ORIGINAL ARTICLE
Year : 2023 | Volume
: 21 | Issue : 2 | Page : 83--87
Accuracy of ultrasound and magnetic resonance imaging in predicting placenta accreta: A retrospective study
Premkumar Jaisankar1, M Vasantha Kumar2, R Rajesh Gowtham2, T Vinoth2,
1 Department of Radiology, MGM Healthcare, Chennai, Tamil Nadu, India
2 Department of Radiology, ACS Medical College and Hospital, Chennai, Tamil Nadu, India
Correspondence Address:
Dr. T Vinoth
No. 112, Canal Bank Road, CIT Nagar, Chennai - 600 035, Tamil Nadu
India
Abstract
Background: Placenta accreta can cause significant morbidity and mortality in pregnant women. Timely diagnosis is essential for management. This study aimed to evaluate the accuracy of ultrasound (USG) and magnetic resonance imaging (MRI) techniques in predicting placenta accreta. Methodology: A retrospective study was conducted at our institute from April 2014 to September 2017. Pregnant women with suspected placenta accrete were recruited for the study. Medical records of pregnant women who have undergone both USG and prenatal MRI were included. The accuracy of USG and MRI was compared. Results: Among the 56 cases evaluated in the study, the diagnosis was accurately obtained with ultrasonography in 75% of cases and with MRI in 68.51% of cases. Sensitivity for placenta accreta was 97.29% for USG and 78.37% for MRI. Specificities were 31.57% for USG and 47.05% for MRI. The positive predictive value was 73.46% for USG and 76.31% for MRI. Conclusion: Although a definite demarcation could not be obtained from the sensitivity, specificity, and positive predictive value of the placenta accrete with ultrasonography and MRI, the diagnostic accuracy may be taken as a definite pointer. Hence, ultrasonography remains the mainstay of diagnosis for placenta accrete; and MRI can be considered complementary in cases with few USG signs.
How to cite this article:
Jaisankar P, Kumar M V, Gowtham R R, Vinoth T. Accuracy of ultrasound and magnetic resonance imaging in predicting placenta accreta: A retrospective study.Curr Med Issues 2023;21:83-87
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How to cite this URL:
Jaisankar P, Kumar M V, Gowtham R R, Vinoth T. Accuracy of ultrasound and magnetic resonance imaging in predicting placenta accreta: A retrospective study. Curr Med Issues [serial online] 2023 [cited 2023 Jun 9 ];21:83-87
Available from: https://www.cmijournal.org/text.asp?2023/21/2/83/373760 |
Full Text
Introduction
The term placenta accreta is used when there is pathological penetration of the placenta into the wall of the uterus. Currently, it is a major cause of morbidity and mortality among pregnant women. Placenta accreta has been classified based on the degree of penetration into superficial invasions (placenta accreta), middle-layer invasions (placenta increta), and deep invasions (placenta percreta). For the convenience of this study, all these types are considered placenta accreta.
Placenta accreta is closely associated with cesarean section.[1],[2] Moreover, so, with a rise in the rate of cesarean section, the incidence of placenta accrete is also increasing. It has risen from 0.8/1000 deliveries in the 1980s to 3/1000 deliveries in the last decade.[3],[4],[5],[6],[7],[8] Although the reasons for the increased incidence of placenta accrete are multifactorial, its association with the cesarean section is explained by the fact that the place placental penetration is mostly in the previous hysterotomy area.[6],[8],[9] Various other risk factors include the age of the mother and high parity, previous surgeries on the uterus, previous uterine curettage, radiation exposure to the uterus, endometrial ablation procedures in past, and other anomalies of the uterus, hypertensive disorders of pregnancy, and smoking.[5],[6],[10],[11],[12],[13],[14],[15] Studies have shown that placenta accreta is associated with poor neonatal outcomes including preterm birth, low birth weight, small for gestational age, and reduced APGAR score.[11]
Antepartum identification of placenta accretes is commonly done in the second or third trimester using ultrasonography. The commonly observed ultrasonography findings are loss of normal hypoechoic retroplacental zone,[11] multiple vascular lacunae (irregular vascular spaces) within the placenta, giving a “swiss cheese” appearance,[16],[17],[18] blood vessels or placental tissue bridging uterine placental margin, myometrial–bladder interface, or crossing uterine serosa,[19] and the retroplacental myometrial thickness of <1 mm.[11] Numerous coherent vessels are visualized with three-dimensional power Doppler in basal view.[20]
Studies comparing magnetic resonance imaging (MRI) with ultrasound (USG) for the identification of placenta accreta have shown conflicting results.[16],[21]
Objectives
The objective of this study was to evaluate the accuracy of USG and MRI techniques in predicting placenta accreta.
