Step 1: Understand the clinical scenario.
An infertility patient has an ultrasound suggesting a uterine anomaly. The question asks for the best investigation to confirm the diagnosis -- implying both confirmatory diagnosis and ideally therapeutic potential.
Step 2: Role of each investigation.
Transvaginal sonography (TVS) is a good screening tool but has limited ability to fully characterise uterine anomalies such as septate vs bicornuate uterus. HSG can outline the internal uterine cavity and tubal patency but cannot visualise the external uterine contour or peritoneal cavity.
Step 3: Why Hysteroscopy + Laparoscopy is best.
Combined hysteroscopy and laparoscopy is the gold standard for evaluating uterine anomalies in infertility. Hysteroscopy visualises the internal uterine cavity (detects septa, polyps, submucosal fibroids, synechiae) while laparoscopy simultaneously visualises the external uterine contour (distinguishes septate from bicornuate uterus) and evaluates the peritoneal cavity, fallopian tubes, and ovaries. Importantly, this combined approach is both diagnostic AND therapeutic at the same sitting -- a uterine septum can be resected hysteroscopically while laparoscopy is ongoing.
Conclusion: Hysteroscopy combined with laparoscopy is the best investigation to confirm uterine anomalies in infertility patients.