Fig. 8.1
Schematic drawing of the Muller and Wolf Ducts
If there is any disorder in the Wolffian duct, there will be impairment in the kidney formation, and the “floating” of the Müllerian duct, inducing a loss of anatomical uterine integrity – simultaneous genitourinary alterations.
Types of Malformations
The classifications recomended by the American Society for Reproductive Medicine are divided into seven categories and focus on the evaluation of the resulting uterine anatomy based on three types of alteration: absence of development and/or hypoplasia of the Mullerian ducts; incomplete fusion of the Mullerian ducts; or partial reabsorbtion of the interjacent myometrium when they fuse [12, 13].
The widespread acceptance of this form of classification is due to its simplicity, especially for the identification of the findings and the good correlation between anatomical alterations and the obstetric prognosis of patients [5]. However, some limitations are worth pointing out; these include the impracticality in cases of more complex malformations [3–6]; the fact that they are based on repercussions of fertility [5]; obstructive conditions resulting from aplasia and/or vaginal hypoplasia with normal uterus that are not represented; the fact that they do not provide objective aid to differentiate some subtypes of MDAs (e.g., differentiation between a subseptate uterus and arcuate uterus) [6]; and the fact that there is no determination of which diagnostic methods should be used in the radiological propedeutics [9].
Types of MDAs
Hypoplasia/agenisis, with Rokitansky syndrome the main disorder in this category
Unicornuate uterus
Didelphic uterus
Bicornuate uterus
Septate uterus
Arcuate uterus
Alterations resulting from diethylstilbestrol (DES) use
Morphology and Uterine Morphometry
There are useful morphological and morphometrical criteria in the differentiation among diverse sub-types, and also for the definition of normal uterus, as described below.
Anatomical Reference: Interostial Line
The interostial line is that formed when the extremities of the intramural regions of the uterine tubes join. The necessity to obtain images on a true coronal plane of the uterus for the adequate positioning of this line used in the measurements must be emphasized.
Measurement of the Fundal Indentation
This indentation is the distance between the interostial line and the apex of the serous uterine fundus. This measurement defines whether there is any defect in uterine fusion, which is useful in differentiating the septate uterus and bicornuate uterus.
Measurement of Depth of Impression in the Fundal Myometrium in the Uterine Cavity
This line defines the degree of deformity upon the endometrial cavity. It is used in the differentiation between the septate uterus and arcuate uterus (respecting the limits of normal fundal myoendometrial distance).
Normal Uterus
Normal uterine anatomy (Fig. 8.2)
Morphometrical criteria
Interostial line: joins both internal ostia of the uterine tubes
Yellow arrow: distance between interostial line and fundal serous. This distance must be greater than or equal to 0.5 cm
Red arrow: distance between interostial line and myoendometrial interface. This distance should be up to 1.0 cm
Fig. 8.2
Morphology and morphometry of normal uterus. The yellow arrows show the positioning of the interostial line. The white arrow shows the measurement of the distance between the interostial line and the fundal uterine serous. This distance should be from the center of the interostial line to the fundal uterine serous. From this measurement, fusion and reabsorption disorders are distinguished. The endometrial margin of the uterine fundus usually has a convex, rectilinear or even concave aspect. The degree of depth should be measured from the center of the interostial line, and should not be greater than 1.0 cm. (Figure courtesy: Athos Correia Sampaio, Federal University of Bahia)
Arcuate Uterus
Morphometrical criteria (Fig. 8.3)
Interostial line: joins both ostia of the uterine tubes
White arrow: distance between the interostial line and the fundal serous. This distance must be greater than or equal to 0.5 cm
Differentiates fusion and reabsorbtion disorders
Red arrow: distance between interostial line and the myoendometrial interface
The distance must be greater than or equal to 1.0 in and smaller than 1.5 cm
Fig. 8.3
The main difference between the normal uterus and the arcuate uterus is the degree of impression of the fundal myometrium on the endometrial cavity. (Figure courtesy: Athos Correia Sampaio, Federal University of Bahia)
Septate Uterus
Morphometrical criteria (Fig. 8.4)
Interostial line: joins both internal ostia of the uterine tubes
White arrow: distance between interostial line and fundal serous. This distance must be greater than or equal to 0.5 cm
