What is a seroma?
No wound, no seroma: A seroma is an accumulation of wound fluid that penetrates into body tissue and fills a self-generated cavity. As a result of this displacement, the tissue swells.
Seromas differ from other formations in which there is also an unwanted accumulation of fluid:
- Hematoma: This is a collection of blood in the tissue following an injury and is also known colloquially as a bruise or “bruise”.
- Abscess: This occurs during an inflammation when a pus-filled cavity forms.
- Empyema: This is an accumulation of pus in a pre-existing cavity.
- Cyst: This is a fluid-filled cavity lined with a specific cell layer (an epithelium). Cysts develop independently of wounds.
As fluid also accumulates in a cavity in a seroma and this formation resembles a cyst, seromas are sometimes also called “pseudocysts”.
The odorless liquid of the seroma is colorless or slightly yellowish in color. This may be wound secretion (exudate) – a wound fluid that the body filters out of the blood. Or the fluid consists of blood serum, i.e. the liquid part of the blood, without red and white blood cells or other solid components. A third possibility is that the fluid in the seroma is lymph, or lymphatic fluid.
More about the lymphatic system and possible disorders
Symptoms: How do seromas manifest themselves?
Small seromas can develop completely unnoticed and also dissolve again after some time without the affected person noticing. This applies in particular to small seromas in deeper regions of the body.
However, a seroma often forms in the soft areas near the surface of the skin. Here it appears as a clearly visible swelling or bump under the skin. It can be perceived as a visual blemish, cause feelings of emotional shame and restrict the quality of life. Although the actual swelling of the seroma is not sensitive to pressure, seromas can cause unpleasant feelings of tension and pain in the surrounding tissue. They also often lead to restrictions in freedom of movement.
Seromas are often associated with impaired wound healing. As the fluid contained in a seroma can become a breeding ground for pathogens, inflammation (infection) can easily form in the wound. Typical signs are reddened skin and fever. If the infection lasts longer, pus may form. It is also possible for wound fluid to leak out of the wound. This secretion is called secretion.
Causes: Why do seromas develop?
Seromas often occur as a side effect of surgery. They are one of the most common complications following the removal of lymph nodes as part of cancer treatment.
Seromas after surgical procedures
Lymph vessels: A further risk of seroma arises from the surgical removal of lymph vessels, for example in the armpit. In other operations, lymph vessels may be injured unintentionally. As a result, the lymph fluid can no longer drain away in the normal way, but accumulates and creates a seroma.
Seromas: What promotes their development?
It is usually not possible to determine why a seroma is formed (or not) in a specific individual case. The causes are rarely clearly identifiable. However, various studies and field reports have identified a number of factors that could favor seroma formation:
- Irritation or foreign bodies in the area of the wound
- Infections of the wound
- Wide incisions in the abdominal skin during surgery
- Stitches removed too early after the operation
- Injuries and impacts
- Lymphatic drainage disorders
- A larger number of removed lymph nodes
- Severing of lymphatic vessels
- Previous radiation
- Large tumor
- Large implant (for breast reconstruction)
- Smoking
- Metabolic diseases
- Diabetes
- Obesity
Diagnosis: How do you recognize a seroma?
Most seromas form under the surface of the skin. Here they become visible as a swelling that does not change color – this distinguishes them from a bruise (hematoma).
Deeper seromas are usually not palpable. In this case, sonography, i.e. an examination using ultrasound, helps with the diagnosis. This requires a great deal of experience: Ultrasound images often make it difficult to distinguish whether a visible swelling is a seroma, a hematoma or a tumor.
If imaging does not provide a clear diagnosis, a puncture can provide information: The wound is punctured with a hollow needle, through which wound fluid flows out and can then be examined.
Therapy: How are seromas treated?
In order for a seroma to regress as quickly as possible, it must be relieved and freed from the fluid it contains. This is usually done by aspirating (“puncturing”) the wound secretion. The opening created by the puncture is then closed with a pressure bandage. It should also prevent the emptied cavity from filling up with liquid again.
Drainage for the wound fluid
Drainage is often used in the event of renewed fluid formation or larger wounds: After the wound has been punctured interventional, the wound fluid flows through a thin tube into a container. This is usually combined with sclerotherapy to obliterate the wound cavity. The treatment can be lengthy.
Drainage has the advantage over puncture that the wound secretion can drain away steadily and over a longer period of time. Ideally, the deflated wound is pulled together so that its edges converge and grow together. This closes the wound and allows it to heal.
Treating seromas microsurgically
Some seromas have to be treated surgically – especially if the formation of new fluid cannot be prevented in any other way. The hospital’s surgical team also needs a great deal of experience in this area: for example, severed lymph vessels that are so fine that they have to be treated under a microscope are detected during the operation. They are often connected to each other or to small veins so that the lymphatic fluid can drain away again unhindered.
After the operation, a pressure bandage can support the healing process. To prevent the fresh wound from becoming irritated and possibly opening up, doctors usually advise those affected to move carefully and little for a while.
Preventive reconstruction of the lymphatic drainage system
A new method to reduce seroma after surgery and to reduce the development of lymphedema is to reconstruct the lymphatic drainage at the end of an operation directly by microsurgery. This is particularly useful if many lymph nodes have been removed and a correspondingly large number of lymph vessels have had to be cut, e.g. in the armpit during treatment for breast cancer or in the groin after treatment for malignant melanoma.
Progression: How do seromas develop?
A seroma usually develops around seven to ten days after an operation. In some cases, smaller seromas disappear on their own. However, this is only possible if no new fluid is produced and if the body tissue gradually takes up (absorbs) the existing fluid. Such healing without medical support can take several weeks or even a quarter of a year.