Department of Radiology and Biomedical Imaging, University of California San Francisco, 505 Parnassus Ave., Box 0628, San Francisco, CA, 94131, USA.
Department of Pathology, University of California San Francisco, San Francisco, USA.
Abdom Radiol (NY). 2019 Jul;44(7):2572-2581. doi: 10.1007/s00261-019-02008-0.
To evaluate correlation of "placental bulge sign" with myometrial invasion in placenta accreta spectrum (PAS) disorders. Placental bulge is defined as deviation of external uterine contour from expected plane caused by abnormal outward bulge of placental tissue.
In this IRB-approved, retrospective study, all patients undergoing MRI for PAS disorders between March 2014 and 2018 were included. Patients who delivered elsewhere were excluded. Imaging was reviewed by 2 independent readers. Surgical pathology from Cesarean hysterectomy or pathology of the delivered placenta was used as reference standard. Fisher's exact and kappa tests were used for statistical analysis.
Sixty-one patients underwent MRI for PAS disorders. Two excluded patients delivered elsewhere. Placental bulge was present in 32 of 34 cases with myometrial invasion [True positive 32/34 = 94% (95% CI 0.80-0.99)]. Placental bulge was absent in 24 of 25 cases of normal placenta or placenta accreta without myometrial invasion [True negative = 24/25, 96% (95% CI 80-99.8%)]. Positive and negative predictive values were 97% and 96%, respectively. Placental bulge in conjunction with other findings of PAS disorder was 100% indicative of myometrial invasion (p < 0.01). Kappa value of 0.87 signified excellent inter-reader concordance. In 1 false positive, placenta itself was normal but the bulge was present. Surgical pathology revealed markedly thinned, fibrotic myometrium without accreta. One false-negative case was imaged at 16 weeks and may have been imaged too early.
Placental bulge in conjunction with other findings of invasive placenta is 100% predictive of myometrial invasion. Using the bulge alone without other signs can lead to false-positive results.
评估胎盘外凸征与胎盘植入谱系（PAS）疾病中子宫肌层浸润的相关性。胎盘外凸定义为胎盘组织异常向外突出导致子宫外部轮廓偏离预期平面。
本研究为经机构审查委员会批准的回顾性研究，纳入 2014 年 3 月至 2018 年期间因 PAS 疾病行 MRI 检查的所有患者。排除在其他地方分娩的患者。由 2 位独立的阅片者对影像学进行评估。剖宫产子宫切除术的手术病理或已分娩胎盘的病理作为参考标准。采用 Fisher 确切检验和 Kappa 检验进行统计学分析。
61 例 PAS 疾病患者行 MRI 检查。2 例排除患者在其他地方分娩。34 例有子宫肌层浸润的病例中，有 32 例存在胎盘外凸[真阳性 32/34=94%（95%CI 0.80-0.99）]。25 例正常胎盘或无子宫肌层浸润的胎盘植入患者中，24 例胎盘外凸不存在[真阴性 24/25，96%（95%CI 80-99.8%）]。阳性预测值和阴性预测值分别为 97%和 96%。胎盘外凸结合 PAS 疾病的其他表现，对子宫肌层浸润的提示率为 100%（p<0.01）。0.87 的 Kappa 值表明两位阅片者的一致性极好。1 例假阳性病例中，胎盘本身正常，但存在外凸。手术病理显示，明显变薄的纤维化子宫肌层，无粘连。1 例假阴性病例在 16 周时进行影像学检查，可能检查过早。
胎盘外凸结合其他侵袭性胎盘的表现，对子宫肌层浸润的提示率为 100%。单独使用外凸而无其他征象可能导致假阳性结果。