Differentiates between fusion and reabsorbtion disorders
Red arrow: distance between interostial line and myoendometrial interface. This distance must be greater than 1.5 cm
Fig. 8.4
The length of the septum is variable. When it extends to the external ostia of the colon, it is considered complete septate. (Figure courtesy: Athos Correia Sampaio, Federal University of Bahia)
Bicornuate Uterus
Morphological criteria (Fig. 8.5)
Fork aspect
Morphometrical criteria
Interostial line: joins both ostia of the uterine tubes
White arrow: distance between interostial line and fundal serous. This distance should be less than 0.5 cm
Differentiates between fusion and reabsorbtion disorders
Biconuate and didelphic uterus: fusion disorders
Septate and arcuate uterus: absorbtion disorders
Fig. 8.5
The main morphometrical criterion is the distance from the interostial line to the apex of the fundal serous. When it is less than 0.5 cm, it is considered to have a fusion defect. The presence of a corporal junction between the two hemi-uteri, with or without myometrical reabsorpion between them, differentiates the bicornuate uterus from the didelphic one. There may be as much duplication as septation of the colon and/or the body of the uterus. (Figure courtesy: Athos Correia Sampaio, Federal University of Bahia)
Didelphic Uterus
Morphological criteria (Fig. 8.6)
There is no fusion between the two hemi-uteri
Variations in appearance and clinical condition resulting from duplication/patency of the vagina
Fig. 8.6
In this type of MDA, there is no corporal fusion between the two primordial uteri. A greater difficulty in interpretation may arise in cases where there is junction or fusion of the cervix, when it may resemble a bicornuate uterus. This often occurs with vaginal septum or duplication, which can trigger dysmenorrhea during the menstrual period. (Figure courtesy: Athos Correia Sampaio, Federal University of Bahia)
Unicornuate Uterus
Morphological criteria (Fig. 8.7)
Agenisis of one of the hemi-uteri
Incomplete fusion of the hypoplasic horn:
Without functioning endometrium
With functioning but non-communicating endometrium
With functioning and communicating endometrium
Fig. 8.7
Unicornuate uterus. (Figure courtesy: Athos Correia Sampaio, Federal University of Bahia)
Mayer-Rokitanski Syndrome
Morphological criteria (Fig. 8.8)
Agenisis or hypoplasia of both Müllerian ducts
Agenisis or hypoplasia of the superior two-thirds of the vagina
Ovaries with preserved dimensions and functionality, ensuring female sexual features
Fig. 8.8
Mayer-Rokitanski syndrome. (Figure courtesy: Athos Correia Sampaio, Federal University of Bahia)
Ultrasound and MR Images of Uterine Anatomy
3-D Ultrasound
The images obtained from ultrasound are produced by echoes formed by the interaction between the beams emitted by the transducers and the organs being studied. The greater the number of echoes produced, the whiter or clearer the structure appears in the images. Taking the quantity of echoes produced by the myometrium as a base, the echogenicity of all other uterine structures can be divided in the following way (Figs. 8.9, 8.10, and 8.11):
Hyperechogenic produces a higher number of echoes than the myometrium
Isoechogenic produces the same echo as the myometrium
Hypoechogenic produces a lower number of echoes than the myometrium
Anechoic does not produce echoes, and allows sound waves to pass through
Fig. 8.9
Hypoechogenic: produces a lower number of echoes than the myometrium
Fig. 8.10
(a) Image of the uterus in the sagittal plane (or “lateral view”) represented in schematic form in image c). (b) Image of the uterus in the coronal plane (or “anterior view”) represented in schematic form in image (d). The yellow arrows show thick and hyperechogenic endometrium (secretory phase)
Fig. 8.11
Three-dimensional reconstruction of the uterus from Fig. 8.7. Notice how both the external and internal fundal contours are well defined. The echogenic endometrium facilitates the visualization of the cavity contours, and thus makes the secretory phase the best time in which to carry out the examination
Ultrasound in the Assessment of MDAs
Carried out in the later stages of the menstrual cycle (endometrium more echogenic)
Duration 15–30 min
3-D >2-D
Does not use ionizing radiation
Limitations: assessment of rudimentary and non-communicating uterine horns
Magnetic Resonance
MR images are obtained from signals emitted by hydrogen protons after stimulation by way of radiofrequency pulses. Two types of images can be acquired: T1 weighted images and T2 weighted images. The latter are more widely used in uterine malformations, and are characterized mainly by the high-signal intensity emitted by structures containing liquid. Regarding the myometrium, the structures can thereby be classified in relation to its signal (Figs. 8.12, 8.13, and 8.14):