Methodology
Study design and study setting
A descriptive retrospective analysis of all medical records of patients with suspicion of placenta accreta referred to the hospital from April 2014 to September 2017 was done.
Study population
The study population included pregnant women with both USG and prenatal MRI for suspicion of placenta accreta. The clinical data of the patient were recorded in a proforma.
Methods
The USG and MRI for these patients were performed by radiologists with experience of 5–10 years and specialized in fetal medicine. The equipment used was IU 22 system (Philips Medical Systems, Bothell, WA, USA) and the GE Voluson 730 or E8 (GE Medical Systems, Zipf, Austria) with 4–9 MHz or 5–9 MHz transabdominal transducers and 3–9 MHz and 4–8 MHz endovaginal transducers. MRI was performed with a 1.5 Tesla scanner (Siemens Magnetom-Avanto, Siemens Magnetom-vision [Siemens Medical Solutions], Philips Achieva). The MRI protocol included T1-weighted sequences in the sagittal and axial planes, single-shot fast spin echo T2-weighted magnetic resonance sequences (HASTE, single-shot TSE), and true fast imaging with steady-state precession (TrueFISP, FIESTA) in the axial, sagittal, and coronal planes. Seven MRI scans were done after intravenous injection of gadolinium, and six were MR diffusion-weighted imaging. No fetal sedation was used. For the purpose of the study, USG images and MRI were blindly reassessed external reviewers. Blinding was done regarding the diagnosis of the patient.
Operational definitions
In patients where pathologic examination was not possible, and the final diagnosis was done as per the clinical information provided at the time of delivery and surgery. The placenta was considered accreta when the delivery was impossible and as percreta when it was evident that the placenta had reached the uterine serosa or the adjacent organs.[5]
Sample size calculation
The sample size was calculated assuming the sensitivity of USG and MRI in detecting placenta accreta as 100%–76.9%, respectively, as per a study by Riteau et al.[22] By considering the 80% power and 2:1 positive-to-negative allocation ratio, the proposed sample size was 51. After consideration of 10% lost to follow-up, the final sample size considered in the study was 56.
Statistical analysis
The placenta accretes results as per USG and MRI results as count variables using frequency and percentages. The sensitivity, specificity, predictive values, and diagnostic accuracy of the USG and MRI in predicting placenta accreta, along with their 95% confidence interval have been presented. USG was used as a gold standard test. P < 0.05 was considered statistically significant. Data were analyzed using coGuide software, V.1.03 (BDSS, Bangalore, India).[23]
Results
All the participants were between 21 and 32 years of age. Among them, 30 women were the second gravida and 26 women were the third gravida. USG scans and MRIs were performed in the third trimester for all pregnant women. All patients are delivered by lower-segment cesarean section.
