This chapter should be cited as follows:
Pozzati F, Catena U, et al., Glob Libr Women's Med
ISSN: 1756-2228; DOI 10.3843/GLOWM.419593

The Continuous Textbook of Women’s Medicine Series – Gynecology Module

Volume 10

Ultrasound in gynecology

Volume Editors: Professor Antonia Testa, Agostino Gemelli University Hospital, Rome, Italy
Professor Simona Maria Fragomeni, Agostino Gemelli University Hospital, Rome, Italy

Chapter

Genital Tract Anomalies

First published: July 2025

Study Assessment Option

By answering four multiple-choice questions (randomly selected) after studying this chapter, readers can qualify for Continuing Professional Development points plus a Study Completion Certificate from GLOWM.
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CONGENITAL UTERINE MALFORMATIONS

Epidemiology

Congenital uterine malformations (CUMs) are structural anomalies of the female genital tract resulting from deviations or disruptions in embryological development. Although their exact etiology remains largely unknown, potential contributing factors include genetic mutations, hereditary influences and exposure to teratogenic substances during fetal life.

The reported prevalence of uterine anomalies varies widely depending on the studied population. According to a meta-analysis by Chan et al., which included 94 observational studies and 89,861 women, the overall prevalence of CUMs in the general population is 5.5%, increasing to 8% in infertile women, 13.3% in those with recurrent pregnancy loss, and reaching 24.5% in women with both risk factors.¹ CUMs can significantly impact reproductive outcomes, leading to infertility, recurrent miscarriage, preterm birth and abnormal fetal presentation. The clinical significance of these anomalies is largely dependent on their severity and specific anatomical characteristics, necessitating accurate diagnosis and classification to guide clinical management.

Embryology

The development of the female reproductive system begins in early embryogenesis with the formation, fusion and resorption of the Müllerian (paramesonephric) ducts, which give rise to the Fallopian tubes, uterus, cervix and upper third of the vagina. Any interruption or deviation in this process can result in congenital uterine anomalies.

CUMs can generally be categorized into three types based on the developmental defect:

• Defects in Müllerian duct formation (e.g. uterine agenesis, unicornuate uterus).
• Defects in Müllerian duct fusion (e.g. bicorporeal uterus).
• Defects in resorption of the central Müllerian septum (e.g. septate uterus).

Among these, the septate uterus is the most prevalent, with a mean incidence of 35% of all uterine abnormalities, and results from incomplete resorption of the central portion of the fused Müllerian ducts.²

Understanding the embryological origin of these malformations is crucial for both diagnosis and treatment, as surgical correction aims to restore normal uterine morphology and improve reproductive outcomes.

Diagnosis

The techniques used for diagnosis include gynecological examination, ultrasound, MRI, hysteroscopy and laparoscopy. One or more of these techniques may be necessary to achieve a diagnosis, depending on the complexity of the case.

Congenital anomalies of the female genital tract have been classified using various systems over the years. The 1988 American Fertility Society (AFS) classification system was long the most widely used worldwide.³ Despite its widespread application, this classification presented several limitations, including an excessive focus on uterine anomalies and the inability to classify complex cases. These shortcomings often led to delayed diagnoses, inadequate treatments and negative consequences for patients.

In 2021, the American Society for Reproductive Medicine (ASRM) expanded and updated the AFS classification system, incorporating all categories of Müllerian anomalies and providing more detailed diagnostic criteria.⁴ This classification identifies nine different categories of anomalies (Figure 1).

Currently, the most widely used system in Europe is the 2013 classification proposed by the European Society of Human Reproduction and Embryology (ESHRE) and the European Society of Gynaecological Endoscopy (ESGE).⁵ This classification, known as CONUTA (CONgenital UTerine Anomalies), includes five classes of uterine abnormality (from U1 to U5, considering U0 the normal uterus), four classes of cervical abnormality (from C1 to C4, considering C0 the normal cervix) and four classes of vaginal abnormality (from V1 to V4, considering V0 the normal vagina) (Table 1).

Transvaginal ultrasound (TVUS) is the first-line examination for assessing uterine morphology and is also used for intraoperative monitoring during corrective surgical treatment.

Two-dimensional transvaginal ultrasound (2D-TVUS) allows for the identification of findings suggestive of uterine malformation. However, the main limitation of 2D-TVUS is its inability to obtain a coronal view of the uterus, which is essential for an accurate diagnosis and to obtain measurements.

