II – cases with underdevelopment of one of the Mullerian ducts resulting in a unicornuate uterus, which could again be of four types, as shown in Fig. 12.3
Fusion DefectClass III – complete lack of fusion, resulting in a didelphys uterus
Class IV – partial defect in fusion, resulting in a bicornuate uterus
Resorption DefectClass V – septate uterus (complete absence of resorption) and subseptate uterus (partial resorption defect).
Class VI – arcuate uterus; the fusion defect is minimal as a result of which there is a slight indentation of the uterine cavity.
Class VII – a ‘T-shaped’ uterus which could be the result of intrauterine exposure to diethylstilbestrol.
12.3 Approach to Diagnosing a Uterine Anomaly
Diagnosis of uterine anomalies requires an assessment of the external fundal contour and an assessment of the shape of the inner uterine cavity.
The external fundal contour can be assessed at laparotomy and laparoscopy.
The inner uterine cavity can be assessed by hysteroscopy or hysterosalpingography (HSG).
However, the only modalities that can assess both the cavity and the external fundal contour are ultrasound and MRI.
Ultrasound is the primary diagnostic modality of choice because of its lower cost and easy availability.
Assessment in pregnancy is not likely to be accurate because of the altered shape and dimensions, which could be because of an eccentrically placed gestational sac. Patients should therefore be called about 2–3 months after abortion or delivery for identification and correct classification of any existent or suspected uterine anomaly.
Two-dimensional (2D) greyscale imaging helps raise the suspicion of a uterine anomaly and in some cases may even help to confirm the presence of a uterine anomaly. However, three-dimensional (3D) imaging is essential in confirming and diagnosing the type of uterine anomaly. The best time for evaluation is the secretory phase of the menstrual cycle, because the endometrium lining of the uterine cavity at that time is fluffy and oedematous and shows up well on 3D ultrasound.
On 2D ultrasound, findings in women with uterine anomalies are:
Broad transverse diameter of the uterus.
On transverse section, the endometrial cavity is seen splitting into two as one moves upwards from the cervix to the fundus.
In some cases, two separate uterine bodies are seen (more obvious on transverse section at TAS).
In a longitudinal section scan, on moving from one cornua to the other cornua, the endometrial length in the midline appears shorter, while on both cornual ends it appears longer.
Fig. 12.4
Longitudinal and transverse section of the uterus showing increased transverse dimension of the uterus (6 cm) with two endometrial cavities
Fig. 12.5
TVS showing increased transverse diameter of the uterus with two endometrial cavities (arrows)
3D ultrasound has been discussed in Chap. 2. Some points dealing with evaluation of uterine anomalies are being mentioned:
The best time to evaluate the uterine anomaly is the secretory phase (when the endometrium is thick and oedematous), and the best time to evaluate the cervix is mid-cycle (around ovulation – when the cervix has abundant mucous).
Typically, the best plane to take a 3D volume is the sagittal section of the uterus in the midline (the section where the endometrial length is minimal). The angle of sweep should be made as wide as possible.
In cases with a broad fundus or two uterine horns placed far apart, the 3D sweep should be taken in a transverse section.
Because the cervix and uterine body are often in different planes, they may have to be evaluated separately with rendering in two separate planes.
Polyline is an effective new technique for simultaneous assessment of the cervical and uterine cavities in a single rendered image.
Evaluation of the cervix and vagina is suboptimal on regular TVS because of the proximity of these structures to the probe and the collapsed vaginal walls. For evaluation of the cervix and vagina, the probe may have to be withdrawn a little for better visualisation. Gel sonovaginography (GSV) is a great technique to evaluate the cervix and the vagina (discussed in Chap. 2).
It is sometimes easier to assess the uterine anomaly with 3D on a transabdominal scan with a full bladder, as compared to a transvaginal scan, because the uterus (its two horns and the cervix) gets more stretched and straightened out with a full bladder, making the rendered image much clearer.
On 3D ultrasound, the external fundal contour and the inner uterine cavity are both well visualised. A normal uterus has a convex external fundal contour, and the upper end of the uterine cavity is flat (Fig. 12.6).
Fig. 12.6
3D rendered coronal image of a normal uterus showing a convex external fundal contour (short arrow) and the triangular shape of the inner uterine cavity of the uterus with the upper end of the uterine cavity being flat (long arrow)
- A.
The external fundal contour is considered abnormal if:
The indentation of the myometrium in the midline is more than or equal to 10 mm.
The uterine fundus crosses below the line joining the upper end of the cavities on both sides or is less than or equal to 5 mm from it (Troiano and McCarthy 2004). This is the method most accepted today and is followed in this chapter (Figs. 12.7 and 12.8).
The indentation of the myometrium in the midline is more than 50 % of the uterine wall thickness (the mean thickness of the anterior and posterior walls in the sagittal section). This is based on ESHRE classification.
Fig. 12.7
Troiano and McCarthy’s method of evaluating the external contour of the uterine fundus. The uterine fundus is considered abnormal (a) if it crosses below the line joining the upper end of the cavities on both sides and (b) if it is less than or equal to 5 mm from it. (c) If the uterine fundus is more than 5 mm from this line, the external contour of the fundus is considered normal
Fig. 12.8
Distance between the uterine fundus and the line joining the upper end of the cavities on both sides is measured to assess whether the external fundal contour is normal. If it is less than or equal to 5 mm, this would be considered as abnormal external fundal contour and the anomaly would be labelled as a bicornuate uterus. If it is more than 5 mm, the external fundal contour is considered normal and the anomaly would be labelled as a septate uterus
- B.
Shape of the uterine cavity is considered abnormal if there is any indentation in its superior outline.
It is important to differentiate between arcuate and septate/subseptate uterus. The table below shows the various methods used, of which the angle at the centre is most commonly used for evaluation (Fig. 12.9).
Fig. 12.9
Shape of the uterine cavity based on the angle at the centre: (a) arcuate (more than or equal to 90°) and (b) subseptate (less than90°). Shape of the uterine cavity based on the depth of indentation of the cavity: (c) arcuate (less than 1.5 cm) and (d) subseptate (more than or equal to 1.5 cm)
ARCUATE
1. Angle at the centre is more than or equal to 90 degree2. Indentation of less than 1.5 cm3. Indentation of less than 50% uterine wall thickness
SEPTATE / SUBSEPTATE1. Angle at the centre is less than 90 degree2. Indentation of more than or equal to1.5 cm3. Indentation of more than 50% uterine wall thickness
12.4 Types of Uterine Anomalies
12.4.1 Arcuate Uterus (Fig. 12.10)
- A.
External fundal contour:
Normal
- B.
Shape of the uterine cavity:
Abnormal – indentation seen
Angle at the centre between the two uterine cavities is obtuse (more than or equal to 90°)
Fig. 12.10
Different cases of arcuate uterus with normal external fundal contour and indentation of the uterine cavity with angle more than or equal to 90°
The arcuate uterus is generally compatible with normal reproductive outcome. It is considered by some to be a normal anatomical variant. It is proposed that if the ratio of the height to the length is less than 10 % (Fig. 12.11), it is not believed to be of clinical significance. It does not exist as a separate entity from a septate uterus in the new ESHRE classification.
