HYPOECHOIC OR CYSTIC LESIONS OF THE PLACENTA

ULTRASOUND

Cystic or hypoechoic areas in the placenta are the most frequent abnormality detected sonographically.

• Most commonly seen after 25 weeks menstrual age.
• Represent a wide variety of placental abnormalities.
• Usually of no clinical significance.
• The more mature the placenta the more frequent and numerous are the hypoechoic areas.
• Concern should arise if (1):
1. They appear prior to 20-25 weeks.
2. More numerous than expected (expect £3-4 hypoechoic areas).
3. They are larger than normal (normally £2 cm).

DIFFERENTIAL DIAGNOSIS

1. Maternal lakes - avillous spaces.
2. True placental cysts (cytotrophoblastic or decidual septal cysts).
3. Allantoic duct cysts (at placental attachment).
4. Subchorionic / retroplacental hematoma.
5. Subamniotic hematomas.
6. Circumvallate placenta (sonolucent subamniotic cysts).
7. Vanishing twin may present as a cystic mass adjacent to placenta.

REFERENCES

1. Harris RD, Cho C, Wells WA. Sonography of the placenta with emphasis on pathological correlation. Seminars in Ultrasound, CT, and MRI 1996;17(1):66-89.