There was no statistically significant difference between the two groups in USG outcome parameters such as intraplacental lacunae, thinning or disappearance of the myometrium, thinning or disruption of the hyperechogenic uterine serosa–bladder wall interface, increased vascularization at the uterine serosa–bladder wall interface, irregular bladder wall, and pseudotumoral appearance of placenta and uterine bulging (P > 0.05). There was a statistically significant difference between the two groups in USG outcome parameters such as loss of the normal retroplacental clear space, vascularization perpendicular to the uterine wall, and exophytic uterine masses [P < 0.05, [Table 1]].{Table 1}
There was no statistically significant difference between the two groups in MRI outcome parameters such as disruption of the interface between placenta and myometrium on T2-weighted images, the extension of the placenta on T2-weighted images, dark intraplacental bands, and thinning or disappearance of the myometrium, dark intraplacental bands, and disruption of the interface between placenta and myometrium and uterine bulging and dark intraplacental bands (P > 0.05). There was a statistically significant difference between the two groups in MRI outcome parameters such as uterine bulging, dark intraplacental bands on T2-weighted images, thinning or disappearance of the myometrium, and the presence of neovessels [P < 0.05, [Table 2]].{Table 2}
The sensitivity for placenta accreta was 97.29% for USG and 78.37% for MRI. Specificities were 31.57% for USG and 47.05% for MRI. The positive-predictive value was 73.46% for USG and 76.31% for MRI. The diagnostic accuracy was 75% of cases with ultrasonography and in 68.51% with MRI [Table 3].{Table 3}
Discussion
As per the existing literature, the sensitivity of Doppler USG in predicting placenta accreta arrays is from 33% to 100% and its specificity is from 50% to 96%.[20],[24],[25],[26],[27],[28],[29] and the sensitivity of MRI varies from 38% to 100% and its specificity from 55% to 100%.[20],[25],[26],[27],[28],[29],[30]
D'Antonio et al.[30],[31] reported USG sensitivity of 90.7% and MRI sensitivity of 94.4% and a specificity of 96.9% for USG and 84% for MRI. While the sensitivity is similar to that of the present study, there is a wide difference in specificity; this difference can be attributed to the large sample size, the inclusion of multiple study findings, and the inclusion of the study population in which only one investigation was. The present study found a lower specificity of USG, perhaps because, as in Comstock et al.,[18] placenta accrete was diagnosed even of one of the features was present. This can lead on to an increase in the number of false-positive diagnoses and a reduction in the overall specificity of the test.
The sensitivity observed for “loss of the normal retroplacental clear space” in the present study was higher than those found in the literature.[18],[30] Cali et al.[32] found the same results.
As in the literature,[31],[32],[33],[34],[35],[36],[37] this study also found the statistical significance of MRI when dark intraplacental bands were associated with thinning and disappearance of the myometrium.
Ultrasonography is still considered the imaging modality with high sensitivity for the diagnosis of placenta accrete due to its accuracy, cost-effective nature, and being noninvasive and less time-consuming procedure. MRI can be considered a complement to ultrasonography, in cases where there are very few USG signs. MRI is very useful as it will reveal signs which may not be picked up by USG such as dark intraplacental bands, this feature can be used to confirm the diagnosis of placenta accreta.
As cesarean section rates are on the rise worldwide, the best strategy would be: to identify the early diagnosis and treatment strategy. There is a lack of randomized clinical trials and cohort studies done in cases of placenta accreta and not much evidence is available on the diagnosis and management. Such studies are needed to recommended in future to optimize care and to enable antepartum diagnosis of placenta accreta, thereby preventing morbidity and mortality caused.
Conclusion
Based on the diagnostic accuracy, it can be concluded that ultrasonography remains the backbone of diagnosis for placenta accrete; and MRI can be considered a complementary diagnostic modality to ultrasonography, especially when there are limited USG signs.
Limitations
Study is a hospital-based study performed at a single tertiary center. The generalizability of the study outcome is limited.
Acknowledgments
We acknowledge the technical support in manuscript editing by “Evidencian Research Associates.”
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
Ethical statement
The Institutional Ethics Review Board approved the conduct of this study (Ref: CSP-MED/16/JUN/29/66).
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