Diagnosis of abnormally invasive posterior placentation: the role of MR imaging

Abstract

Abnormally invasive placentation is becoming more common with a recent increase in cesarean sections and maternal age, among other risk factors. Ultrasonography is the first line-imaging, but it can be difficult to diagnose when limiting factors are present. Failure to recognize this serious placental abnormality precludes us from making the appropriate plan for the delivery and consequently can lead to fatal results. In this report, we present a case in which magnetic resonance imaging was used to diagnose posterior placenta increta missed by multiple sonographic examinations in a patient with previous myomectomies, and we also include a review of the literature on this topic. It is our conclusion that magnetic resonance imaging is superior to sonography to diagnose abnormally invasive placentation in cases of posterior placenta previa and high pretesting probability.

Keywords: Abnormal invasive placentation; Magnetic resonance imaging; Posterior placenta previa.

Fig. 1

Half-Fourier acquisition single-shot turbo spin-echo (HASTE) magnetic resonance imaging (MRI). Sagittal section depicting the posteriorly located placenta (arrow heads) covering the internal os of the cervical canal (long arrow) as well as the posterior myomectomy site (short arrow).

Fig. 2

T2-weighted axial MRI. This image depicts dark T2 bands (circled) posteriorly in the placenta (arrow).

Fig. 3

TrueFISP. Coronal image demonstrating flow within iliac vessels (arrows) and prominent periuterine vessels surrounding the lower uterine segment (circled).

Fig. 4

T1-weighted gradient echo MRI image. This image demonstrates 2 small areas of high signal periplacental hemorrhage (arrows).

Fig. 5

Transabdominal ultrasound image of the placenta. This image demonstrates a normal subplacental clear space laterally (arrows) with subtle potential loss of the clear space overlying the myomectomy site (circle).

Fig. 6

Hematoxylin and eosin stained pathology slides. These demonstrate (A) chorionic villi infiltrating into the uterine wall (arrow) at 40× magnification and (B) chorionic villi infiltrating between myometrial smooth muscle fibers (arrow) at 200× magnification.