USS criteria of placenta accreta

Question 1

Greyscale features

Answer 1

• Loss of the retroplacental sonolucent zone
• Irregular retroplacental sonolucent zone
• Thinning or disruption of the hyperechoic serosa–bladder interface
• Presence of focal exophytic masses invading the urinary bladder
• Abnormal placental lacunae.

Question 2

Colour Doppler features

Answer 2

• Diffuse or focal lacunar flow
• Vascular lakes with turbulent flow (peak systolic velocity over 15 cm/s)
• Hypervascularity of serosa–bladder interface
• Markedly dilated vessels over peripheral subplacental zone.

Question 3

Three-dimensional power Doppler features

Answer 3

• Numerous coherent vessels involving the whole uterine serosa–bladder junction (basal view)
• Hypervascularity (lateral view)
• Inseparable cotyledonal and intervillous circulations, chaotic branching, detour vessels (lateral view)

Question 4

Main MRI features of placenta accreta

Answer 4

• Uterine bulging
• Heterogeneous signal intensity within the placenta
• Dark intraplacental bands on T2-weighted imaging.