What is the best initial imaging test when evaluating suspected endometriosis?

• A. Bimanual exam
• B. Pelvic ultrasound
• C. Laparotomy + biopsy
• D. Clinical diagnosis

Answer: (B)

When evaluating suspected endometriosis, the first imaging step is pelvic ultrasound because it is noninvasive, readily available, and cost-effective. It can reliably detect ovarian endometriomas and other pelvic pathology that can mimic or accompany endometriosis, helping to guide management and rule out alternative causes of pelvic pain. However, ultrasound has limitations in detecting tiny peritoneal implants, so it does not provide a definitive diagnosis in most cases. The definitive diagnosis is made by laparoscopy with direct visualization and biopsy, which is reserved for cases where imaging and symptoms persist or when surgical treatment is planned. MRI can be useful for characterizing deep infiltrating disease when ultrasound findings are inconclusive or for preoperative planning. Physical examination like a bimanual exam can raise suspicion but is not an imaging test, and a clinical diagnosis alone is not sufficient when imaging can help clarify the situation.