Ultrasound differential diagnosis between amniotic fluid sludge and blood clot from placental edge separation

A 32-year-old G3P1011 patient was followed for a history of loop electrosurgical excision procedure and short cervix in a previous pregnancy. Early transvaginal cervical length at 16 weeks was within normal limits. During a transvaginal ultrasound at 18 weeks of gestation, cervical length was noted to be 3.5 cm. Behind the cervix, amorphous particulate matter was visualized in the amniotic fluid. The matter appeared heterogeneous, wispy, and adjacent to the internal cervical os, but also abutting the edge of the posterior low-lying placenta (Figure, A, yellow arrow; Video). A triangulated anechoic area of placental edge separation was noted immediately inferior to it (Figure, A, white arrow). The particulate matter was noted to be adherent to the placental edge in all views (Figure, A; Video). Initial diagnosis of sludge was considered given the location and history of the cervical procedure. However, given the characteristic heterogeneity with overall less echogenicity (compared with sludge as compared to sludge) (Figure, C), characteristic motion (Video), adherence to the placental edge, and long cervix, a marginal placental hematoma (clot) was suspected. A, Amorphous matter adjacent to the internal cervical os (yellow arrow), abutting the placental edge of low-lying placenta, which has separated by hemorrhage (white arrow). B, Point-of-care ultrasound from patient’s presentation with vaginal bleeding. This is a transabdominal image taken in sagittal view, with a longitudinal cut of the uterus at the same level as in the previous transvaginal image. The same placental edge is seen as in (A). The hematoma now appears as a large clot covering the area of the cervical os, although the cervix is not visible (yellow arrows). C, Transvaginal ultrasound of amniotic fluid sludge (blue arrow) from a different patient. This patient had histology-proven Escherichia coli chorioamnionitis. Amniotic fluid sludge noted to have a brighter appearance, with similar echogenicity to adjacent cervical stroma. Of note, the cervix is short. D, Placental edge (fetal side) after delivery showing the hemorrhagic area at 4-o’clock position, corresponding to the placental edge separation by ultrasound. E, Placental edge (maternal side) after delivery showing the hemorrhagic area at 10-o’clock position, corresponding to the placental edge separation by ultrasound. F, Microscopic appearance of the placenta after delivery, showing the area of hemorrhage attached to the membranes. However, no microscopic finding of abruption (eg, hemosiderin-laden macrophages, intervillous hemorrhage) was found. Kantorowska. Amniotic fluid sludge versus blood clot from placental edge separation. Am J Obstet Gynecol 2022.