Metroplasty

Definition

Causes / Indications (Why Metroplasty is Needed)

Embryological Basis

• Complete septate uterus: septum extends from fundus through the cervix to the vagina
• Incomplete (partial) septate uterus: septum extends from the fundus into the cavity but does not reach the cervix

Classification (American Fertility Society / Buttram & Gibbons)

Clinical Consequences Driving Indication

• Recurrent pregnancy loss (RPL): The septum has the worst obstetric outcome of all Müllerian abnormalities. Septate uterus is found in 5-10% of women with early pregnancy loss, and up to 25% with second/third trimester losses (Berek & Novak's Gynecology, p. 2063)
• Infertility: Some evidence that metroplasty improves fecundity (though less robust than RPL data)
• Preterm labour and malpresentation (breech, transverse)
• Placental abruption and intrauterine growth restriction
• Previous IVF failure: Hysteroscopic identification and treatment of missed anomalies improves pregnancy rates

Investigations

1. Hysterosalpingography (HSG)

• Generally the best initial imaging step in infertile women as it also assesses tubal patency
• Shows the intracavitary defect but cannot reliably distinguish septate from bicornuate uterus
• Sensitivity ~44% for uterine malformations alone

2. Transvaginal Ultrasound (2D TVS)

• 75% PPV for intracavitary polyps; 44% sensitivity for uterine malformations
• Insufficient alone to characterise septate uterus

3. Saline Infusion Sonography / Sonohysterography (SIS)

• Transcervical saline instillation during TVS to distend the cavity
• 77.8% sensitivity for congenital anomalies - better than 2D TVS or HSG
• When combined with 3D technology, SIS is particularly good at assessing overall uterine contour and delineating septate uteri
• Well tolerated; also assesses adnexa and myometrium

4. Three-Dimensional Ultrasound (3D TVS)

• Emerging modality of choice for imaging Müllerian anomalies - noninvasive, reliable, high concordance with MRI
• Can differentiate septate from bicornuate uterus by assessment of the external fundal contour

5. MRI (Gold Standard)

• Gold standard for imaging congenital uterine anomalies (Berek & Novak's Gynecology, p. 2063)
• Particularly useful for:
  • Differentiating septate (convex/flat external contour) from bicornuate uterus (concave fundus with ≥1 cm cleft)
  • Diagnosing rudimentary uterine horns
  • Assessing septum dimensions (length, thickness) for surgical planning
• Coronal oblique T2-weighted images are the key sequence
• Used when 3D ultrasound is not available or inconclusive

6. Hysteroscopy

• Diagnostic and therapeutic: directly visualises the intracavitary septum
• Can be performed in an office setting under local anaesthesia
• Mandatory when radiologic images are suspicious or inconclusive
• Also allows "see and treat" in the same setting

7. Laparoscopy (when combined with hysteroscopy)

• Allows simultaneous inspection of the external uterine contour to confirm septate (vs. bicornuate) uterus
• Provides guidance during hysteroscopic resection to reduce perforation risk

Additional Investigations

• Renal tract imaging (ultrasound or IVP): mandatory when any Müllerian anomaly is confirmed, due to proximity of paramesonephric and urinary systems during development
• Karyotype if indicated (recurrent pregnancy loss workup)
• Endometrial biopsy if chronic endometritis is suspected

Management

Conservative (Expectant)

• Not all septate uteri require treatment. Indications for surgery include:
  • RPL (≥2 losses) associated with a septate uterus
  • Infertility with no other cause found
  • Poor obstetric outcomes (preterm birth, malpresentation)
• 59.5% of women with septate uterus achieve a successful pregnancy without intervention (vs. 71.7% with a normal uterus) - Creasy & Resnik's Maternal-Fetal Medicine, p. 982

Surgical: Hysteroscopic Metroplasty (Method of Choice)

Preoperative Preparation

• Timing: follicular phase of the cycle (thinner endometrium aids visualisation)
• Can be performed under general anaesthesia (operating room) or local anaesthesia (office-based)
• Laparoscopic guidance is often used, especially for complete septa, to prevent uterine perforation

Technique

1. The uterine cavity is distended with fluid medium (normal saline for bipolar; glycine/sorbitol for monopolar)
2. The septum is visualised stretching between the two cavities
3. Septal transection proceeds from the inferior apex of the septum toward the fundus, using:
   • Mechanical scissors (preferred for vascular-poor septa - minimal thermal risk)
   • Electrosurgical needle, knife, or bipolar loop (monopolar and bipolar instrumentation with minimal thermal injury when properly applied)
4. End-point of resection: attainment of two of three criteria - pain, bleeding, or visualisation of myometrial fibres ("see and treat" office protocol)
5. Laparoscopic transillumination helps ensure the fundal myometrium is not violated

Office-Based "See and Treat" Protocol

• Local anaesthesia: ½% lidocaine with 1:200,000 epinephrine injected into the septum or each cornu (to capture T10 innervation alongside the utero-ovarian ligament)
• No systemic narcotics required in most cases

Post-operative Management

• IUD or oestrogen therapy (e.g., conjugated oestrogens 1.25 mg/day for 30-60 days) may be prescribed post-resection to reduce intrauterine adhesion formation - though this practice varies
• Follow-up hysteroscopy or SIS at 6-12 weeks to assess cavity and detect adhesions or residual septum
• Pregnancy can typically be attempted after 1-2 normal menstrual cycles

Outcomes and Evidence

• Live birth rates in septate uterus: 81.3% with surgery vs. 61.5% without surgery (Creasy & Resnik's, p. 982)
• Hysteroscopic metroplasty significantly reduces pregnancy loss rates, but the effect on infertility per se is less clear (Berek & Novak's, p. 2064)
• A 2017 Cochrane review found no randomised trials of metroplasty vs. expectant management in RPL with septate uterus - high-quality RCT evidence is lacking
• ASRM guidelines: limited support for hysteroscopic septum resection to decrease subsequent losses in women with RPL

Complications of Hysteroscopic Metroplasty

• Uterine perforation (reduced by simultaneous laparoscopy or US guidance)
• Fluid overload / dilutional hyponatraemia (monitoring of fluid deficit required)
• Intrauterine adhesions (Asherman syndrome)
• Incomplete resection (residual septum - may require repeat procedure)
• Failure to improve reproductive outcomes in some patients

When Abdominal Metroplasty is Still Used

• Severely bicornuate uteri (requiring unification rather than simple septal resection)
• When laparoscopic/hysteroscopic approaches are not feasible

• Berek & Novak's Gynecology, pp. 1361, 2063-2064
• Creasy & Resnik's Maternal-Fetal Medicine, pp. 981-982
• Grainger & Allison's Diagnostic Radiology, p. 890