G39. Malformations of the Genital Tract

I. Basic Concepts

Embryologic Origin

• Mullerian / paramesonephric ducts: fallopian tubes, uterus, cervix and upper vagina.
• Urogenital sinus: vestibule and lower vagina.
• Normal uterine development: duct formation → medial migration/fusion → septum resorption → normal uterine cavity.
• Main mechanisms: formation failure, incomplete fusion or incomplete septum resorption.
• Associated renal tract anomalies are important because genital and urinary development are linked.

Clinical Presentation

• May be asymptomatic and found during infertility work-up, pregnancy care, ultrasound, hysteroscopy or surgery.
• Symptoms: primary amenorrhea, cyclic pelvic pain, dysmenorrhea, dyspareunia, infertility, recurrent miscarriage.
• Obstructive anomalies: menstrual blood cannot exit → hematocolpos/hematometra → cyclic pain, pelvic mass.
• Pregnancy risks: miscarriage, malpresentation, preterm birth, fetal growth restriction and cesarean delivery.

II. Mullerian / Uterine Anomalies

Main Types

1. Agenesis/hypoplasia: absent or rudimentary uterus/cervix/upper vagina.
2. Unicornuate uterus: unilateral formation failure of one Mullerian duct.
3. Uterus didelphys: complete failure of fusion → two uterine bodies, usually two cervices; may have longitudinal vaginal septum.
4. Bicornuate uterus: partial fusion failure → two uterine horns, heart-shaped external fundal contour.
5. Septate uterus: normal external uterine contour but incomplete resorption of midline septum.
6. Arcuate uterus: mild fundal indentation; usually small clinical significance.

Septate Uterus

• Mechanism: incomplete resorption of the fused Mullerian midline septum.
• Anatomy: normal/near-normal external uterine contour + internal septum dividing cavity.
• Clinical importance: reduced fertility, recurrent early miscarriage and pregnancy loss.
• Diagnosis: 3D ultrasound or MRI; hysteroscopy defines cavity but laparoscopy/3D imaging helps distinguish from bicornuate uterus.
• Treatment: hysteroscopic septoplasty/metroplasty when symptomatic, recurrent pregnancy loss or infertility context.

Bicornuate Uterus

• Mechanism: incomplete fusion of Mullerian ducts.
• Anatomy: two uterine cavities/horns with external fundal cleft; heart-shaped uterus.
• Clinical importance: miscarriage, malpresentation, preterm birth and complicated pregnancy.
• Treatment: usually expectant; surgical metroplasty only rarely.

Uterus Didelphys

• Mechanism: complete failure of Mullerian duct fusion.
• Anatomy: two separate uterine bodies, usually two cervices; often longitudinal vaginal septum.
• Pregnancy may be possible but risks include miscarriage, preterm birth and malpresentation.
• Obstructed hemivagina: cyclic pain + hematocolpos on one side; often associated with ipsilateral renal agenesis.
• Treatment: resect obstructing vaginal septum if present; otherwise usually conservative pregnancy surveillance.

Unicornuate Uterus

• Mechanism: unilateral failure of Mullerian duct formation.
• Anatomy: one small uterine horn; may have rudimentary horn.
• Clinical importance: infertility, miscarriage, preterm birth, malpresentation and fetal growth restriction.
• Functional rudimentary horn: cyclic pain/hematometra; pregnancy in rudimentary horn can rupture.
• Treatment: excision of functional rudimentary horn when symptomatic or pregnancy risk is present.

III. Cervical and Vaginal Anomalies

Cervical Anomalies

• Cause: Mullerian malfusion or canalization disorder.
• Types: duplicated cervix, septate cervix, cervical agenesis/atresia.
• Clinical significance: infertility, recurrent pregnancy loss, dysmenorrhea or obstructed menstrual flow.
• Management depends on anatomy, symptoms, fertility wish and obstruction.

Imperforate Hymen

• Definition: hymenal membrane without opening.
• Presentation at puberty: primary amenorrhea + cyclic pelvic pain.
• Findings: bulging bluish hymen; hematocolpos may feel like a pelvic/perirectal mass.
• Complications: hematocolpos, hematometra, urinary retention and endometriosis from retrograde menstruation.
• Treatment: cruciate incision/excision of obstructing hymenal tissue with drainage.

Transverse Vaginal Septum

• Mechanism: failed fusion/canalization between Mullerian-derived upper vagina and urogenital sinus-derived lower vagina.
• Upper reproductive tract: usually normal.
• Presentation: primary amenorrhea, cyclic pelvic pain, hematocolpos/hematometra if complete obstruction.
• Treatment: surgical excision of septum; complex/high septa need specialist repair.

Longitudinal Vaginal Septum

• Often associated with uterus didelphys or septate uterus.
• Symptoms: dyspareunia, tampon difficulty, obstructed hemivagina or dysmenorrhea.
• Treatment: excision if symptomatic or obstructing.

IV. Vaginal Agenesis and Vulvar Anomalies

Vaginal Agenesis / Mullerian Agenesis

• Mullerian agenesis / Mayer-Rokitansky-Kuster-Hauser syndrome: absent/hypoplastic uterus, cervix and upper vagina with normal ovaries.
• Karyotype: 46,XX.
• Clinical features: primary amenorrhea, normal secondary sexual characteristics, normal external genitalia, short/blind vagina.
• Associated anomalies: renal and skeletal anomalies may occur → renal imaging.
• Treatment: counseling; progressive vaginal dilatation first-line; surgery if dilatation fails or is unacceptable.
• Fertility: ovarian function present; genetic child possible with assisted reproduction + gestational carrier where legal.

Vulvar / External Genital Anomalies

• Clinically important vulvar anomaly: ambiguous genitalia.
• Ambiguous genitalia at birth: urgent structured evaluation before sex assignment.
• Important causes: congenital adrenal hyperplasia, androgen insensitivity, gonadal dysgenesis and other DSDs.
• See also: primary amenorrhea and anomalies of sexual differentiation.

V. Diagnosis and Management Principles

Diagnosis

• History: menarche, cyclic pain, dysmenorrhea, dyspareunia, tampon difficulty, infertility, miscarriage/preterm birth history.
• Physical exam: external genitalia, hymen, vaginal length/patency, septum, cervix number/position.
• Ultrasound: first-line imaging; 3D ultrasound useful for uterine cavity and fundal contour.
• MRI: best for complex Mullerian/vaginal anatomy and surgical planning.
• Hysteroscopy: evaluates/treats intrauterine septum; renal imaging is important when Mullerian anomaly is diagnosed.

Treatment Principles

• Asymptomatic non-obstructive anomaly: often observation and counseling.
• Obstructive anomaly: relieve obstruction to prevent pain, infection, endometriosis and fertility damage.
• Septate uterus with reproductive problems: hysteroscopic septoplasty.
• Pregnancy with uterine anomaly: high-risk obstetric follow-up for miscarriage, malpresentation and preterm birth.
• Surgery should be anatomy-specific; avoid unnecessary correction of incidental variants.