Chauhan AR
Mullerian duct anomalies
(MDAs) are a complex group of uterine anomalies that present in adolescence or
later, and affect a woman’s sexual and reproductive health. Though the reported
incidence is 0.1 – 3.5% in the general population, we encounter a spectrum of
anomalies at the tertiary care level, some of which have been presented in
previous editions of this journal. MDAs are often only diagnosed when
evaluating menstrual irregularities (primary or secondary amenorrhea,
dysmenorrhea, cyclical abdominal pain) or infertility. The reported incidence
varies from 3 -6% in women with infertility, to as high as 5-10% in patients
with bad obstetric history. The practicing gynecologist may not
routinely encounter these anomalies, and should be aware of the various types
and classifications, diagnosis, surgical management and psychological and
sexual consequences. This article addresses the recent proposed classification
system, three-dimensional ultrasonography (3D-USG) and MRI in diagnosis, and
endoscopic surgical correction in selected cases.
Normal development of
the female reproductive tract involves a series of complex interactions where
the embryologic paired mullerian ducts originating from mesoderm, undergo
dynamic processes of differentiation, migration, fusion and resorption (or
canalization) to form the uterus, cervix, fallopian tubes and superior third of
the vagina. MDAs can occur when there is
a dysregulation or disruption in any of these normal processes. Although the
urogenital sinus (UGS) arises from the endoderm, the developmental fate of both
the mullerian ducts and UGS are closely linked; the lower two-thirds of vagina
arise from the UGS. Concurrently, abnormalities of the urinary system and axial
skeleton are associated with MDAs, and are sometimes first diagnosed when
patients are evaluated for menstrual complaints or infertility.
The developmental stages
when interruptions occur are well established, and defects are grouped
according to the failed developmental mechanism that gives rise to a particular
malformation. For easy understanding, it is practical to divide mullerian
development into three sequential stages, namely development, fusion and degeneration
and hence three general categories of failure, namely, nondevelopment,
nonfusion, and nondegeneration.
Nondevelopment: Early arrest of
development results in complete uterine agenesis
(Mayer-Rokitansky-Kuster-Hauser syndrome), concomitant agenesis or hypoplasia
of cervix and vagina, or segmental vaginal atresia. If only one of the
mullerian ducts develops, unicornuate uterus results; rudimentary communicating
or non-communicating horn with or without functional endometrium may co-exist.
Nonfusion: Complete failure of
midline fusion results in uterus didelphys, whereas incomplete fusion leads to
bicornuate uterus
Nondegeneration: Arrest at the final
stage of degeneration or resorption of fused margins of mullerian ducts results
in uterine or longitudinal vaginal septa, or arcuate uterus. Failure of
canalization of the vaginal plate results in transverse vaginal septum.
The most widely used
method of classification of MDAs is the American Fertility Society (AFS)
classification based on the scheme of Buttram and Gibbons, which includes seven
main categories and correlates anatomic anomalies with the degree of
developmental failure. These categories are: I - segmental or complete agenesis
or hypoplasia; II - unicornuate uterus (with/without rudimentary horn); III -
didelphys uterus; IV - bicornuate uterus (complete or partial); V - septate
uterus (complete or partial); VI - arcuate uterus and VII - DES- related
abnormalities. The AFS classification is merely a framework; many MDAs coexist
and not all fit completely into the above categories. This classification has
been criticized as being awkward and confusing, as it does not account for
combinations, or for cervical and vaginal defects which remain unclassified.
Recognizing the need for
standardized common terminology among clinicians and researchers, the European
Society of Human Reproduction and Embryology (ESHRE) and European Society for
Gynaecological Endoscopy (ESGE), established a common working group named
CONUTA (CONgenital UTerine Anomalies), with the goal of developing an updated
classification system based on anatomy. Anomalies are classified separately as
uterine (U), and coexistent cervical (C) and vaginal (V), according to
increasing severity of the anatomical deviation with the normal variants at the
beginning and more deformed types at the end.
