Seroma

A seroma is a pocket of clear serous fluid that sometimes develops in the body after surgery. When small blood vessels are ruptured, blood plasma can seep out; inflammation caused by dying injured cells also contributes to the fluid.

Seromas are different from hematomas, which contain red blood cells, and from abscesses, which contain pus and result from an infection. Serous fluid is also different from lymph.

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 serous 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 breast surgery (for example after mastectomy), abdominal surgeries, and reconstructive surgery. They are a treatment target in partial-breast radiation therapy, The larger the surgical intervention, the more likely it is that seromas appear. Larger seromas take longer to resolve than small seromas, and are more likely to undergo secondary infection.