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376: Sonographic findings associated with the diagnosis of invasive placentation

      Objective

      A number of sonographic signs can be indicative of placenta accreta. The purpose of this study was to determine the relative frequency and accuracy of these signs in predicting invasive placentation.

      Study Design

      We performed a retrospective chart review of cases of pathology-proven placenta accreta. Sonographic images were reviewed and 9 ultrasound signs of placenta accreta (previa, loss of myometrial interface (LMI), chaotic intraplacental blood flow, ‘swiss cheese appearance', placenta bulging into bladder, distance of bulge into the bladder, invasion into the bladder, excrescences, and color Doppler crossing vessels) were coded as present, absent or indeterminate. The images were independently reviewed by 2 physicians.

      Results

      Twenty-seven cases of pathology-proven accretas were identified from 2002 to 2008. Of these, 14 (52%) were accretas, 4 (15%) were incretas and 9 (33%) were percretas. The frequency of the sonographic signs are shown in Table 1. The most common sonographic findings associated with all forms of invasive placentation were previa and loss of myometrial interface. Of the 14 cases with a sonographic sign of bladder invasion, only 5 were confirmed on pathology. The sensitivity and specificity of this sonographic finding for the diagnosis of percreta are 55% and 50% respectively. Nine of the 16 patients with a bladder bulge were confirmed to have percretas. The sensitivity and specificity of this sonographic finding for the diagnosis of percreta are 100% and 61% respectively. Calculated bladder bulge distance was significantly different between accretas and percretas; 25 mm vs. 85mm (p value=0.04).
      Tabled 1Sonographic signs associated with invasive placentation.
      PreviaLMICrossing vesselsChaotic flow
      All accretas93%93%82%70%
      BulgeBladder invasion‘Swiss cheese’Excrescence
      All accretas60%52%52%30%

      Conclusion

      The presence of a previa with LMI is the most common finding in patients with accretas. There is a strong association between noted bladder bulge and placenta percreta.