What is the appearance of a hematoma on an Ultrasound? How should hematomas be followed up?
A hematoma may have a variety of appearances on US depending on when it is imaged. If imaged acutely, a hematoma often appears as an ill-defined but predominantly hyperechoic collection. A subacute hematoma becomes more hypoechoic, although a heterogeneous appearance is common. A hematoma starts to resorb from the periphery inward, becoming smaller and more echogenic. In the end, a residual anechoic fluid collection or seroma may persist indefinitely. If a lesion demonstrates the typical sonographic features of a hematoma, follow-up is indicated if the lesion substantially enlarges or becomes symptomatic. A 6-week follow-up study is often obtained to document that the hematoma is resolving, because soft tissue tumors may present initially with intramuscular hemorrhage, which may mask the underlying lesion.