Advances in image-scanning technology have led to vast improvements in medicine, especially in the diagnosis of fetal anomalies and placenta evaluation. In general, two main technologies are used to obtain images within the uterus during pregnancy ñ ultrasound (US) and magnetic resonance imaging (MRI). US examination is the primary method of gravid uterus assessment because it is patient-friendly, effective, cost-efficient and considered to be safe. MRI is generally used when US cannot provide sufficiently high-quality images. It offers high-resolution fetal and placenta imaging with excellent contrast that allows visualization of internal tissues. Placenta percreta is the most feared form of abnormally adherent placenta. Its incidence has increased because of high cesarean section rates.
The main imaging findings in abnormally adherent placenta are:
ï Loss of the ìclear zoneî or irregularity of the hypoechoic plane in the myometrium underneath the placental bed.
ïAbnormal placental lacunae. Presence of numerous lacunae including some that are large and irregular often containing turbulent flow.
ï Bladder wall interruption.
ï Placental bulge. Deviation of the uterine serosa away from the expected plane. The uterine serosa appears intact, but the outline shape is distorted.
ï Focal exophytic mass. Placental tissue seen breaking through the uterine serosa and extending beyond it.
ï Color Doppler imaging shows uterovesical hypervascularity.
ï Bridging vessels appearing to extend from the placenta across the myometrium and beyond the serosa into the bladder or other organs. Often running perpendicular to the myometrium.
The key concern of this talk will be:
ï The risk of placenta accreta increases according the number of Cesarean-section.
ï Placenta accreta is mostly associated with placenta previa.
ï The most sensitive US finding for placenta accreta is the presence of placenta lacunae, that can also be observed in MRI.
ï MRI may aid in diagnosis by demonstrating increased intraplacental vascularity, fibrin band of dark T2 signal and direct placental invasion of adjacent structures.