What is the condition characterized by multiple, irregular, turbulent-flow vascular spaces within the placenta?

Vascular Lacunae

The diagnostic ultrasound finding of multiple, irregular, turbulent-flow vascular spaces within the placenta is called "vascular lacunae" or "placental lacunae," and this is a hallmark sonographic feature of placenta accreta spectrum (PAS) disorder. 1, 2

Key Diagnostic Features

Vascular lacunae represent the most important and sensitive ultrasound finding for PAS, with the highest sensitivity and positive predictive value among all sonographic markers. 2 These are characterized by:

• Multiple, large, irregular sonolucent spaces within the placenta that appear as dark areas on gray-scale ultrasound 2
• Turbulent lacunar blood flow on color Doppler imaging, which is the most common and helpful Doppler finding for placenta accreta 1, 2
• Irregular distribution throughout the placental tissue, distinguishing them from normal placental lakes 3

Pathophysiologic Basis

The vascular lacunae visible on ultrasound correspond to massively dilated uterine vessels at the uteroplacental interface, not placental vessels. 1 Histologically, these represent:

• Dilated anastomosing vasculature in the myometrium beneath the abnormally adherent placenta 1
• Intrusion of intact villous tissue into massively dilated vessels at the placental-myometrial interface 1
• Spaces variably lined by endothelium or trophoblast that may give the appearance of vascular continuity between placenta and uterus 1

Critical Associated Findings

When vascular lacunae are identified, you must immediately assess for other PAS features:

• Loss of the retroplacental clear zone (normal hypoechoic zone between placenta and myometrium) 1, 2, 3
• Myometrial thickness <1 mm, which has 97% sensitivity and 92% specificity when numerous coherent vessels are present 4
• Placenta previa, present in >80% of PAS cases 1
• Increased subplacental vascularity and vessels bridging from placenta to bladder on Doppler 2, 4

Diagnostic Performance

Ultrasound identification of vascular lacunae achieves:

• Sensitivity of 77-93% for PAS diagnosis 2
• Positive predictive value of 65-93% 2
• Average sensitivity of 90.72% and specificity of 96.94% in systematic review of 3,707 pregnancies 1, 2

Critical Differential Diagnosis

You must distinguish vascular lacunae of PAS from benign placental lakes, which are clinically insignificant venous spaces. 3 The key differentiators are:

• PAS lacunae occur with loss of retroplacental clear zone, thinned myometrium, and turbulent flow 3
• PAS lacunae are multiple, irregular, and associated with placenta previa 1, 3
• Benign placental lakes maintain normal retroplacental zone and myometrial thickness 3

Immediate Management When Lacunae Identified

Transfer care immediately to a level III or IV maternal care facility with multidisciplinary expertise when vascular lacunae suspicious for PAS are identified. 4, 3 This includes:

• Maternal-fetal medicine subspecialists and experienced pelvic surgeons 4
• Blood bank capable of massive transfusion protocols 4
• Planned cesarean delivery at 34 0/7 to 35 6/7 weeks gestation 4

Common Pitfall

Never rely on absence of ultrasound findings to exclude PAS—clinical risk factors (prior cesarean delivery, placenta previa, advanced maternal age) remain equally important predictors as the presence of vascular lacunae. 4