Three-dimensional transvaginal ultrasound (3D-TVUS) has revolutionized the diagnosis of uterine anomalies. With its high accuracy and reproducibility, it allows for a detailed assessment of uterine anatomy, overcoming many of the limitations of traditional two-dimensional ultrasound (2D-TVUS). One of the key advantages of 3D-TVUS is its ability to analyze the external contour of the uterus with a precision comparable to that of laparoscopy, as well as to detect anomalies that may be missed with 2D imaging.^6,7 The diagnostic accuracy of 3D-TVUS is particularly high, reaching approximately 91.6% for evaluating the external uterine shape and 100% for assessing the uterine cavity. These results are comparable to those achieved with magnetic resonance imaging (MRI).⁸

Below is a brief practical guide on how to obtain a high-quality coronal reconstruction of the uterus using 3D-TVUS (Figure 2).

Optimal timing for the exam is during the luteal phase of the menstrual cycle. At this stage, the secretory endometrium is hyperechogenic, providing excellent contrast against the surrounding myometrium and allowing for optimal visualization of the endometrial cavity.⁹

The coronal view of the uterus can be obtained from either a longitudinal or transverse scan. The key is to acquire a volume from a section in which the endometrium is clearly visible. Once the volume is acquired, navigation within it is essential for accurate reconstruction. How to rotate the images can be memorized using the following tips (Figure 3):

• Use the X-axis to rotate the uterus ‘like a roasted chicken’ (forward/backward roll).
• Use the Y-axis to rotate it ‘like a dancer’ (side-to-side twist).
• Use the Z-axis to rotate it ‘like a picture on the wall’ (tilting left/right).

To reconstruct the ideal coronal plane:

• Fix the endometrial cavity at the fundal level and rotate along the X-axis to visualize the cervical canal.
• Fix the endometrial cavity at the level of one tubal ostium and rotate along the Y-axis to bring the contralateral tubal ostium into view.
• Use the Z-axis to straighten the coronal plane of the uterus.

Once the orientation is optimized, scroll through the volume to select the most representative cut of the endometrial cavity for final analysis.

Septate uterus

The septate uterus is the most common congenital uterine malformation, characterized by a single uterine body with a normal external profile but an internal division into two parts. It arises from an incomplete resorption of the central portion of the fused Müllerian ducts. Failure of resorption of the tissue between the Müllerian ducts leads to the formation of a septum of variable extent within the uterine cavity, resulting in abnormal endouterine morphology.

Although the septum has been historically described as a poorly vascularized fibroelastic structure, recent histological studies, such as that of Sparac et al., have demonstrated that it is predominantly composed of fibromuscular tissue, with connective tissue predominating in 72.3% of cases and muscular component present in 27.6%. Additionally, power Doppler studies have confirmed significant vascularization in 71.22% of septa.¹⁰

Currently, three main classification systems for the septate uterus exist: ESHRE/ESGE (2013),⁵ ASRM (2016, 2021)^4,11 and CUME (2018).¹²

These classifications define measurable criteria and specific cut-offs for assessing fundal indentation on the coronal plane of the uterus (Figure 4).

According to the ESHRE/ESGE 2013 criteria, a diagnosis of a septate uterus is made when the fundal indentation exceeds 50% of the myometrial wall thickness on 3D ultrasound evaluation.⁵

Conversely, the 2016 ASRM classification establishes that a septate uterus is diagnosed when the distance from the interostial line to the apex of the indentation is ≥ 1.5 cm and the indentation angle is < 90°.¹¹ These criteria follow a combination of two previous definitions by Salim et al. and Ludwin et al.^13,14

In 2018, the CUME classification was introduced and defined a septate uterus when the indentation depth is ≥1 cm. This measurement was considered reproducible and clinically relevant by most experts.¹²

More recently, ASRM revised its criteria, lowering the cut-off for the internal indentation depth to 1 cm, aligning itself with the CUME classification.⁴

ESHRE/ESGE classification, currently one of the most widely used, distinguishes two subtypes of septate uterus (Figure 5):

• Partial septate uterus (class U2a): the septum extends variably into the uterine cavity without reaching the internal uterine orifice.
• Complete septate uterus (class U2b): the septum completely divides the uterine cavity reaching the internal uterine orifice.⁵

Diagnosis of the septate uterus is based on specific ultrasound measurements that allow for a detailed assessment of uterine anatomy. These measurements, performed using 3D-TVUS, enable accurate differentiation between a septate uterus and other congenital anomalies, as well as between a partial and a complete septate uterus.

