MRI Features of Placental Adhesion Disorders and their Diagnostic Significance

Abstract

Introduction: Placental Adhesion Disorder (PAD) is a critical obstetric condition in which a deficient decidua basalis allows chorionic villi to penetrate the myometrium, ranging from superficial attachment (accreta vera) to deep invasion (increta) or transmural extension into adjacent organs (percreta). While ultrasonography remains the primary diagnostic tool, Magnetic Resonance Imaging (MRI) serves as a vital adjunct for evaluating posterior placentation or inconclusive sonographic findings, offering a reported sensitivity of 75-100% together with precise mapping of extrauterine extension. Aim: To evaluate the diagnostic accuracy of specific MRI features and to determine their correlation with definitive intraoperative outcomes in patients with suspected PAD. Materials and Methods: This longitudinal study was conducted in the Department of Radiodiagnosis, Government T D Medical College, Alappuzha, Kerala, India, over a period of one and a half year. A cohort of 20 women above 18 years of age presenting with risk factors such as placenta previa or prior myomectomy, or with sonographic suspicion of PAD, was included. Participants underwent MRI evaluation followed by surgical intervention at the same facility. Data were collected using a semi-structured proforma detailing sociodemographic profile, obstetric history, and specified MRI markers. Findings were correlated with intraoperative results, and analysed using the Chi-square test in Statistical Package for Social Sciences (SPSS) version 26. A p-value <0.05 was considered statistically significant. Results: The study included 20 patients, predominantly in the 31-40 years age group (65%), with 75% multiparous and 70% having a prior history of Lower-Segment Caesarean Section (LSCS); obstetric hysterectomy was required in 80% of the cases. MRI demonstrated variable diagnostic performance in predicting hysterectomy. Abnormal uterine bulge and subserosal hypervascularity each demonstrated a sensitivity of 100%, specificity of 50%, Positive Predictive Value (PPV) of 88.9%, Negative Predictive Value (NPV) of 100% and accuracy of 90%, with a statistically significant association (p-value=0.032). Placental bulge, irregular myometrial interface and myometrial thinning each showed 100% sensitivity, 25% specificity, 84.2% PPV, 100% NPV and 85% accuracy (p-value=0.200). Placental heterogeneity demonstrated 81.3% sensitivity, 50% specificity, 86.7% PPV, 40% NPV and 75% accuracy (p-value=0.249); dark placental bands showed 62.5% sensitivity, 50% specificity, 83.3% PPV, 25% NPV and 60% accuracy (p-value=1.000). Placental protrusion had low sensitivity (31.3%) but very high specificity (100%), with 100% PPV, 26.7% NPV and 45% accuracy (p-value=0.530). Abnormal placental vascularity showed 25.0% sensitivity, 75% specificity, 80.0% PPV, 20% NPV and 35% accuracy (p-value=1.000). Conclusion: The high sensitivity of features such as subserosal hypervascularity, uterine bulge and myometrial thinning ensures that the majority of invasive cases are detected, thereby, facilitating the surgical preparedness required for obstetric hysterectomy. Abnormal uterine bulge and subserosal hypervascularity emerged as the most statistically significant and reliable predictors of surgical outcome, whereas placental protrusion, though infrequent, was highly specific for advanced invasion. A multiparametric MRI approach focused on these key features is recommended for accurate surgical planning; larger prospective studies are needed to refine diagnostic thresholds.