The importance of bladder volume in the ultrasound diagnosis of placenta accreta spectrum disorders

Objective To assess how a quantifiable measure of vascularity—i.e. abnormal confluence (A con ) in the subplacental myometrium observed by three‐dimensional power‐Doppler ultrasonography—changes with different bladder volumes. Methods In a prospective observational study, women referred to a tertiary UK center with suspected PAS disorders were recruited between August 2016 and May 2017. The largest area of confluent three‐dimensional power‐Doppler signal (A con ) at the uteroplacental interface was estimated under two bladder volumes differing by at least 200  mL . Results A con was calculated for 14 women, of whom seven were subsequently found to have PAS disorders. For these seven women, log(A con ) was significantly greater when measured with a filled bladder than when measured with an unfilled bladder ( P <0.001). Conclusion Objective evidence was found for a quantifiable difference in vascularity in the myometrium with bladder volume among women with PAS disorders. This difference has sufficient magnitude to influence the potential of A con as a diagnostic marker.