The MRI features of placental adhesion disorder – a pictorial review

Placental adhesion disorder (PAD) comprises placenta accreta, increta and percreta lesions, these are classified according to the depth of uterine invasion. Although PAD is considered a rare condition, its incidence has increased 10 fold in the last 50 years. Ultrasound is the primary imaging modality for assessment of the placenta, and in the majority of cases it is sufficient for diagnosis, however when ultrasound findings are suspicious or inconclusive, MRI is recommended as an adjunct imaging technique. Numerous MRI features of PAD have been described, including dark intra-placental bands, disorganised intra-placental vascularity and abnormal uterine bulging. This pictorial review describes and illustrates these characteristics and discusses their implications in planning delivery. In addition we present a series of ‘pitfall’ cases to aid the interpreting radiologist and discuss management of PAD. PAD is a clinical and diagnostic challenge that is encountered with increasing frequency requiring a cohesive multidisciplinary approach to its management.