A seroma is a collection of fluid that builds up under the surface of the skin. It may develop after a surgical procedure, most often at the site of the surgical incision or where the tissue was removed.

The buildup of fluids under the skin, called seroma, is a common complication of surgery.

Experts suggest that up to 85% of people who undergo mastectomy surgery for breast cancer experience some type of seroma. After hernia surgery, 5.4% may experience a seroma from laparoscopic hernia repair, and 12.5% after open incisional hernia repair.

The fluid (serum) is a mixture of lymphatic fluid and plasma, the liquid part of blood. Serum builds up in the empty space beneath the skin where you received an incision. It may take several weeks after surgery for serum and swelling to appear.

In many cases, small seromas can get better on their own without treatment. Sometimes, however, a seroma may require medical intervention.

Keep reading to learn more about the causes, symptoms, and treatments for seromas.

A seroma most commonly forms within 7 to 10 days after a surgical procedure.

The removal or disruption of soft tissue is a type of surgical trauma that can damage tissue, vascular, and lymphatic drainage vessels, leading to a buildup of fluid and inflammation.

In some cases, a seroma may form after minor surgery, but it usually appears after an extensive procedure, such as breast mastectomy and hernia surgery. Seromas are the most common complication of breast cancer surgery.

According to the American Board of Cosmetic Surgery (ABCS), the following types of cosmetic surgery may result in seromas:

Your surgical team will place drainage tubes in and around the incision to try to prevent a seroma. The drainage tubes may remain in your body for a few hours or a few days after the surgery in order to prevent fluid buildup.

In many cases, the use of drainage tubes will be sufficient to prevent a seroma. However, that’s not always the case, and a week or two after the procedure, you may begin noticing the signs of fluid buildup near the incision.

In many cases, a seroma will appear like a swollen lump or large cyst. It may also be tender or sore when touched, and you may experience clear discharge from the surgical incision when a seroma is present.

If you think you may have a seroma, the ABCS recommends gently pressing one side of the bump. A fluid movement, like liquid in a bag, may indicate the presence of a seroma.

If the discharge becomes bloody, changes color, or develops an odor, you may have an infection. It’s important to get medical attention if this occurs to prevent any complications of infection.

In rare cases, a seroma may calcify. This will leave a hard knot in the seroma site.

Researchers have identified several risk factors that may increase your risk of developing a seroma after a surgical procedure. These may include:

  • having extensive surgery, such as a procedure that disrupts large amounts of tissue
  • having a history of seromas following surgical procedures
  • having an underlying health condition, such as diabetes, obesity, or hypertension (high blood pressure)
  • taking anticoagulants (blood thinners)
  • being over age 40 years

Some of these risk factors may affect your body’s natural wound-healing processes or increase inflammation.

In most cases, a seroma will heal on its own because your body may naturally reabsorb the fluid in a few weeks or months. Taking over-the-counter (OTC) medications like ibuprofen may help relieve pain, discomfort, and inflammation.

Larger seromas may require treatment by your doctor.

The most common treatment is fluid aspiration to drain the seroma. A doctor inserts a needle into the seroma and removes the fluid with a syringe.

Seromas may return, and your doctor may need to drain a seroma multiple times. In some cases, your doctor may suggest removing the seroma entirely, which is accomplished with a minor surgical procedure.

Sometimes, a seroma may cause discomfort or limit your range of motion. But the biggest complication associated with seroma is infection, which may develop within 3 months of your operation.

A seroma may drain externally onto your skin’s surface from time to time. The drainage should be clear or slightly bloody. If you begin experiencing the symptoms of an infection, the seroma may have developed into an abscess.

An abscess requires medical treatment like drainage or antibiotics. If left untreated, it may grow in size, and the infection can also make you sick, especially if it spreads to the bloodstream. This increases your risk of developing a severe illness or sepsis.

When to seek emergency medical help

Serious or long-term problems related to a seroma are very rare. However, seek emergency medical attention if you experience any of the following symptoms:

A seroma will usually go away on its own within a few months. In some cases, however, a seroma may require medical intervention to drain it, especially if you have an infection.

If left untreated, a seroma may become infected. This could cause discolored pus to discharge from the seroma, as well as symptoms like fever, chills, and confusion. It’s important to get medical attention if you experience discolored drainage to prevent further complications.

A seroma will usually drain on its own. It’s important not to intentionally open the seroma or try to drain it yourself, as this may increase the risk of infection.

Lymph drainage is a type of massage that may be helpful for seromas because they have lymph fluid. That said, it should be done cautiously and preferably by a healthcare professional trained in lymphatic drainage techniques.

More research is needed to understand the effects of massage on seroma.

A seroma is a buildup of fluid beneath the skin that most commonly occurs after operations.

Sometimes, surgical drainage systems are used in some surgeries to help prevent a seroma from developing. Wearing compression garments may also help skin and tissue heal faster after surgery and reduce swelling and bruising.

If you experience a seroma that gets bigger, more painful, or shows signs of infection, speak with a healthcare professional. They could recommend a treatment plan to reduce the risk of complications.