The key measurements to be performed are reported in Figure 6 and include:

• Interostial distance: the length of the line between tubal ostia, which defines the width of the uterine cavity and serves as a reference for the following two measurements.
• Distance between the interostial line and the serosa: a parameter useful for measuring myometrial thickness relative to the external profile.
• Distance between the interostial line and the apex of the septum: the primary measurement for diagnosing the septate uterus. If this value is lower than the distance between the interostial line and the serosa, the diagnosis of a septate uterus is established according to ESHRE/ESGE criteria. A measurement greater than 1 cm supports the diagnosis of a septate uterus according to CUME and ASRM criteria.
• Fundal indentation angle: according to ASRM, an angle < 90° is indicative of a septate uterus, while CUME considers a < 140° cut-off.
• Cavity volume: an additional ultrasound parameter that may be useful for surgical planning and for assessing the impact of the malformation on fertility.

All these measurements are essential for an accurate diagnosis, for planning the most appropriate corrective surgical procedure, and for evaluating results after surgery.

Dysmorphic uterus

Dysmorphic uteri are Müllerian anomalies that have long been underestimated and misdiagnosed.¹⁵ They are characterized by a regular external uterine outline and an abnormal shape of the uterine cavity, excluding septa. They typically have smaller-than-normal dimensions.⁵

Dysmorphic uterus may be of primary origin (congenital), resulting from a non-fusion Müllerian anomaly during organogenesis, or acquired, secondary to intrauterine adhesion syndrome, adenomyosis or infectious causes such as tuberculosis.^16,17

The ASRM Classification does not consider dysmorphic uteri.⁴ According to the classification of AFS published in 1988, dysmorphic uteri belong to category VII, which includes uterine anomalies associated with exposure to diethylstilbestrol (DES), a synthetic non-steroidal estrogen, during embryonic development. DES was widely prescribed to prevent miscarriage until 1971.³

According to ESHRE/ESGE classification, dysmorphic uteri are identified with the code U1 (Figure 7).⁵ The category U1 includes:

• U1a or T-shaped uterus: characterized by a narrow uterine cavity due to thickened lateral walls with a correlation 2/3 uterine corpus and 1/3 cervix.
• U1b or uterus infantilis: characterized by a narrow uterine cavity without lateral wall thickening and an inverse correlation of 1/3 uterine corpus and 2/3 cervix.
• U1c or others: includes all minor deformities that does not meet the criteria for a T-shaped, infantilis or septate uterus (inner indentation at the fundal midline level of < 50% of the uterine wall thickness).

In 2019, Alonso Pacheco et al. proposed a subclassification of U1a (T-shaped) dysmorphic uteri using 3D ultrasound and hysteroscopy.^16,18

• T-shaped uterus: narrowing at the level of the middle third of the uterine cavity caused by thickened lateral walls with normal interostial distance (about 25 mm). On hysteroscopy the uterine cavity appears tubular and it is difficult to visualize the tubal ostia because they are lateralized (Figure 8).
• Y-shaped uterus: narrowing at the level of the middle third of the uterine cavity with reduced interostial distance caused by a small indentation at the level of the fundus that mimics an arcuate uterus. On hysteroscopy the uterine cavity is tubular and the uterine fundus has an indentation that prevents the visualization of the tubal ostium (Figure 9).
• I-shaped uterus: the lateral wall thickening extends from the internal cervical orifice to the level of the fundus. There is almost no difference between the upper, middle and lower parts of the uterine cavity. On hysteroscopy, the entire uterine cavity has a tubular shape up to the level of the fundus with interostial distance significantly reduced. Both tubal ostia are easily visualized because of their proximity (Figure 10).

It is important to differentiate the three subtypes of U1a dysmorphic uterus to recommend the best technique for optimal surgical treatment.¹⁸

T-shaped uterus diagnostic criteria

Over the years, various criteria have been proposed for the ultrasound diagnosis of T-shaped uterus, aiming to go beyond the purely subjective morphological ESHRE/ESGE classification.

Exacoustos

In 2015, Exacoustos et al. proposed new 3D-TVUS measurements for the diagnosis of T-shaped uterus¹⁹ including:

• fundal cavity width (W1) i.e. the distance between the two internal tubal ostia
• width of uterine cavity at corpus-isthmic level (W2)
• uterine fundal wall thickness (M) i.e. the distance between the interostial line and the external uterine serosa
• lateral angle between the corpus-isthmic cavity and the two fundal endometrial layers (A)
• indentation length (L) i.e. the distance from the tip of the fundal indentation to the interostial line (in the case of cavity fundal indentation)
• fundal indentation angle (α) i.e. the angle between the two endometrial layers.

Of these, measurement A was found to be significantly different in dysmorphic uteri compared to septate uteri (126.5° ± 11.4° vs 144.2° ± 10.2°), and the ratio W1/W2 was found to be significantly different in dysmorphic compared to normal uteri (5.4 ± 1.2 vs 2.33 ± 0.47).

