A seroma is a pocket of clear serous fluid that sometimes develops in the body after surgery. When small blood vessels are disrupted, blood plasma can seep out into the surgical area. Further, the inflammatory process can lead to additional fluid exudate. Seromas are different from hematoma (collections of blood), and from abscesses (collections of pus). Seromas can also sometimes be caused by injury, such as when the initial swelling from a blow or fall does not fully subside. The remaining fluid causes a seroma that the body usually gradually absorbs over time (often taking many days or weeks); however, a knot of calcified tissue sometimes remains.
Seromas are particularly common after some plastic surgical procedures where large areas are undermined, leading to large raw surfaces. Seromas are usually preventable by placement of a drain at the time of surgery. However, seromas can develop after the drain is removed. Further, seromas can occur if care is not taken and a patient inadvertently pulls a drain out after surgery. Many patients find that it makes their initial recovery period more difficult, and some need repeated visits to their doctor to have the seroma fluid drained.
Pictured above is about 35 cc of seroma fluid that was drained from a patient following removal of a large lipoma. The patient accidentally pulled out her drain (that was placed during surgery), on the first post-operative night. As a result, the fluid accumulated at the surgical site and required removal with needle aspiration.