A hematoma is a collection of blood that has leaked from damaged blood vessels and accumulated in the surrounding tissues. On ultrasound, the appearance of a hematoma changes significantly over time as the blood clots and is gradually reabsorbed. A fresh hematoma may appear echogenic or hyperechoic due to clot formation, then becomes increasingly hypoechoic and complex as the clot begins to break down, and may eventually appear as a simple, anechoic fluid collection. Understanding these time-dependent changes is important because a hematoma can be confused with other pathologies depending on its age. Ultrasound is also used to guide drainage of large or symptomatic hematomas.
Sonography Term