CUME

In 2020, the Congenital Uterine Malformation by Experts (CUME) group published diagnostic ultrasound criteria for T-shaped uterus (Figure 11)⁹

• Lateral indentation angle ≤ 130°
• Lateral indentation depth ≥ 7 mm
• T-angle ≤ 40°

The diagnosis of a T-shaped uterus is made when all three criteria are met. If only two out of the three criteria are satisfied, the diagnosis is a borderline T-shaped uterus. In the absence of criteria or when only one of the three is present, the uterus is defined as normal/arcuate.⁹

Rule of 10

The Exacoustos and CUME diagnostic techniques have been shown to have good diagnostic accuracy, but their application is complex, requiring expert sonographers and specific training.¹⁷ Therefore, Alonso Pacheco et al., in 2021, proposed a new 3D ultrasonographic method to diagnose T-shaped uterus, called the ‘Rule of 10’, using the uterine coronal plane.¹⁷

The proposed method consists of drawing four lines and recording the length of three of them:

• R0: interostial line
• From the midpoint of R0 a perpendicular line 20 mm long
• R10: a parallel line to R0 in the uterine cavity at 10 mm below R0
• R20: a parallel line to R0 in the uterine cavity at 20 mm below R0

R10 and R20 are shorter in T-shaped uterus than in normal uteri. R10 ≤ 10 mm strongly increases the probability of having a T-shaped uterus. The ‘Rule of 10’ method proposes a diagnosis of T-shaped uterus when R10 ≤ 10 mm (Figure 12).

Despite the three diagnostic models proposed in recent years (Exacoustos, CUME, Rule of 10), the diagnosis of T-shaped uterus remains challenging. It is necessary to define clear and reproducible diagnostic criteria to avoid overestimating this uterine malformation and to identify the real impact that this condition has on fertility. In this regard, to review and compare the three diagnostic models and to identify the 3D-US measurements that best correlates with a diagnosis of T-shaped uterus, in 2025 Monaco et al. published a retrospective study including in the final analysis 50 patients with T-shaped uterus class U1a according to the ESHRE/ESGE classification of 2013.⁴⁵ The study identified lateral bulging (Ludwin et al.), the ratio between fundal cavity width (R0) and the isthmic cavity width (Wi) (Exacoustos et al.) and R10 of the Rule of 10 (Alonso Pacheco et al.) as the key parameters for the most accurate diagnosis of T-shaped uterus, in particular:

• lateral bulging ≥ 5 mm (instead of ≥ 7 mm of the CUME criteria)
• R0/Wi ≥ 5
• R10 ≤ 10 mm

According to the study of Monaco et al. of 2025, the diagnosis of T-shaped uterus can be made when at least two of the three criteria are met.⁴⁵

Y-shaped uterus diagnostic criteria

In 2024, Aslan et al. published a proposal for diagnostic criteria of Y-shaped uterus based on 3D-TVUS measurements²⁰ (Figure 13).

• Lateral indentation depths between 4 and 7 mm and fundal indentation depth between 5 and 9 mm
• Lateral indentation angles between 121° and 149° and fundal indentation angle between 121° and 145°
• Y-angles 25° to 46°

Bicorporeal uterus

The bicorporeal uterus is a congenital uterine anomaly resulting from incomplete fusion of the Müllerian ducts during fetal development. This anomaly leads to the formation of two partially or totally separated endometrial cavities.

The classification of bicorporeal uterus has evolved over time, with the two most used systems being the ESHRE/ESGE (2013) classification and the ASRM (2021) classification.^4,5 These classifications provide different criteria for defining and categorizing bicorporeal uteri.

The ESHRE/ESGE classification defines the bicorporeal uterus (Class U3) as a congenital anomaly characterized by an external fundal indentation greater than 50% of the myometrial thickness.⁵ This classification subdivides the anomaly into three distinct subtypes (Figure 14):

• Partial bicorporeal uterus (U3a): the fundal indentation exceeds 50% but does not reach the cervix.
• Complete bicorporeal uterus (U3b): the separation extends to the cervical level, leading to two functionally independent endometrial cavities.
• Bicorporeal-septate uterus (U3c): this mixed anomaly presents characteristics of both incomplete Müllerian fusion and partial septal resorption.

The ASRM 2021 classification defines a bicorporeal uterus based on a fundal indentation greater than 1 cm (Figure 15).⁴

The term ‘bicorporeal-septate uterus’ is introduced, but without clear diagnostic cut-offs to differentiate it from a standard bicorporeal uterus.

