After thrombosis is formed, its structure changes under the action of fibrinolytic system and blood flow shock and regeneration of the body.

There are 3 main types of final changes in a thrombus:

1. Soften, dissolve, absorb

After the thrombus is formed, the fibrin in it absorbs a large amount of plasmin, so that the fibrin in the thrombus becomes a soluble polypeptide and dissolves, and the thrombus softens. At the same time, because the neutrophils in the thrombus disintegrate and release proteolytic enzymes, the thrombus can also be dissolved and softened.

The small thrombus dissolves and liquefies, and can be completely absorbed or washed away by the bloodstream without leaving a trace.

The larger part of the thrombus is softened and easily falls off by the blood flow to become an embolus. The emboli block the corresponding blood vessel with the blood flow, which can cause embolism, while the remaining part is organized.

2. Mechanization and Recanalization

Larger thrombi are not easy to dissolve and absorb completely. Usually, within 2 to 3 days after thrombus formation, granulation tissue grows from the damaged vascular intima where the thrombus is attached, and gradually replaces the thrombus, which is called thrombus organization.
When the thrombus is organized, the thrombus shrinks or partially dissolves, and a fissure is often formed inside the thrombus or between the thrombus and the vessel wall, and the surface is covered by proliferating vascular endothelial cells, and finally one or several small blood vessels that communicate with the original blood vessel are formed. Recanalization of blood flow is called recanalization of the thrombus.

3. Calcification

A small number of thrombi that cannot be completely dissolved or organized may be precipitated and calcified by calcium salts, forming hard stones existing in the blood vessels, called phleboliths or arterioliths.