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Copyright 2009 Section Name “The follicular phase starts on the first day of menses until ovulation (day 14 of a 28-day cycle). By days 5–7, follicles may be seen sonographically as small, well-defined, cystlike structures (4). By days 8–12, the dominant follicle, which typically produces the ovum, is evident due to its larger size (>14 mm) (5). All follicles are generally distributed randomly between both ovaries (Fig 1). In 5%–11% of cycles, two dominant follicles may develop but not within the same ovary(5). “ “During ovulation, the dominant follicle ruptures, releasing the ovum and fluid and causing an abrupt decrease in follicular size. Sonographically, this fluid may be detected in the cul-de-sac in up to 40% of patients (6). “ “The luteal phase follows ovulation and lasts until menses begins, typically 14 days. Initially, a corpus hemorrhagicum develops from the remnant dominant follicle, which is visualized sonographically as an irregular cyst with scalloped margins. The walls become highly vascularized, forming a corpus luteum, which can be seen as a small, thick-walled, solid-appearing structure with internal echoes and a circumferential “ring of fire” at color Doppler sonography (7). “ |