The diagnosis of a bicorporeal uterus is primarily based on imaging, with 3D-TVS being the gold standard. This technique allows for detailed visualization of the uterine morphology and permits measurement of the depth of the fundal indentation and the thickness of the septum, if present (Figure 16).

Distinguishing between bicorporeal and septate uterus is essential, as their clinical implications and management differ significantly (Figure 17). The external shape of the uterus is a key differentiating feature: a bicorporeal uterus presents with a deeply concave external fundal contour, while a septate uterus lacks this feature. Additionally, the endometrial cavities in a bicorporeal uterus tend to be widely spaced, in contrast to the closely approximated cavities characteristic of septate uteri.

Hemiuterus or unicornuate uterus

Hemiuterus, also known as unicornuate uterus, is defined as unilaterally developed uterus; the contralateral part could be either incompletely formed or absent (Figure 18).⁵ This type of Müllerian malformation results from a complete or partial developmental defect of one of the Müllerian ducts during embryogenesis. It is the uterine anomaly most associated with unilateral renal agenesis.

There are three main classification systems for unicornuate uterus.

Following the classification of AFS³ published in 1988, unicornuate uteri belong to Category II that is further divided into:

• communicating: two communicating uterine horns, one larger than the other
• non-communicating: two non-communicating uterine horns, one larger than the other
• no cavity: two uterine horns, the smaller one not cavitated
• no horn: a single uterine horn

According to the ESHRE/ESGE classification, hemiuteri are identified by the Class U4 (U: uterine anomaly, 4: hemiuterus) (Table 1).⁵ Class U4 is further divided into two sub-classes depending on the presence or not of a functional rudimentary cavity:

• U4a or hemiuterus with a rudimentary (functional) cavity characterized by the presence of a communicating or non-communicating functional contralateral horn.
• U4b or hemiuterus without rudimentary (functional) cavity characterized either by the presence of non-functional contralateral uterine horn or by aplasia of the contralateral part.

The ASRM Classification 2021⁴ classifies unicornuate uterus as:

• R/L unicornuate uterus
• R/L unicornuate with R/L distal atrophic uterine remnant
• R/L unicornuate with R/L distal uterine remnant with functional endometrium
• R/L unicornuate with R/L associated atrophic uterine remnant
• R/L unicornuate with R/L uterine horn communicating at the level of the cervix

As with all uterine malformations, in the case of unicornuate uteri, 3D US represents the gold standard for diagnosis. On 3D reconstruction, the profile of the uterine cavity resembles a hummingbird, where the beak corresponds to the distal portion of the ipsilateral Fallopian tube (Figure 19). In the case of a non-communicating rudimentary uterine horn (U4a), a condition of hematometra with or without ipsilateral hematosalpinx may be present and diagnosable through ultrasound examination (Figures 20–22).

CONGENITAL CERVICAL MALFORMATIONS

Embryology

Congenital cervical dysgenesis refers to anomalies in the development of the cervical canal during embryogenesis. By the end of the third month of pregnancy, the Müllerian ducts are formed, which give rise to key structures of the female reproductive system, including the uterus and vagina. Each Müllerian duct divides into three parts, and their fusion is essential for the creation of the uterus and cervix. A key process in this development is vacuolization, a mechanism that allows for the formation of the cervical canal and the upper part of the vagina. If disruptions occur during these critical phases, a malformed cervix can result. Several theories attempt to explain these anomalies in cervical formation: one suggests that there may be local atrophies in the cervical tissue, while another indicates that inadequate fusion of the Müllerian ducts could be responsible.^21,22 It is possible that a combination of both hypotheses contributes to various cases of congenital cervical dysgenesis.

Diagnosis

The classification introduced by AFS in 1988 categorizes cervical malformations as type 1B anomalies, which includes all cases of hypoplasia and agenesis of the female genital tract.³

ESHRE/ESGE provide a more detailed classification system, distinguishing cervical anomalies into several categories: normal (class C0), septate (class C1), double (class C2), incompletely formed or unilateral cervical aplasia (class C3), and complete cervical aplasia (class C4)⁵ (Table 1).

Septate cervix

Septate cervix is characterized by the presence of fibrotic tissue that divides the cervical canal into two separate parts. The septum can be complete, dividing the canal entirely, or it may involve only a portion of it. By using 2D ultrasound, the presence of two cervical canals can be suspected by scrolling the cervix from the lower to the upper part. The differential diagnosis with double cervix can be made only after completing ultrasound with vaginal inspection and diagnostic hysteroscopy. This condition can affect a woman's reproductive health and may cause complications such as difficulty in conception, miscarriage and labor complications. The severity of the condition can vary, and treatment typically involves surgical correction to remove the septum. If left untreated, it could continue to impact fertility and pregnancy outcomes.

