Placental adhesion disorder: magnetic resonance imaging features and a proposal for a structured report

Placenta accreta spectrum in early and late pregnancy from an imaging perspective. A scoping review

Placenta accreta spectrum (PAS) disorders (with increasing order of the depth of invasion: accreta, increta, percreta) are quite challenging for the purpose of diagnosis and treatment. Pathological examination or imaging evaluation are not very dependable when considered as stand-alone diagnostic tools. On the other hand, timely diagnosis is of great importance, as maternal and fetal mortality drastically increases if patient goes through the third phase of delivery in a not well-suited facility. A multidisciplinary approach for diagnosis (incorporating clinical, imaging, and pathological evaluation) is mandatory, particularly in complicated cases. For imaging evaluation, the diagnostic modality of choice in most scenarios is ultrasound (US) exam; patients are referred for MRI when US is equivocal, inconclusive, or not visualizing placenta properly. Herewith, we review the reported US and MRI features of PAS disorders (mainly focusing on MRI), going over the normal placental imaging and imaging pitfalls in each section, and lastly, covering the imaging findings of PAS disorders in the first trimester and cesarean section pregnancy (CSP).

Developments in functional imaging of the placenta

The placenta is both the literal and metaphorical black box of pregnancy. Measurement of the function of the placenta has the potential to enhance our understanding of this enigmatic organ and serve to support obstetric decision making. Advanced imaging techniques are key to support these measurements. This review summarises emerging imaging technology being used to measure the function of the placenta and new developments in the computational analysis of these data. We address three important examples where functional imaging is supporting our understanding of these conditions: fetal growth restriction, placenta accreta, and twin-twin transfusion syndrome.

Achados na ressonância magnética do espectro do acretismo placentário: ensaio iconográfico

Resumo Acretismo placentário é uma condição caracterizada pela implantação anormal da placenta, que pode ser subdividida em três espectros de acordo com o seu grau de invasão: placenta acreta (ultrapassa a decídua basal e adere ao miométrio), placenta increta (penetra o miométrio) e placenta percreta (invasão da serosa uterina ou de tecidos/órgãos adjacentes). A incidência de acretismo placentário aumentou significativamente nas últimas décadas, principalmente em função da elevação das taxas de cesarianas, sendo este o seu principal fator de risco. A sua identificação pré-natal precisa permite um tratamento ideal com equipe multidisciplinar, minimizando significativamente a morbimortalidade materna. Os exames de escolha são a ultrassonografia e a ressonância magnética (RM), sendo a RM um método complementar indicado quando a avaliação ultrassonográfica é duvidosa, para pacientes com fatores de risco para acretismo placentário ou quando a placenta tem localização posterior. A RM é preferível também para avaliar invasão de órgãos adjacentes, oferecendo um campo de visão mais amplo, o que melhora o planejamento cirúrgico. Diversas características na RM são descritas no acretismo placentário, incluindo bandas hipointensas em T2 intraplacentárias, protuberância uterina anormal e heterogeneidade placentária. O conhecimento desses achados e a combinação de mais de um critério aumentam a confiabilidade do diagnóstico.

Structured MRI reporting increases completeness of radiological reports and requesting physicians' satisfaction in the diagnostic workup for pelvic endometriosis

PURPOSE

MRI plays an important role in the diagnosis and surgical planning of pelvic endometriosis (PE), and imaging reports should contain all relevant information (completeness). As structured reports are being increasingly utilized, we aimed to evaluate whether structured MRI reporting increases the quality of reports regarding completeness and, consequently, their perceived value by gynecologists, in comparison to free-text reports. We also aimed to compare the diagnostic performance of both formats.

METHODS

We retrospectively included 28 consecutive women with histologically proven PE who underwent MRI within one month before surgery. Two abdominal radiologists (Rd1/Rd2, 3y/12y experience), blinded to clinical and surgical data, individually elaborated free-text reports and, four months later, structured reports. Completeness (defined as description of six key anatomical sites deemed essential for surgical planning in a consensus of four-blinded external experts) and diagnostic performance (sensitivity and specificity) by site (histology as reference) were compared between reports using the McNemar test. The satisfaction of gynecologists was compared using the marginal homogeneity test.

RESULTS

Structured reporting increased completeness for both Rd1 (rectosigmoid, retrocervical/uterosacral ligament, vagina, and ureter) and Rd2 (vagina, ureter, and bladder) (p < 0.05), without compromising sensitivity or specificity at any of the evaluated sites. Gynecologists' satisfaction was superior with structured reports in most comparisons.

CONCLUSION

Structured MRI reports perform better in fully documenting essential features of PE and are similar in terms of diagnostic performance, therefore having higher potential for surgical planning. Gynecologists found them easier to assess and were more satisfied with the information provided by structured reports.

Placental magnetic resonance imaging: normal appearance, anatomical variations, and pathological findings

Placental magnetic resonance imaging (MRI) has been increasingly requested, especially for the evaluation of suspected cases of placental adhesive disorders, generally known as placenta accreta. Abdominal radiologists need to become familiar with normal placental anatomy, anatomical variations, the current terminology, and major placental diseases that, although rare, are important causes of maternal and fetal morbidity and mortality. The aim of this didactic pictorial essay is to illustrate various findings on placental MRI, as well as to emphasize the importance of communication between radiologists and obstetricians in the search for best practices in the management of the affected patients.