Uterine
anomalies: U0
- normal uterus; U1- dysmorphic uterus; U2 - septate uterus; U3- bicorporeal uterus; U4 - hemi-uterus; U5-
aplastic uterus; U6 – unclassified malformations. These main classes are
subdivided into anatomical varieties with clinical significance, such as
partial, complete, rudimentary horn, etc.
Cervical
anomalies: C0
– normal cervix; C1 – septate cervix; C2 – double cervix; C3 – unilateral
cervical aplasia; C4 – cervical aplasia.
Vaginal
anomalies: V0
– normal vagina; V1- longitudinal non- obstructing vaginal septum; V2 -
longitudinal obstructing vaginal septum; V3 – transverse vaginal septum and/or
imperforate hymen; V4 – vaginal aplasia.
This system was
developed using scientific research, consensus assessment and consensus
development; its clinical value however needs to be proved in day-to-day
practice.
Traditionally,
hysterosalpingography (HSG) has been used to evaluate the cervical canal,
uterine cavity and fallopian tubes; it can diagnose uterine septa, intrauterine
synechiae, submucous fibroids, as well as evaluate tubal patency. However, it
has limited accuracy as it cannot be used in virgins, it does not image
obstructed canals or the external uterine fundal contour (hence cannot
differentiate between uterus didelphys and septate uterus). Ultrasonography
alone has a variable sensitivity and specificity in diagnosis of MDAs, and
depends on the type of transducer and skill of the sonologist. Currently, MRI
is the gold standard imaging modality for MDAs because it is non-invasive, has
exceptional accuracy (96-100%), does not involve ionizing radiation, has
multiplanar capability, and allows excellent soft tissue characterization. MRI
provides for accurate classification of the type of anomaly in the pediatric
and adolescent population; it reduces the number of invasive procedures by
guiding management decisions. MRI has an excellent correlation with
intraoperative laparoscopic findings in predicting anatomical defects. Recently
the use of 3D-USG has proven to be more sensitive and specific than MRI in
categorizing specific types of MDAs, though MRI is superior for cervical and
vaginal anomalies. 3D-USG has the added advantage of being cost-effective and
providing immediate results, and as practitioners become more experienced in
its use, it may emerge as the new reference standard. Presently however there
is a lack of comparative studies between MRI and 3D-USG. MRI features of MDAs
are well described elsewhere.
Regardless of whether
diagnosis is by HSG, USG, MRI or a combination, management at a higher center
is associated with more accurate diagnosis and a reduction in the number of
inappropriate surgical interventions. After an accurate diagnosis is reached,
many treatment options exist which are usually tailored to the specific
anomaly. Vaginal atresia is surgically corrected by creation of a neovagina.
Several vaginoplasty methods have been developed and refined; the modified
McIndoe procedure remains the most common surgical approach. Various materials
used to line the neovagina are skin graft, human amnion, bowel segment, and
exogenous graft sources like artificial dermis and absorbable adhesion
barriers. Alternate methods are the Vecchietti laparoscopic procedure.
Septate uterus is the
most common MDA, and hysteroscopic septal resection is a relatively simple
procedure. However, the decision to perform septal resection should be based on
poor reproductive performance rather than the presence of a septum. Laparoscopy
has made surgical correction of MDAs less invasive, and laparoscopic
hemihysterectomy has been used successfully for the excision of a rudimentary
horn. Decision to perform metroplasty for uterus didelphys or bicornuate uterus
should be individualized, and the apparent benefits of this surgery are not
clear. Laparoscopic-assisted uterovaginal anastomosis with placement of a
silicone stent in patients with cervical agenesis along with concomitant
vaginoplasty has been described; endometriosis and subsequent hysterectomy may
be averted in these young girls and menstrual function restored. It should be
kept in mind that a high transverse vaginal septum is one of the most difficult
anomalies to treat and patients may be subjected to numerous surgical
attempts. Case reports and case series
from large centers continue to provide insights into novel surgical approaches
and operative techniques.
In conclusion, MDAs
consist of a wide range of defects, and their diagnosis and management should
be individualized taking anatomical and clinical characteristics into
consideration. Postoperative restoration of long term reproductive and sexual
function in women with MDAs continues to remain a challenge.