Double cervix

Double cervix is characterized by the presence of two distinct cervices, each having a normal cervical canal. Using 2D ultrasound, the presence of two cervical canals can be suspected by scanning the cervix from the lower to the upper part. The differential diagnosis with a single septate cervix can be made only after completing ultrasound with a vaginal examination and diagnostic hysteroscopy. This malformation is frequently associated with vaginal anomalies, such as a septate vagina (Video 1). This condition is not amenable to surgical correction, leaving both cervices and cervical canals intact. If the anomaly is associated with a septate vagina and a septate uterus, both cervices are left intact, and the surgery involves only uterus and vagina (Figure 23).

Complete cervical aplasia

Cervical aplasia is an obstructive anomaly that should be considered in pubertal women presenting with primary amenorrhea and cyclical abdominal pain. Associated symptoms may include perineal, rectal or vesical pain, as well as cryptomenorrhea, which can negatively impact quality of life. Additionally, a higher prevalence of endometriosis may compromise the future functionality of the Fallopian tubes and ovaries, complicating any potential surgical interventions. It can be diagnosed with comprehensive clinical examination that includes inspection, palpation, ultrasound and magnetic resonance imaging (MRI). Palpation may reveal dilatations caused by menstrual flow obstructions, such as hematometra.²³ Since most patients are pubertal, a transabdominal scan may reveal a dilated uterus with hematometra. A transrectal approach can be proposed in compliant patients to conclude the diagnosis. With a transrectal approach, by using a cotton swab introduced within the vaginal canal, the operator can provide a measurement of the distance between the vaginal vault and the corpus of the uterus (Figure 24), to better plan treatment. Additionally, MRI offers highly reliable data on the cervix.²⁴

CONGENITAL VAGINAL MALFORMATIONS

Embryology

The vagina develops through a complex process involving various embryonic structures. The upper part of the vagina originates from the fusion of the Müllerian ducts, while the lower portion develops from the urogenital sinus. This occurs through the proliferation of the sinovaginal bulbs and the degeneration of the vaginal plate, with the canalization process typically completing by 20 weeks of gestation.²⁵

Longitudinal vaginal septa may cause dyspareunia, difficulty with penetrative intercourse, hygiene issues or, in the context of pregnancy, labor dystocia.

The diagnosis of a vaginal septum requires a thorough physical examination accompanied by 2D pelvic ultrasound. 3D ultrasound, hysterosalpingography and saline infusion sonohysterography, as well as magnetic resonance imaging (MRI), can be useful for a more comprehensive diagnosis.^26,27

Diagnosis

The 1988 AFS classification does not provide specific subclasses or nomenclature for vaginal anomalies.³

The 2013 ESHRE/ESGE classification (Table 1) defines four abnormal subclasses of vaginal defect.⁵ Considering V0 the normal vagina, the other subclasses include:

V1: longitudinal non-obstructing vaginal septum

This anomaly (Figure 25) is rare and associated with complex Müllerian anomalies, such as cervical defects with incomplete cervical canals and uterine anomalies, including septate uterus and bicorporeal uterus. The isolated form is even rarer.

V2: longitudinal obstructing vaginal septum

This type of anomaly presents with primary amenorrhea if there is a single uterine cavity; otherwise, it presents with normal menarche and progressive dysmenorrhea.

Ludwin et al. proposed a detailed classification of longitudinal vaginal septa based on observed clinical data, focusing on four main characteristics: (1) the completeness of the vaginal division (partial and complete types); (2) symmetry (symmetric and asymmetric positions); (3) association with the cervix (united and isolated forms); and (4) concomitant vaginal openings (normal and narrowed openings, such as those seen in cases of vaginal stenosis or persistent hymen) (Figure 26).²⁶

V3: transverse vaginal septum or imperforate hymen

Transverse vaginal septa are rare congenital abnormalities of the vagina with a reported incidence varying from 1 : 2100 to 1 : 72 000.²⁸ These septa can occur at various levels within the vagina, although they are most often located in the upper two-thirds. Thicker septa are typically found closer to the uterine cervix and, in some instances, a notable portion of the vagina may be atretic.²⁹

Transverse vaginal septa can be classified into two types: complete and partial (or incomplete).

