Ultrasonography and color Doppler Ultrasound in Diagnosis of Placenta Previa Accreta

Abstract

It is estimated that 140 000 women die of postpartum hemorrhage per year (ACOG,2006). Although statistically, placenta accreta has now become an important etiology of maternal morbidity and mortality (Dildy, 2002). Owing to the increasing rate of cesarean delivery, there has been a 10-fold rise in the incidence of placenta accreta since the 1970 (Wu et al .,2005). In a recent survey, placenta accreta was even found to have become the leading cause of emergency peripartum hysterectomy which represents 40–60% of cases (Daskalakis et al., 2007) Placenta accreta is a potentially life-threatening obstetric condition that requires a multidisciplinary approach to management. The incidence of placenta accreta has increased and seems to parallel the increasing cesarean delivery rate. Women at greatest risk of placenta accreta are those who have myometrial damage caused by a previous cesarean delivery with either an anterior or posterior placenta previa overlying the uterine scar. Ultrasound is the recommended first step in the diagnosis of placenta previa accreta (Doumouchtis and Arulkumaran, 2010). Color Doppler ultrasound has been suggested to aid in the diagnosis of placenta previa accreta because it highlights abnormal areas of hypervascularity with dilated blood vessels within the placental and uterine tissues (Chou et al., 2000; Levine et al., 1997; Lerner et al., 1995). Color Doppler ultrasound can improve the accuracy of the diagnosis of placenta previa accreta, since the depth of invasion of the placenta into the uterine myometrium or serosa can be more accurately determined, especially in cases where the placenta is located anteriorly (Comstock et al., 2005; Twickler et al., 2000). Color Doppler will show that some of the placental sinuses traverse the uterine wall with turbulent blood flow which extending from the placenta into surrounding tissues and this is very sensitive and correctly identified all patients with accreta and not present in any patients without (Lerner et al., 1995). Color Doppler sonographic features of placenta previa accreta were described as follow: 1. Absence of subplacental vascular signals in the areas lacking the peripheral subplacental hypoechoic zone → (A). 2. Dilated vascular channels with diffuse lacunar flow pattern scattered throughout the whole placenta and the surrounding myometrial or cervical tissues. High-velocity pulsatile venous-type flow was found in the sonolucent vascular spaces → (D). 3. Interphase hypervascularity with abnormal blood vessels linking the placenta to the bladder with high diastolic arterial blood flow → (H). 4. Irregular vascular lakes with focal turbulent lacunar flow pattern distributed regionally or focally within the intraparen-chymal placental area → (F). (Chou et al., 2000)