Normal Ovary — Luteal Phase

During the luteal phase (post-ovulation, Day ~14–28), the ovary is dominated by the corpus luteum (CL), a physiologic structure formed from the ruptured follicle. It produces progesterone to support potential implantation. Sonographically, its characteristic appearance allows confident identification of a normal luteal-phase ovary and avoids misinterpretation as pathology.

Key sonographic features — normal luteal-phase ovary:

• Corpus luteum (CL)
• Internal contents may be hypoechoic, mixed echogenicity, or lace-like (hemorrhagic variant)
• Characteristic peripheral ring of the luteal wall
• Doppler showing the “ring of fire”: well-vascularized peripheral flow with low resistance (RI 0.4–0.5)
• Normal ovarian volume (~5–15 mL), possibly mildly enlarged due to CL
• Ovarian stroma mildly echogenic; small background follicles may still be present
• Possible minimal physiologic free fluid in the pouch of Douglas, especially immediately post-ovulation

Physiology review: The luteal phase is characterized by:

• Progesterone peak 6–8 days after ovulation
• Moderate estrogen increase
• Negative feedback on LH and FSH

The sonographic appearance of the CL directly reflects its role as a temporary endocrine gland.

Differentiation from pathology:

• Vs. simple ovarian cyst: CL has a thick vascular wall; cysts are thin-walled and anechoic.
• Vs. ectopic pregnancy: CL is within the ovary; ectopic tubal rings are separate from the ovary.
• Vs. ovarian torsion: normal CL shows preserved low-resistance flow; torsion shows enlarged ovary with reduced/absent venous flow.

Clinical significance: This appearance confirms recent ovulation and is a normal cyclic finding. Radiology reports frequently describe:

• “Normal ovary—luteal phase appearance”
• “Corpus luteum present”
• “No adnexal mass”

If pregnancy occurs, the CL persists as the corpus luteum graviditatis until approximately 10–12 weeks.

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Suggested caption for readers: In the luteal phase, the ovary normally contains a corpus luteum, often thick-walled and vascular (“ring of fire”). This is a physiologic cyclic structure and should not be confused with a pathologic ovarian cyst or adnexal mass when typical features are present.