Summary: Patient presented for pelvic magnetic resonance imaging (MRI) after
an abnormal physical examination and a nondiagnostic transabdominal
Two endometrial cavities with normal external contour of the uterine fundus. Uterine septum extends through cervix.
Müllerian duct anomalies in women include lack of development
(hypoplasia, aplasia, or unicornuate uterus), lack of midline fusion
(didelphys or bicornuate uterus), and incomplete resorption of midline
tissue during fusion (septate and arcuate uteri). The noncomplex
anomalies which can show 2 symmetric endometrial cavities are septate,
bicornuate, and didelphys uteri. Distinction between a septate uterus
and either the didelphys or bicornuate uterus is important if
infertility warrants surgical repair.
Because the endometrial
cavities in the didelphys or bicornuate uteri are separated by normal
myometrium, a pregnancy will normally implant and be more likely to
proceed. Surgery is thus rarely performed and would entail metroplasty
via a laparotomy. The septum in a septate uterus has abnormal
vascularization and mechanics. Implantation on the septum results in
frequent spontaneous first-trimester pregnancy loss. The septum is
therefore removed; this can be done using a simpler hysteroscopic
approach. Distinguishing a didelphys or bicornuate uterus from a septate
uterus is critical.
Embryologically, 2 processes occur during
Müllerian development, lateral fusion and segmental resorption. The
paired Müllerian ducts undergo lateral fusion to form the uterus,
cervix, and upper vagina. Uterine didelphys is complete uterine
nonfusion with 2 uteri and 2 cervices separated by a normal myometrium.
In a bicornuate uterus, a normal muscular septum can extend to the
internal os (partial or bicornuate unicollis) or close to the external
os (complete or bicornuate bicollis).
Both the didelphys and
bicornuate have a deep fundal indentation (>1 cm) between 2 symmetric
horns containing endometrium. A didelphys and bicornuate uterus
represent a continuum of fusion. A didelphys and an extreme bicornuate
uterus with near complete lack of fusion may be difficult to
distinguish, but is of low importance clinically. A septate uterus has
undergone complete fusion. The external contour of the uterus is
therefore normal (Figure 1).
As lateral fusion is occurring,
septal resorption is also occurring. The intervening midline vertical
septum between the uterus, cervix, and upper vagina is resorbed
segmentally beginning in the lower uterine segment and progressing in
both directions,1 as the current case illustrates (Figure 1
and 2). The septum tends to be mainly muscular superiorly (although
histologically different from normal myometrium) and more fibrous and
thinner towards the cervix.
Septal resorption may be arrested at any point, resulting in variable lengths of septum in the septate uterus2
and infrequently in the bicornuate uterus. The myometrium in a partial
bicornuate uterus may extend to the lower uterine segment with
communication between the 2 cavities at that level (and thus defining it
as a bicornuate uterus). However, an apparent “duplicated” cervix can
result from a nonresorbed fibrous septum in the cervix.3
All entities may independently have a duplicated upper vagina.1
Upper vaginal duplication is present in 75% of didelphys uterus, but
occurs in 25% of the bicornuate and septate uteri in 25% (Figure 3) and
rarely with a normal uterus.
Because of the variable presence of a
uterine and cervical septum and a duplicated upper vagina in didelphys,
bicornuate, and septate uteri, the presence or absence of cervical or
upper vaginal duplication are not reliable in distinguishing between
them. A septate uterus with a complete septum and duplicated upper
vagina is not infrequently misdiagnosed as a didelphys uterus. Tissue
characterization by MRI is also not reliable given that the septum in
the uterine body in all entities is predominantly myometrial tissue.
Making the correct diagnosis is best made by first evaluating the
external contour of the uterus. A normal contour excludes a didelphys or
bicornuate and the uterus is either normal or septate. With the correct
anomaly now established, the presence and extent of a uterine septum
and upper vaginal duplication is independently evaluated.
symmetric Müllerian anomalies should be differentiated from the
unicornate uteri variations and the infrequent complex anomalies. A
unicornuate uterus with a communicating rudimentary horn have
asymmetrically sized horns unlike a bicornuate uterus. A didelphys
uterus with obstructed hemivagina is recognized from the simple
didelphys given its constellation of anomalies.
MRI is the most
accurate modality in characterizing the type of abnormality and is used
when other imaging studies are inconclusive. A T2-weighted acquisition
in the coronal oblique plane, parallel to the long axis of the uterus,
best shows the external contour. This case of a septate uterus shows a
normal sized uterus with a normal external contour and a duplicated
vagina. A midline septum separates 2 endometrial canals and cervices.
Some resorption had occurred at the isthmus, allowing some communication
between the lower endometrial canals.
- Troiano RN, McCarthy SM. Müllerian duct anomalies: Imaging and clinical issues. Radiology. 2004;233:19-34.
AS, Siegel CL, Moley KH, et al. Septate uterus with cervical
duplication and longitudinal vaginal septum: A report of five new cases.
Fertil Steril. 2004;81:1133-1136.
- La Fianza A, Campani
R, Villa A, et al. Communicating bicornuate uterus with double cervix
and septate vagina: An uncommon malformation diagnosed with MR imaging. Eur Radiol. 1997;7: