Placenta lakes vs lacunae: spot the differences.

Sonographic sonolucencies are anechoic areas surrounded by tissue of normal echogenicity commonly found in the placental parenchyma during the second and their trimesters of pregnancy. The ultrasound images of lakes and lacunae are generated by the low echogenicity of villous free areas within the placental parenchyma, filled with maternal blood of varying velocities. In normal placentation, lakes usually start appearing as soon as maternal blood starts flowing freely inside the intervillous space at the end of the first trimester whereas in accreta placentation lacunae develop progressively during the second trimester. Larger lakes are mainly found in area that have physiologically less villous tissue under the fetal plate or at both placental edges. Lakes can also be found in the centre of a lobule above the entry of a spiral artery and these lakes can transform into echogenic cystic lesion which have been associated with poor fetal growth. Lacunae are formed by the distortion of one or more placental lobule developing inside a uterine scar and are the consequence of high volume, high velocity flows from the radial/arcuate arteries and are associated with a high probability of PAS at birth. They often present with ultrasound signs of uterine remodelling following scarification. Lakes and lacunae can co-exist in the same placenta and both will change in size and shape as pregnancy advances. The ultrasound images of lakes and lacunae are generated by the low echogenicity of villous free areas within the placental parenchyma, filled with maternal blood of varying velocities. Lakes of different sizes, positions and shapes are not of any clinical significance. There is a weak association between cystic lesions and placental malperfusion. By contrast, lacunae are secondary to the development of one or more placental lobules inside a uterine scar and are the main ultrasound marker of accreta placentation. Better understanding of the etiopathology of the development of placental sonolucent spaces and other associated morphological changes is necessary to identify patients at risk of subsequent complications during pregnancy and/or at delivery. This article is protected by copyright. All rights reserved.