Ultrasound as a Sole Modality for Prenatal Diagnosis of Placenta Accreta Spectrum: Potentialities and Pitfalls

Abstract

Background Placenta accreta spectrum (PAS) is a significant cause of maternal and neonatal mortality and morbidity. Its prevalence has been rising considerably, primarily due to the increasing rate of primary and repeat cesarean sections. Accurate prenatal identification of PAS allows optimal management because the timing of delivery, availability of blood products, and recruitment of skilled anesthesia, and surgical team can be arranged in advance. Aims and Objectives This study aimed to (1) study the ultrasound and color Doppler features of PAS, (2) correlate imaging findings with clinical and per-operative/histopathological findings, and (3) evaluate the accuracy of ultrasound for the diagnosis of PAS in patients with previous cesarean section. Materials and Methods This prospective study was conducted in radiology department of a tertiary care hospital. After screening 1,200 pregnant patients, 50 patients of placenta previa with period of gestation ≥ 24 weeks and history of at least one prior cesarean section were included in the study. Following imaging features were evaluated: (1) gray scale covering intraplacental lacunae, disruption of uterovesical interface, myometrial thinning, loss of retroplacental clear space, and focal exophytic masses; and (2) color Doppler covering intraplacental lacunar flow, hypervascularity of uterine serosa-bladder wall interface, and perpendicular bridging vessels between placenta and myometrium. Study Design Present study is a prospective one in a tertiary care hospital. Results Of the 19 PAS cases, 18 were correctly diagnosed on ultrasonography (USG) and confirmed either by histopathological analysis of hysterectomy specimen or per-operatively due to difficulty in placental removal. PAS was correctly ruled out in 27 of 31 patients. The diagnostic accuracy of USG was 90%. The sensitivity, specificity, positive, and negative predictive values were 94.7, 87.1, 81.8, and 96.4%, respectively. Conclusion Ultrasound is indispensable for the evaluation of pregnant patients. It is an important tool for diagnosing PAS, thereby making the operating team more cautious and better equipped for difficult surgery and critical postoperative care. It can be relied upon as the sole modality to accurately rule out PAS in negative patients, thereby obviating unnecessary psychological stress among patients due to possible hysterectomy.

Keywords: Doppler; antepartum hemorrhage; cesarean; hysterectomy; maternal mortality; morbidly adherent placenta; placenta accrete; placenta increta; placenta percreta; placental lacunae.

Conflict of interest statement

Conflicts of Interest There are no conflicts of interest to declare.

Indian Radiological Association. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. ( https://creativecommons.org/licenses/by-nc-nd/4.0/ ).

Figures

Fig. 1

Algorithm of methodology. CS, cesarean section; USG, ultrasonography. BPV, bleeding per vaginum; D&C, dilation and curettage; FHS, fetal heart sound; LMP, last menstrual period; LPV, leaking per vaginum; MAPP, morbidly adherent placenta previa; POG, period of gestation.

Fig. 2

A 28-year-old patient with previous two CS presented with APH. Transabdominal scan shows central placenta Previa. Heterogeneous placenta showing multiple large irregular-shaped lacunae with nonechogenic walls throughout its parenchyma (grade 3). Loss of clear space, marked myometrial thinning, and discontinuity (arrow) of echogenic bladder line with placental invasion into UB suggestive of placenta percreta. Color and spectral Doppler images show increased periuterine vascularity of low-resistance arterial flow. Lacunae show high-velocity venous flow. Intraoperative photograph shows thin and highly vascular LUS with densely adhered placental tissue. APH, antepartum hemorrhage; CS, cesarean section; UB, urinary bladder.

Fig. 3

Placenta percreta in a 29-year-old lady with two previous CS presented with APH. (A) TAS shows exophytic mass of same echogenicity as placenta invading into UB (arrow) with no identifiable myometrium, uterine serosa, or bladder wall in between. (B) Axial image at same level shows the exact site of invasion on the left of midline. (C) Color Doppler image ofBshows extensive hypervascularity at uterovesical interface. (D) Intraoperative photograph shows the exophytic mass of placenta protruding outside the uterine serosa from the anterior wall of lower uterine segment. CS, cesarean section; TAS, transabdominal sonography; UB, urinary bladder.

Fig. 4

Placenta accreta vera in a 38-year-old asymptomatic lady with prior 1 CS, 1 D and C, and 1 hysterotomy. (A) Central PP. Echogenic line of uterine serosa–bladder wall interface intact. (B) Subplacental hypervascularity, aberrant vessels crossing between the placental surfaces. (C, D) Loss of clear zone, myometrial thinning, and lacunae showing turbulent flow (E) Coronal T2W MRI shows heterogeneous placenta and multiple hypointense bands. (F) Coronal T2-W MRI shows the hypointense line of inner myometrium (arrow) becoming discontinuous on the left side. Outer myometrium and uterine serosa intact. (G) Hematoxylin and eosin stain ×100 of hysterectomy specimen–placental villi (V) invading decidua (D), reaching up to myometrium. CS, cesarean section; MRI, magnetic resonance imaging; T2-W, T2-weighted. C, cervix; D, decidua; F, fetus; L, placental lacunae; M, myometrium; P, placenta; UB, urinary bladder; V, placental villi.

Fig. 5

The ROC curve for the diagnostic significance of intraplacental lacunae. Area under the ROC curve is 92.9% (95% CI: 0.79 to 0.99) which reveals that the grading of intraplacental lacunae is sufficient for discriminating the positive and negative subjects. The best cut-off of grading is lacunar grade greater than 2 and at this point, sensitivity is 84.2% and specificity is 87.1%. CI, confidence interval; ROC, receiver operating characteristic.