Rouleaux formation in an abdominal aortic aneurysm
The blood flow within an abdominal aortic aneurysm can show different patterns such as flow separation, recirculation and possible transition to turbulence. Flow recirculation can sometimes be noted in large aneurysms when using B-mode image. Red blood cells (RBCs) can adhere together forming stacks of coin like structures called rouleaux. This can be seen in large abdominal aortic aneurysms where recirculation of the flow is present.
Using B-mode, the patent aortic lumen of large abdominal aortic aneurysms may appear echogenic rather than anechoic due to RBCs aggregation describing vortexes patterns.
TAKE HOME MESSAGE: It is important to be aware of the ultrasound appearance of rouleaux formation as this should not be mistaken for aortic dissection or mural thrombus.