Role of MRI in assessment of Placental Invasion

Abstract

PA is a significant cause of maternal morbidity and mortality and is now the most common reason for emergent postpartum hysterectomy. Placenta previa and previous cesarean section are the two most important known risk factors for PA. Accurate prenatal identification of affected pregnancies allows optimal obstetric management. Ultrasonography (US) remains the primary diagnostic tool, and routine US examination at 18–20 weeks gestation affords an ideal opportunity to screen for the disorder. This modality has enjoyed great popularity because it is widely available, patient friendly, and relatively inexpensive. However, US is operator-dependent, limited by large body habitus, posterior placenta and the findings may not reliably differentiate between the degrees of myometrium invasion. In recent years, there has been increased interest in magnetic resonance (MR) imaging for the evaluation of PA, since it can provide excellent soft tissue resolution and information on depth of invasion and more clearly depict posterior placentas. It can be used as complementary imaging modality and problem solving method especially with equivocal ultrasound or Doppler examination and when further characterization is require. MRI can rule out or confirm the diagnosis, for example, the presence of parametrial invasion in cases of placental adherence which results in modifications of surgical techniques, allowing a reduction in historical morbidity and a significant increase in conservative surgeries. MRI is an excellent diagnostic modality in gravid patients with high risk for PAD, and practitioners should be aware of this condition and its imaging features, ultimately change surgical management. PA is a clinical and diagnostic challenge that is being encountered with increasing frequency. Clinicians should be aware of the clinical issues, risk factors, and imaging findings associated with PA to facilitate optimal case management.