Which of the following suggests thrombus formation?

Thrombus formation in the venous system can be suggested by various physical and ultrasound characteristics.

Increased vein diameter is a significant indicator, as veins can become distended and larger in the presence of a thrombus. This dilation occurs because the thrombus obstructs normal blood flow, leading to an accumulation of blood in the affected area.

Decreased echogenicity on ultrasound reflects the acoustic properties of the thrombus. A fresh thrombus, especially one that is not yet fully organized, tends to be echogenic, meaning it reflects less sound waves. This low echogenicity can help in visualizing thrombus formation when assessing the vein.

The presence of a "tail" of thrombus in the lumen is another critical indicator. This tail, often seen extending from the main abdominal portion of the thrombus, represents the active part of the clot that can further propagate if not treated.

When all these characteristics are considered together, they collectively suggest thrombus formation, which leads to the conclusion that all of these factors play a role in identifying thrombus.