Three-Dimensional Power Doppler Ultrasonography for Diagnosing Abnormally Invasive Placenta and Quantifying the Risk

Abstract

Objective: To test an objective ultrasound marker for diagnosing the presence and severity of abnormally invasive placenta.

Methods: Women at risk of abnormally invasive placenta underwent a three-dimensional power Doppler ultrasound scan. The volumes were examined offline by a blinded observer. The largest area of confluent three-dimensional power Doppler signal (Area of Confluence [Acon], cm) at the uteroplacental interface was measured and compared in women subsequently diagnosed with abnormally invasive placenta and women in a control group who did not have abnormally invasive placenta. Receiver operating characteristic curves were plotted for prediction of abnormally invasive placenta and abnormally invasive placenta requiring cesarean hysterectomy.

Results: Ninety-three women were recruited. Results were available for 89. Abnormally invasive placenta was clinically diagnosed in 42 women; 36 required hysterectomy and had abnormally invasive placenta confirmed histopathologically. Median and interquartile range for Acon was greater for abnormally invasive placenta (44.2 [31.4-61.7] cm) compared with women in the control group (4.5 cm [2.9-6.6], P<.001) and even greater in the 36 requiring hysterectomy (46.6 cm [37.2-72.6], P<.001). Acon rose with histopathologic diagnosis: focal accreta (32.2 cm [17.2-57.3]), accreta (59.6 cm [40.1-89.9]), and percreta (46.6 cm [37.5-71.5]; P<.001 analysis of variance for linear trend). Receiver operating characteristic analysis for prediction of abnormally invasive placenta revealed that with an Acon of 12.4 cm or greater, 100% sensitivity (95% confidence interval [CI] 91.6-100) could be obtained with 92% specificity (95% CI 79.6-97.6); area under the curve is 0.99 (95% CI 0.94-1.0). For prediction of abnormally invasive placenta requiring hysterectomy, 100% sensitivity (95% CI 90.3-100) can be obtained with an Acon of 17.4 cm or greater with 87% specificity (95% CI 74.7-94.5; area under the curve 0.98 [0.93-1.0]).

Conclusion: The marker Acon provides a quantitative means for diagnosing abnormally invasive placenta and assessing severity. If further validated, subjectivity could be eliminated from the diagnosis of abnormally invasive placenta.

Level of evidence: II.

Conflict of interest statement

Financial Disclosure

The authors did not report any potential conflicts of interest.

Figures

Fig. 1.

Two-dimensional representation of the three-dimensional method used to generate area of confluence. A. The volume in B mode. Lines have been drawn in on the two-dimensional image to demonstrate the uteroplacental interface and the serosal surface of the uterus. B. The B mode volume with the three-dimensional power Doppler signal overlaid. C. The power Doppler signal after the fetal circulation has been removed. D. All power Doppler signal removed except within 1 cm of the uteroplacental interface. E. The power Doppler signal with the flattest plane of the uteroplacental interface at 90° to the eyeline of the observer, the B mode signal removed, and the largest area of power Doppler confluence estimated (yellow outline).

Fig. 2.

The median and 95% confidence intervals of the area of confluence (cm2) for the following comparisons. A. The clinical diagnosis of not abnormally invasive placenta (AIP) (n=47, range 0.5–29.7 cm2) compared with AIP (n=42, range 12.7–150.4 cm2, P<.001). B. Left two box plots illustrate patients without AIP who did not have a hysterectomy (no, n=44, range 0.5–29.7 cm2) or who did have a hysterectomy (yes, n=3, range: 2.2–9.4 cm2P=nonsignificant). Right two box plots illustrate patients with AIP who did not have a hysterectomy (no, n=6, range 12.7–33.6 cm2) or who did have a hysterectomy (yes, n=36, range 18.7–150.4 cm2, P<.005). C. Patients histopathologically confirmed as not AIP (n=3), focal accreta (n=5, range 18.7–61.1 cm2), accreta (n=9, range 23.9–102.6 cm2), or percreta (n=22, range 24.9–150.4 cm2, P<.001). D. Clinical grade was greater for all grades relative to control (P<.001). Grade 2 (n=12, median 32.2 cm2, range 18.7–61.1); grade 3 (n=6, median 54.7 cm2, range 12.7–89.3); grade 4 (n=15, median 45.7 cm2, range 24.9–102.6); grade 5 (n=8, median 59.6 cm2, range 43.0–150.4); and grade 6 (n=2, median 126.6 cm2, range 113.3–141.8). *See Table 1 for definition of clinical grades.

Fig. 3.

Receiver operator curves for the prediction of abnormally invasive placenta using area of confluence. A. Receiver operating characteristic curve for any clinically diagnosed abnormally invasive placenta (all grades) relative to controls. Area under the curve is 0.99, P<.001. B. Receiver operator characteristic curve for any histopathologically confirmed abnormally invasive placenta significant enough to warrant hysterectomy relative to controls (not abnormally invasive placenta and clinically diagnosed abnormally invasive placenta managed with manual removal of placenta). Area under the curve is 0.98, P<.001.