A seroma is a collection of serum (also known as lymph fluid) within a cavity inside the body. Serum is the yellowish liquid portion of blood that remains after the red blood cells (which transport oxygen to the body's tissues), and white blood cells (which fight infections) have been removed.
Serous fluid (serum) is the pale yellow straw coloured fluid that is produced by lymph vessels and by the tissues that lie beneath the skin. You'll have seen serous fluid if you've ever had a blister on your hand or foot - the fluid that comes out when you puncture a blister is serous fluid.
A seroma then, is just fluid, serum that has accumulated in a dead space in the tissue. It is the result of tissue insult (trauma) and the product of tissue inflammation and the body's defense mechanisms. The body is simply reacting to the presence of a dead space within the tissue that was previously attached to something. When we remove a large mass, or create a defect (such as making the subcutaneous pocket needed for a DSI transmitter body), we damage the very small vessels that previously ran from the underlying tissue (i.e., muscle, connective tissue) to the overlying tissue (i.e., skin, muscle). Although these vessels do not cause significant blood loss, they do allow escape of serum into the area. There is also the resulting tissue damage that occurs regardless of how carefully a surgeon operates. This tissue damage results in cellular death. The body's reaction is an inflammatory one. Because of the inflammation, cell death, and increased vascular permeability, fluid can accumulate in the newly created space. This process will generally resolve over time if there is some form of natural drainage, if there is not continued irritation to the area, if circulation to the area is sufficient, and if the patient is in good health.
In general, the hallmark of treating seromas consists of insertion of a drain (to maintain the evacuation of any fluid), compression (when possible) and, if necessary, removal of the foreign body. If a procedure is required after the seroma has been in place for a while (ie, several months) then, in addition to removing the foreign body, it is probably necessary to remove the scar tissue that typically forms around long-standing fluid collections (and which then starts contributing to the fluid formation). This tissue is called a pseudobursa.
However, there are reports of seromas after a number of intrusive surgical procedures including and is commonly associated with “tummy-tucks,” liposuction, and other plastic surgery procedures or other trauma.