Corpus luteum cyst is a functional cystic lesion developing from excessive growth of the corpus luteum after ovulation with fluid/blood accumulation. Common in premenopausal women, typically seen during the luteal phase (second half of cycle) or early pregnancy. The most characteristic ultrasound finding is a thick, crenulated (scalloped) wall with intense peripheral vascularity on Doppler (ring of fire pattern). Contents are usually hemorrhagic. The vast majority show spontaneous regression within 1-3 menstrual cycles.
Age Range
15-45
Peak Age
25
Gender
Female predominant
Prevalence
Very Common
After ovulation, the follicle collapses forming the corpus luteum. Luteinized granulosa and theca cells secrete progesterone and develop intense neovascularization — this new vascular network is the anatomic basis of the ring of fire pattern on Doppler. Normal corpus luteum can grow up to 3 cm; beyond this it is defined as a cyst. Hemorrhage into the cyst is common due to capillary fragility in the neovascularization — therefore contents are usually hemorrhagic, showing internal echoes or reticular pattern on ultrasound. The cyst wall consists of luteinized cells and is rich in vascular structures — reflected as thick (3-8 mm), crenulated wall on ultrasound. Without pregnancy, hCG drops, corpus luteum degenerates, and the cyst begins to shrink within 14 days. In pregnancy, it may persist until 10-12 weeks with hCG support.
Intense, circumferential (complete ring-shaped) vascularity around the cyst wall on color Doppler ultrasound is the signature finding of corpus luteum cyst. This pattern reflects intense neovascularization induced by luteinized cells via VEGF after ovulation. Low resistance index (RI <0.4-0.5) supports active luteal function. Ring of fire pattern can also be seen in ectopic pregnancy — clinical correlation with β-hCG level is always necessary.
Intense, circumferential (ring-shaped) vascularity around the cyst wall on color Doppler. Low-resistance arterial flow pattern. Described as 'ring of fire.'
Report Sentence
Intense circumferential vascularity (ring of fire pattern) is observed around the cyst wall on color Doppler, consistent with a corpus luteum cyst.
3-8 mm thick wall with irregular (crenulated/scalloped) inner contour. Wall shows echogenicity varying between hypoechoic and isoechoic. Outer contour is usually smooth.
Report Sentence
The cyst wall is thick (___ mm) with crenulated (scalloped) inner contour, consistent with a corpus luteum cyst.
Low-to-medium level internal echoes, reticular pattern, or fluid-fluid level within the cyst. Content is hemorrhagic in character. May be completely anechoic but usually contains echogenic component.
Report Sentence
Low-level internal echoes/reticular pattern are observed within the cyst, consistent with hemorrhagic content.
Hyperintense signal on T1-weighted sequences — hemorrhagic content (methemoglobin). Signal may be homogeneous or heterogeneous. Wall shows marked enhancement.
Report Sentence
The lesion shows hyperintense signal on T1-weighted sequences, consistent with hemorrhagic corpus luteum cyst. Marked enhancement is observed in the wall.
Cystic lesion surrounded by thick, intensely enhancing wall on CT. Content density may be increased if hemorrhagic (30-60 HU). Wall enhancement is prominent in arterial phase.
Report Sentence
A thick-walled cystic lesion with intensely enhancing wall is seen in the adnexal region, consistent with a corpus luteum cyst.
Criteria
Anechoic or low-echogenicity content, no significant hemorrhage. Thick crenulated wall and ring of fire pattern present.
Distinct Features
Content is clear fluid, hemorrhage is minimal. Ring of fire pattern and thick wall are diagnostic. Differentiated from simple cyst by thick wall and vascularity.
Criteria
Significant hemorrhagic content within cyst: internal echoes, reticular pattern, retracting clot, or fluid-fluid level. Ring of fire pattern preserved.
Distinct Features
Most common subtype. Thick crenulated wall and ring of fire pattern in addition to hemorrhagic cyst findings confirm diagnosis. T1 hyperintense signal on MRI is evidence of hemorrhage. May present with acute pelvic pain.
Criteria
Corpus luteum cyst persisting with β-hCG support in early pregnancy (first trimester). May persist until 10-12 weeks, then regresses when placenta takes over progesterone production.
Distinct Features
Corpus luteum cyst in pregnancy may be confused with ectopic pregnancy — β-hCG trend and presence of intrauterine gestational sac are differentiating. Cyst shrinks as pregnancy progresses. Torsion risk is increased.
Distinguishing Feature
Simple cyst has thin (<3 mm), smooth wall and is avascular on Doppler — no ring of fire pattern. Corpus luteum cyst has thick (3-8 mm), crenulated wall with intense peripheral vascularity.
Distinguishing Feature
Hemorrhagic cyst has thin wall and shows minimal vascularity on Doppler. Corpus luteum cyst shows thick crenulated wall and ring of fire pattern. Both may contain hemorrhagic content but wall characteristics and vascularity distinction is definitive.
Distinguishing Feature
Tubo-ovarian abscess is a thick, irregular-walled cystic lesion with heterogeneous content. May show peripheral vascularity but more irregular than ring of fire pattern. Fever, leukocytosis, and pelvic inflammatory disease findings accompany. Corpus luteum cyst has no infection findings.
Urgency
surveillanceManagement
conservativeBiopsy
Not NeededFollow-up
6-monthCorpus luteum cyst is a benign functional lesion and the vast majority show spontaneous regression within 1-3 menstrual cycles. Follow-up US at 6-8 weeks from initial diagnosis is recommended. If detected in pregnancy, no need to panic — may persist until 10-12 weeks and shrinks when placental function begins. Complications include cyst rupture (hemoperitoneum — acute abdomen), torsion (especially in cysts >5 cm), and ongoing bleeding. Emergency surgical intervention may be needed with rupture or torsion findings. Corpus luteum cyst is not expected in postmenopausal women — neoplasia should be excluded in this setting.
Corpus luteum cyst is a physiological structure and does not require treatment. May cause acute pelvic pain with spontaneous hemorrhage. Risk of hemoperitoneum in case of rupture. Beta-hCG test is important to differentiate from ectopic pregnancy.