A seroma is a common and usually temporary complication where sterile, clear fluid collects beneath the skin’s surface following surgery or significant trauma. This fluid is a mixture of blood plasma and lymphatic fluid leaking from damaged vessels. Seromas cause localized swelling and may develop in the days or weeks following an operation.
Visual and Tactile Characteristics
The most noticeable sign of a seroma is a localized swelling or lump beneath the skin near a surgical incision. This swelling can range from a subtle bump to a large protuberance, often appearing 7 to 10 days after surgery or after surgical drains have been removed.
When touched, a seroma typically feels soft, elastic, and spongy, often described as feeling like a water balloon. If the fluid collection is large or under tension, the lump may feel firmer and more taut. Gently pressing on one side may reveal fluid movement within the pocket.
The skin covering the seroma usually retains its normal color, or it may appear slightly pink or red due to localized inflammation. This helps distinguish a seroma from a hematoma (characterized by bruising) or an abscess (involving significant redness and warmth). If the seroma fluid were to be drained, it would appear clear or a pale, straw-yellow color.
Context: Common Locations and Underlying Cause
Seromas form primarily due to the creation of a “dead space” where tissue has been removed or separated from underlying structures. When an incision is closed, tissue layers sometimes fail to reattach immediately, leaving a small cavity. This space fills with fluid because surgical trauma disrupts small blood vessels and lymphatic channels.
The resulting leakage of plasma and lymph into this cavity is the mechanism of seroma formation. This complication is frequently observed following procedures that involve extensive soft tissue dissection. Common sites include beneath skin flaps during abdominoplasty and the chest wall after mastectomy or breast reconstruction.
Seromas are also common after hernia repair, especially open incisional hernia repair, and procedures involving lymph node dissection. The extent of the surgery and the amount of tissue disruption directly influence the likelihood of a seroma forming. Up to 85% of people who undergo mastectomy may experience a seroma.
When and How Seromas Are Treated
Many small seromas resolve on their own, with the body gradually reabsorbing the fluid over a few weeks to several months. Medical intervention is generally reserved for seromas that are large, symptomatic, or fail to diminish. Wearing compression garments can help reduce fluid buildup in minor cases.
For larger collections, the standard treatment involves needle aspiration (paracentesis), where a fine needle is used to draw the fluid out. This procedure may need to be repeated multiple times until the seroma stops refilling. In some cases, a temporary surgical drain may be placed to continuously remove the fluid.
It is important to monitor the seroma for signs of infection, which requires immediate medical attention. Signs that a seroma may be complicated include increasing pain, rapid growth, spreading redness or warmth over the lump, or the presence of fever. If the fluid discharge becomes cloudy, bloody, or develops an odor, it may indicate that the seroma has become infected and is developing into an abscess.