A complete vaginal septum is often diagnosed during puberty, as individuals with this condition typically present with primary amenorrhea and cyclical pelvic pain due to hematocolpos. Transabdominal ultrasound can reveal the distended upper part of the vagina, the cervical canal and the uterine cavity. Transvaginal or transrectal ultrasound may also be informative, though these techniques may be limited by pressure from the probe. MRI provides a comprehensive view of the vaginal tract. Infusing ultrasound gel through the vaginal introitus can enhance visualization of the septum on MRI and allows for measurement of its thickness and position.³⁰

In contrast, a partial septum is usually asymptomatic because a central opening allows for menstruation. However, if the partial septum is in the lower third of the vagina, it may cause dyspareunia. Partial septum is often discovered incidentally during a gynecological examination or when the patient is being assessed in labor.³¹

V4: vaginal aplasia (complete or partial)

In cases of partial vaginal aplasia, a transverse vaginal septum may be suspected. The differential diagnosis is crucial, as different surgical approaches are required depending on the condition. MRI is always recommended in these cases, as ultrasound can sometimes underestimate the extent of the defect.

COMPLEX GENITAL TRACT ANOMALIES

When approaching a patient with a suspected complex anomaly, it is important to consider all the potential pathologies that may affect the genital tract. The most effective way to assess the anatomical condition is through an integrated approach that includes a bimanual examination (transvaginal or transrectal), ultrasound (transvaginal, transrectal and transabdominal), MRI (performed by a radiologist with expertise in this field) and hysteroscopy. Close collaboration among all specialists is essential to achieve an accurate diagnosis and to plan the most appropriate treatment in the most suitable setting. The use of the ESHRE/ESGE classification system allows for a more comprehensive description of the full range of possible anatomical conditions. MRI is more frequently required in this selected patient population. In this section, we describe rare conditions collectively referred to as 'complex genital tract anomalies'.

Mayer-Rokitansky-Küster-Hauser syndrome

Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is characterized by the absence of the uterus and vagina in an otherwise phenotypically normal woman with a 46,XX karyotype, resulting from the failed embryologic development of the Müllerian ducts. The incidence of MRKH has been estimated to be 1 in 4000 to 5000 female newborns.³²

There are two types of MRKH syndrome:

• Type I MRKH syndrome (isolated uterovaginal aplasia) is characterized by agenesis of the uterus and upper part of the vagina, with normal Fallopian tubes and no extragenital abnormalities.
• Type II MRKH syndrome refers to cases of Müllerian agenesis associated with extragenital abnormalities, such as musculoskeletal defects or renal anomalies (e.g. renal ectopia, renal agenesis, renal hypoplasia or horseshoe kidney) or ear abnormalities.³³

The etiopathogenesis of MRKH syndrome remains unknown. Although the exact cause is unclear, it is likely to be related to embryogenesis, particularly in the third week, as the genitourinary system develops from the intermediate mesoderm. During this phase, the mesonephric ducts of Wolff descend and reach the Müllerian tubercle on the midline, with the caudal portions of the Müllerian ducts forming the uterus and the upper part of the vagina.^34,35

MRKH syndrome has complete penetrance but variable expressivity, resulting in markedly different phenotypic expressions. External genitalia are normally developed. The hymen is usually absent. The vagina may be completely absent, present as a shallow fovea or normally developed in the lower third, ending at the junction between the lower third and upper two-thirds due to differences in embryological development. The uterus can be entirely absent or may be present as a rudimentary structure located behind the bladder in the middle of the pelvis. The size of the uterus varies significantly, and the myometrium may be affected by fibroids. The endometrium is usually absent but can occasionally be present. Müllerian remnants are often found laterally in the pelvis, near the Fallopian tube. Ovaries usually function normally and may be in the typical anatomical position or cranialized beyond the pelvis.

MRKH is commonly diagnosed in adolescence or early adulthood, often when a patient presents with primary amenorrhea. If an active endometrium is present, the patient may seek a specialist due to cyclic or chronic abdominal pain and primary amenorrhea. During a gynecological examination, the absence of the vagina is noted, although a vaginal dimple of varying lengths may be present.

Ultrasound is the first-line diagnostic tool for MRKH. MRI and diagnostic laparoscopy may be necessary in cases of more complex anomalies.

The existing classification systems do not fully reflect the heterogeneity of clinical presentations.

According to the ASRM classification (1988), MRKH is classified as Class 1E, while in the 2021 revision, it is classified simply as Müllerian agenesis.⁴

In the ESHRE ESGE classification (2013), MRKH is classified as U5(a) if a rudimentary cavity is present and U5(b) if the cavity is absent. In this classification, the cervix and vagina are classified independently, so MRKH is classified as cervical aplasia (C4) and vaginal aplasia (V4).⁵

A separate and more accurate classification system for MRKH syndrome could be useful to describe the various morphological patterns encountered in routine clinical practice.

