Understanding Normal Ovaries on Ultrasound

A baseline ultrasound of the ovaries is a critical step in assessing a woman’s reproductive health. It helps us evaluate the ovarian reserve, track the menstrual cycle, and screen for abnormalities. Here is what we look for in a normal, healthy ovary during a scan.

1. Anatomy and Volume

The ovaries are oval-shaped structures located on either side of the uterus within the ovarian fossa.

• Mean Volume: Approximately 4.9 ml is considered normal.
• Position: They usually lie near the internal iliac artery and vein, though their position can vary.

2. Antral Follicle Count (AFC)

The best time to evaluate the ovaries is on Day 2 or Day 3 of the menstrual cycle (Follicular Phase). During this time, we measure Antral follicles (small sacs containing immature eggs) ranging from 2-9 mm.

3. Ovulation and Color Doppler

In a natural cycle, one follicle becomes “dominant,” reaching a size of 17–24 mm before releasing the egg (ovum).

• Blood Flow: Normal stromal blood flow velocity is 6–12 cm/sec. Flow velocity typically increases just before and immediately after ovulation.
• Corpus Luteum: After the egg is released, the follicle transforms into the Corpus Luteum. On ultrasound, it appears as a round cystic mass with thick, echogenic walls.
• The “Ring of Fire”: On Power Doppler, the Corpus Luteum displays a characteristic “Ring of Fire” appearance due to highly increased blood flow around it.