Magnetic resonance imaging improves specificity of placenta accreta spectrum requiring hysterectomy compared to ultrasound

Abstract

BackgroundMagnetic resonance imaging (MRI) has been increasingly used as an adjunct to ultrasound (US) imaging for Placenta Accreta Spectrum (PAS) assessment and preoperative surgical planning, but its value is not yet established. The US-based Placenta Accreta Index (US-PAI) is a well-validated standardized approach for PAS evaluation. PAS-MR markers have been outlined in a joint guideline from Society of Abdominal Radiology and European Society of Urogenital Radiology. ObjectiveTo compare PAS-MR parameters and US-PAI in pregnancies at high risk for PAS and assess MRI's additional diagnostic value for PAS requiring cesarean hysterectomy. Study designThis was a single-center retrospective study of pregnant patients who received MRI in addition to US due to suspected PAS. US-PAI and PAS-MR parameters were obtained. Student's t-test and Fisher's exact test between the primary outcome (hysterectomy vs. no hysterectomy) were performed. Diagnostic performance between MRI and US-PAI were assessed using multivariable logistic regression, receiver operating characteristics (ROC) curve, DeLong test, McNemar test and relative predictive value test. ResultsA total of 82 patients were included in the study; 41 of whom required hysterectomy. All patients who underwent hysterectomy had International Federation of Gynecology and Obstetrics (FIGO) clinical evidence of PAS at the time of delivery. Multiple parameters of US-PAI and PAS-MR predicted hysterectomy, with greatest dimension of invasion by MRI as the best quantitative predictor. At 96% sensitivity for hysterectomy, cutoff values were 3.5 for US-PAI and 2.5 cm for greatest dimension of invasion by MRI. Using this sensitivity, greatest dimension of invasion by MRI had higher specificity (p = 0.0016) and positive predictive value (PPV) (p = 0.0018) than those of US-PAI, indicating an improved diagnostic threshold.Conclusion: In a suspected high-risk group for PAS, MRI identifies more patients who will not need hysterectomy compared to US-based criterion only. MRI has the potential to aid patient counseling, surgical planning, and delivery timing, including preterm delivery decisions for patients with PAS requiring hysterectomy.