Obstructed hemivagina and ipsilateral renal anomaly (OHVIRA)

Complete bicorporeal uterus, double cervix and obstructive longitudinal vaginal septum (classified as U3bC2V2 according to ESHRE/ESGE classification) is a rare congenital anomaly of the genital tract. This condition is typically associated with ipsilateral renal agenesis and is known as Herlyn-Werner-Wunderlich syndrome or OHVIRA (Obstructed HemiVagina and Ipsilateral Renal Anomaly) syndrome. The primary symptoms include dysmenorrhea and pelvic pain, which usually manifest after menarche due to hematocolpos in the obstructed hemivagina. Diagnosis is often challenging and frequently delayed. Early detection and surgical drainage of the hematocolpos are essential for symptom relief and prevention of complications. Various surgical approaches have been described, with vaginoplasty and septal resection being the recommended treatment.³⁶

Delayed or improper diagnosis of OHVIRA syndrome may result in complications. With the aim of reducing the time required to diagnose OHVIRA and allowing for the treatment of patients before the onset of symptoms, in 2025 Ludwin et al.³⁷ proposed a three-step ultrasound-based screening method:

• Prenatal assessment: evaluation of the fetal genital tract following the diagnosis of a renal anomaly (e.g. renal agenesis).
• Neonatal assessment: within the first 2 weeks of birth, after the reduction of maternal estrogenic influence.
• Assessment at menarche in adolescence: enables evaluation of hemi-hematocolpos and serves as the definitive confirmation of the diagnosis, allowing for timely surgical planning.
  

According to the proposed algorithm, the prenatal diagnosis of renal agenesis in female fetuses should be an indication for mandatory screening of OHVIRA syndrome following the three steps. It should be emphasized that the evaluation of Müllerian malformations in the fetus and neonate is still challenging.

Ultrasound is the method of choice for the diagnosis of OHVIRA syndrome. In pediatric and adolescent virgo girls, transabdominal ultrasound is the first-line approach. 3D-US reconstruction is highly recommended. Transrectal ultrasound can be offered to the patient, allowing for visualization of the pelvis comparable to that of the transvaginal approach. MRI should be the second-line method.

Robert’s uterus

Robert’s uterus is a less commonly discussed uterine malformation, also referred to as an asymmetric septate uterus. It is characterized by the presence of a blind-ending uterine hemicavity lined by a partial functional endometrium (Figure 27). In some cases, the cervix may also be malformed or duplicated, which can complicate the condition further. Robert’s uterus is often associated with progressive abdominal pain and dysmenorrhea caused by hematometra.^38,39

These symptoms are attributed to the partial functional endometrium lining the blind-ending uterine cavity, which connects to the ipsilateral Fallopian tube.^38,40,41 This anatomical configuration leads to the accumulation of menstrual blood in the cavity, causing menstrual pain. Additionally, some blood may exit into the pelvic cavity via the ipsilateral Fallopian tube, contributing to the development of secondary endometriosis, endometriotic cysts and pelvic adhesions.⁴² These factors help explain symptoms such as dysmenorrhea, bilateral ovarian endometriotic cysts, intestinal adhesions,and adenomyosis, as experienced by our patient.

Robert’s uterus is classified under the ASRM’s Müllerian Anomaly Classification (2021) as a uterine septum.⁴ This classification recognizes the presence of a longitudinal septum dividing the uterine cavity. According to the ESHRE/ESGE classification, this malformation is categorized as U6, indicating an unclassified uterine malformation. However, some practitioners may define this condition as a complete septate uterus (U2b), which is characterized by unilateral cervical hypoplasia (C3) and a normal vagina (V0).⁵

From an imaging perspective, differentiating Robert’s uterus from an accessory cavitated uterine mass can be challenging due to their similarities.⁴³ Both conditions involve a uterus with a blind cavity that produces menstrual blood.

Treatment depends on the severity of the condition and the symptoms the woman is experiencing. For many women, hysteroscopic surgery to remove the uterine septum is necessary to alleviate symptoms and attempt pregnancy. The procedure is challenging and involves transrectally guided hysteroscopic metroplasty, in which an incision is made in the myometrium between two parts of the cavity using a resectoscope and Collins electrode. The surgery results in a single uterine cavity with a normal fundus (Figure 28).⁴⁴

The prognosis for women with Robert’s uterus depends on the severity of the malformation and how well it is managed. Many women with a mild form of the condition can have successful pregnancies, particularly with surgical intervention. However, if the malformation is more severe, the risk of complications may remain elevated.

PRACTICE RECOMMENDATIONS

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