What Is Seroma?

A seroma is a clinical term used to refer to a localised pooling of serous fluid beneath skin tissue. They typically form as a result of trauma or injury to the tissue and are especially common after a patient undergoes a reconstructive surgical procedure. This article will go over what you need to know about the signs and symptoms, why seromas occur, treatments and prevention. 

Signs and symptoms

Serous fluid is a thin, clear, or pale yellow fluid that fills body cavities, the spaces between tissues or organs in the body. They characteristically contain proteins, electrolytes, and antibodies and can contain small molecules that may have been administered, such as drugs. The type of serous fluid that pools into a seroma is secreted by the cells that form the outer lining membranes of a tissue or organ (serosa). The serous fluid held within this membrane functions as a tissue lubricant and reduces friction, enabling smooth movement against other organs that it may come in contact with. In tissues that have suffered trauma, damaged and dying cells produce serous fluid, which subsequently fills the space or cavities created by the tissue disruption.

Seromas usually develop at, or adjacent to, the site of incision or where tissue has been moved or removed. It presents as a soft lump of varying size, causing tension over the skin. Often, serous fluid can also be seen leaking from the incision or lump. The physical state of the seroma itself also indicates whether or not complications are likely to occur, as reddening of the skin (erythema) and thickening or odorous serous extrusion often point to an infection.

Some seromas resolve themselves without the need for any clinical intervention, or patients can be sent home with a compression bandage to restrict tissue movement. More severe cases, however, require suction drainage or further surgical intervention to remove the fluid and alleviate discomfort from the pressure.¹

Why do seromas occur?

Seromas are most likely to form when ‘dead space’ is created as damaged tissue undergoes recovery from injury. The reconnection of the tissue afterwards is not as effective as a seal before the injury, and this allows for the collection of serous fluid into these pockets of dead space. Patients with a high body mass index (BMI) who suddenly undergo a period of rapid weight loss, for example, are at high risk for developing seromas. 

Surgical procedures such as breast reconstruction and procedures that involve large incisions (abdominal flap detachment or supraumbilical incisions) also frequently result in seromas.² An increased risk of seroma formation correlates with the size of tissue detachment, and therefore, some surgical procedures, such as abdominoplasty, tend to have higher instances of seromas than inguinal hernia repair, for example. Comparatively, seromas arising from inguinal hernia repair are characteristically reabsorbed and resolved unaided.¹

Distinguishing seromas from other conditions

A number of other conditions can also be defined by the pooling of fluid in the body cavities, and these, too, can present in a similar manner to seromas. Some examples are lymphoceles, the build-up of lymphatic fluid; hematomas, the build-up of blood or abscesses, a build-up of white blood cells and dead tissue (pus). A lesser-known condition, Morel-Lavallée lesion, is characterised by the collection of lymphatic fluid and blood within a fibrous capsule, which develops after an initial trauma or injury to the tissue. Its pathophysiology and progression are also very similar to a seroma.³ Given the number of possibilities, it is therefore important to get an early diagnosis of any post-injury or post-surgical swelling to accurately make an identification, treat and avoid the potential development of unwanted complications like scarring or necrosis.

While observation of the fluid drawn by needle aspiration and histological analysis can go some way to positively identifying a suspected seroma, imaging by ultrasound or magnetic resonance imaging (MRI) of the infected area offers a better advantage in being able to distinguish seromas from other soft tissue conditions. Additionally, a computerised tomography (CT) scan is another method for early identification of seromas, as seroma images have specific features and density readings.⁴

Treatment and prevention

Prevention of seromas is always preferable, especially if its likely cause is from a patient undergoing a surgical procedure. It eliminates the need to perform an additional invasive procedure, guards against increased patient discomfort, keeps healing time to a minimum and lowers the risk of developing bacterial infections.

Suction drainage or needle aspiration of fluid from seromas is the most commonly employed method used to reduce fluid accumulation both during and post-surgery. Drains are positioned in the preperitoneal space to remove fluids. This creates a collapse in the dead space and promotes adhesion of the interface to close the wound gap.⁵ Alternatively, seroma aspirations can be done using a 14 gauge needle and syringe, which is introduced into the seroma via the wound line. The system also uses a three-way tap, which allows for the addition of a drainage bag to collect large volumes of aspirate or fluid in a closed system.⁶ However, the apparatus required for both suction drainage and needle aspiration is not particularly ideal as they can create patient discomfort, tissue irritation, premature fluid extrusion due to pressure differentials, and foster bacterial colonisation.⁷

A more effective approach is to minimise the formation of dead space as best as possible by creating a suitably tight seal at the adjoining wound interface. This significantly reduces any shear force experienced by the adjoining surfaces and prevents fluid accumulation or seromas from forming in the first place.²

Fibrin, a bioadhesive glue, which comprises the clotting agent's fibrinogen and thrombin, is a popular choice for closing wounds and is thought effective as it reduces dead space by creating a tensile seal, reduces hematoma (blood pooling) and seroma formation by activating a coagulation cascade and blocking lymphatic drainage into the injury site. 

However, published studies on the use of fibrin glues after mastectomies reported that fibrin is not a particularly effective option for preventing seroma development and that the use of fibrin as a sealant may only be better suited for smaller surgical procedures as opposed to breast reconstruction in particular.^1,8 This suggests that the use of fibrin glue to effectively seal an injury has its limits, and consideration must be given to the nature of the injury and its requirements before choosing fibrin as an option.

Using the quilting suture technique to close wounds has proved to be a significant improvement over using draining techniques for preventing seroma formation.^9,10  Quilting sutures close an operative opening by attaching the skip flap to the underlying musculature, as opposed to suturing on the skin surface. Since the tension is distributed along the subcutaneous length of the skin flap when using quilting sutures instead of the upper cutaneous end of the flap, less shear force is experienced by the adjoining interfaces, allowing the tissue to heal without the formation of seromas.

A systematic review of published literature reporting on seroma prevention reported that, compared with the drainage technique, the use of the quilting suture technique was the preferred option and was significantly better at reducing seroma formation.³

Summary

Seromas are most commonly caused by surgical procedures, especially in reconstructive surgery, where large sections of tissue are removed or sculpted. The disruption and rearrangement of the tissue post-surgery creates a dead space or cavity underneath the skin, which then fills with fluid at or near the incision site. While most seromas will resolve on their own with time, more severe cases can lead to patient discomfort or pain, extended healing times or infection from ineffective management. It is, therefore, preferable to prevent the formation of seromas, and techniques such as quilting sutures, fibrin glues and suction drainage are used during surgical procedures to, as best possible, restrict the creation of dead space so that fluid collection does not occur.