MRI in the diagnosis and surgical management of abnormal placentation.

OBJECTIVE

To determine the usefulness of placental magnetic resonance imaging (MRI) in the diagnosis and surgical management of abnormal placentation.

DESIGN

Retrospective follow-up.

SETTING

Buenos Aires, Argentina.

POPULATION: 547 pregnant women.

METHODS

In all cases, a direct and reliable description of abnormal placentation features was obtained by the operating surgeon. Placental MRI was analyzed according to: (1) primary description, (2) invasion topography, (3) modification required to the surgical tactics or techniques and (4) by positive and negative predictive values.

MAIN OUTCOME MEASURES: Ultrasound and MRI findings were compared with surgical results, which were considered a final diagnosis in relation to primary diagnostic indications.

RESULTS

Placental MRI was obtained because of diagnostic doubt in 78 cases, for deep invasion diagnosis in 148 cases and to define the invasion area in 346 cases. Placental MRI allowed accurate demarcation and assessment of the degree of placental invasion, parametrial involvement and cervico-trigonal vascular hyperplasia, permitting changes in the surgical tactical approach. Ultrasound and MRI differences were associated with placenta previa, uterine scar thinning and use of different criteria for placental invasion through definitions or terminology. Six cases of false-negative and 11 of false-positive findings were reported.

CONCLUSION

Placental MRI provides excellent characterization of the degree and extension of placental invasion. Its usefulness in cases of adherent placentation is directly associated to the therapeutic measures, especially where dissection maneuvers are needed. Diagnostic differences between ultrasound and MRI related to the presence or not of placenta previa and uterine scar thinning.