Magnetic resonance imaging in 300 cases of placenta accreta: surgical correlation of new findings

Background.  To establish the usefulness of placental magnetic resonance in patients with a diagnosis of placenta accreta through the correlation of diagnostic images and surgical findings. Methods.  Three hundred patients with ultrasound signs of placenta accreta were studied. In 252 patients, magnetic resonance imaging (MRI) was performed in a closed 1.5 T-resonator, and in 48 patients, open 0.23 T-set was used. T1 and T2 slices in the three planes were performed, and placental invasion was classified in depth levels and topographic areas in relation to the posterior vesical wall. The final degree of invasion was established during surgery according to clinical and anatomical criteria. The information obtained with MRI was analyzed, thus establishing its relevance to the change in surgical technique. Results.  In 286 cases, MRI provided topographic information of placental invasion, and in 90 patients, it modified invasion levels. Undiagnosed parametrium extent was determined in 11 cases, and 11 other cases were reclassified as placenta previa. Changes in conduct following MRI study included: recommendation to modify surgery date at week 35, recommendation for prophylactic ureteral catheterization, recommendation for the use of intraoperative blood salvage, possibility of approach through Pfannenstiel incision, probability of segmental myometrial approach, probability of aortic clamping, need to investigate subclinical disseminated intravascular coagulation, need of posterior pelvic dissection, and the possibility of uterine conservation. Conclusions.  Magnetic resonance imaging turned out to be essential to define the topography and area of placental invasion. New findings modified surgical tactic and technique, allowing a reduction in historical morbidity and a significant increase in conservative surgeries.