A 32-year-old woman presents with primary infertility of 3 years' duration. Menarche at age 13, regular cycles of 28 days, and no dysmenorrhea. General examination and pelvic examination are normal. Husband's semen analysis is normal. Which is the most appropriate next investigation to evaluate tubal patency and exclude anatomical abnormalities?

## Investigation of Choice for Tubal Patency Assessment ### Clinical Context In a woman with regular ovulatory cycles, normal pelvic examination, and normal male factor, the next step is to assess tubal patency and uterine cavity anatomy. This is a first-line structural assessment. ### Why HSG is the Gold Standard **High-Yield:** HSG is the **investigation of choice** for initial assessment of tubal patency and uterine cavity abnormalities in infertility workup [cite:Park 26e Ch 8]. **Key Point:** HSG is: - Non-invasive, office-based procedure - Cost-effective and widely available - Provides both tubal patency status (spillage into peritoneal cavity) AND uterine cavity morphology - Can detect proximal tubal occlusion, distal occlusion, hydrosalpinx, and intrauterine pathology (polyps, fibroids, septate uterus) - Therapeutic benefit: oil-based contrast may improve fertility in some cases (Heyer-Cederquist effect) ### Timing & Technique - Performed in **follicular phase** (days 7–10 of cycle) to avoid pregnancy and allow optimal visualization - Water-soluble or oil-based contrast used under fluoroscopy - Spillage of contrast into peritoneal cavity confirms tubal patency ### Comparison with Other Modalities | Investigation | Indication | Advantage | Limitation | |---|---|---|---| | **HSG** | First-line tubal assessment | Non-invasive, evaluates both tubes & cavity | Cannot assess ovarian reserve, endometriosis, or adhesions | | **Diagnostic laparoscopy** | Suspected endometriosis, adhesions, or HSG abnormality | Gold standard for visualizing pelvis; therapeutic | Invasive, requires anesthesia; reserved for selected cases | | **Transvaginal ultrasound** | Uterine pathology, ovarian reserve | Non-invasive, no radiation | Poor sensitivity for tubal patency | | **MRI pelvis** | Detailed uterine anatomy (e.g., Müllerian anomalies) | Excellent soft-tissue resolution | Expensive, not first-line; radiation-free but time-consuming | **Clinical Pearl:** If HSG shows tubal occlusion or suspected endometriosis, diagnostic laparoscopy with chromopertubation is the next step for confirmation and therapeutic intervention.