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Placenta Accreta

Case Detail

Anatomy: Genitourinary
Joseph Junewick, MD FACR
Diagnostic Category: Neoplasia Benign
Created: about 1 year ago
Updated: about 1 year ago
Tags: Fetal
Modality/Study Types: MR
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Vaginal bleeding and previous C-section.

Case Images


Placenta accreta


MR-Single shot fast spin echo T2 images show intraplacental dark bands and loss of myometrial-placental interface.


Placenta accreta is a disorder of invasive placentation in which the fetal trophoblast invades beyond the uteroplacental interface. This condition includes three grades: placenta accreta, where chorionic villi attach to the myometrium; placenta increta, where the chorionic villi invade the myometrium; and placenta pancreta, where the chorionic villi perforate the uterine myometrium and serosa. Placenta accreta can also be defined by the degree of placental adherence. Focal adherence involves a single placental cotyledon. Partial adherence involves more than one cotyledon, and total adherence involves the entire placenta. Complications of placenta accreta include failure of placental separation from the uterine wall, invasion into adjacent organs, as well as postpartum hemorrhage. Although the cause of placenta accreta is unknown, defects in trophoblast and decidua basalis functioning, as well as defective oxygenation and vascularization of these tissues are hypothesized contributing factors. This is supported by the corelated increase in placenta accreta in individuals with cesarean scarring. It is thought that the abnormal decidua that forms after uterine scarring encourages the pathologic extension of chorionic villus into the myometrium. Risk factors for this condition include placenta previa, previous uterine surgery, and advanced maternal age.

Ultrasound imaging is used for primary screening in individuals at risk for placenta accreta. Ultrasound features that indicate placenta accreta include: the loss of the retroplacental echolucent space, thinning of myometrium, increased vascularity of the interface between myometrium and bladder, abnormal extraplacental blood flow, and the presence of prominent intraplacental lacunae. With placenta pancreta, ultrasound may also exhibit exophytic masses which are indicative of invasion into the bladder. Doppler or color ultrasound may also be used to view areas of discontinuous blood flow found in some cases of placenta accreta.

Magnetic Resonance Imaging is used in coordination with US to evaluate patients for placenta accreta. MRI is particularly useful if sonography is inconclusive for placenta accreta. MRI can also be useful in defining the area and depth of invasive placentation. Features of placenta accreta on MRI include: a thick, dark intraplacental T2 band, notable heterogeneity of the placenta, lower uterine segment bulging, tenting of the urinary bladder, thinning of the myometrium, and disorganized, hypertrophied intraplacental vascularization.


Derman AY, Nikac V, Haberman S, Zelenko N, Opsha O, Flyer M. MRI of placenta accreta: A new imaging perspective. AJR. 2011May18;197:1514–21.


Abigail Rossman

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