Types of Drainage from Wounds that Providers Should Know

Identifying the type of wound a patient has is very important, as it allows you to develop a treatment plan. But identifying the types of drainage from the wound is equally significant. Some drainage is normal, signifying that it’s a healthy, healing wound, but others could suggest the presence of infection. 

Below, we will explore the different types of drainage from wounds that clinicians should be aware of and offer suggestions for achieving the best outcome for their patients. 

What Is Wound Drainage?  

While other specialties and general practitioners are more likely to call it wound drainage, wound care experts likely refer to it as exudate. The term exudate comes from the word exude, which means “to ooze.” 

Exudate consists of water, protein, white blood cells, fluids, electrolytes, enzymes, inflammatory mediators, and other cellular substances. It comes from the fluid that seeps from blood vessels and enters nearby soft tissues and wounds. 

Understanding How Wound Drainage Happens

Before we explain the four types of wound drainage, let’s begin by looking at how exudate comes about. 

Our circulatory system has capillaries, or small blood vessels, where blood flow takes place. Some fluid, resembling blood plasma, leaks into the body tissue as this occurs. The rate of leakage into nearby tissue varies but is based mainly on the hydrostatic and osmotic pressures across the capillary walls and capillary permeability. According to research, approximately 90% of the leaked fluid is reabsorbed into the capillaries, while the remaining portion returns to central circulation via the lymphatic system. All of this is how the process functions normally.  

When a wound occurs, though, the capillary permeability increases, allowing white blood cells, or leukocytes, to escape. During this process, the blood vessels dilate and leak additional fluid, which creates the basis of exudate. 

Is Wound Drainage a Bad Thing? 

Exudate often gets a bad rap, but it’s crucial to clarify that this fluid is an essential part of the normal wound healing process. In fact, it presents itself early on, and in increased amounts during the inflammatory stage to offer a moist wound environment. Wound drainage supplies dermal cells and a host of essential nutrients for healing. Exudate may also be seen during the proliferative stage, aiding with the transfer of tissue-repairing cells throughout the wound bed. 

At the inflammatory stage, wound fluid usually has a higher viscosity, meaning it is thicker and more resistant to flow. The exudate’s thick consistency results from its high protein content, with research suggesting more than 30 grams per liter. Usually, the more white blood cells, proteins, and bacteria there are, the thicker the fluid. 

However, high viscosity could also indicate a bacterial infection, so it’s important to pay attention to other factors, like the fluid’s color and odor. While exudate itself is not meant to be damaging, it really depends on the types of drainage from the wound. 

Types of Drainage from Wounds

According to the National Library of Medicine, there are four types of wound drainage that providers should look for and document. So what are the 4 types of wound drainage? Don’t worry, we’ve got you covered. Those four primary types are sanguineous, serous, serosanguinous, or purulent. Keep reading for a closer look at each.

Sanguineous Wound Drainage

When you see fresh blood coming from an open wound, this is likely sanguineous drainage. It’s a standard reaction to an injury, whether that injury is intentional, from surgery, or something like a laceration. This form of exudate is most often seen in partial-thickness or full-thickness wounds, which are sometimes associated with blood vessel damage. 

Sanguineous drainage is expected during the inflammatory stage, especially when new blood vessels are developing. 

Potential Concerns and Challenges

If you see this exudate during later stages, something might be wrong. Often, it indicates that the wound has reopened, the patient is very active, or the patient has experienced some sort of trauma or stress. 

Another cause of concern is excessive sanguineous drainage or a lack of decrease in production as the patient transitions out of the inflammatory stage. Determining what’s excessive can be tricky, as it partially depends on the size of the tissue damage and whether the patient is dealing with other complications. 

For instance, patients with deeper wounds might experience this form of drainage for a few days, but after that, it should be clear that exudate production is starting to decline. 

Pay close attention to the wound’s overall appearance and any additional symptoms to determine if there’s an issue. If the bandage has become saturated after just two to three hours, it’s time to take a different treatment approach. This could be a sign of hemorrhage. If drainage stops and then suddenly restarts, this could be an early sign of an infection. 

Issues are more likely if a patient has blood flow challenges, such as those seen in patients with diabetes or renal failure. Poor vascular health compromises wound healing, as wounds require an adequate blood supply. 

The Appearance and Odor of Sanguineous Drainage 

Because it’s mainly made up of fresh blood, you’ll find that sanguineous drainage has a bright red appearance. However, the color turns deep red when it starts to clot. It also typically has a thin, watery consistency and an iron-like smell. In some cases, it may not have an odor at all. 

Serous Wound Drainage

Like sanguineous wound drainage, the presence of serous exudate during the healing process is also normal. In fact, seeing this fluid indicates that your wound is on the path to healing. It’s appropriate to observe small amounts during the inflammatory phase. 

According to the Cleveland Clinic, serous drainage is plasma without protein. It is considered one of the most common exudate forms and is usually seen in post-operative incisions, partial-thickness wounds, open sores, or venous ulcerations. Patients with significant swelling under the skin are more likely to see this type of drainage. 

Potential Concerns and Challenges

Scant amounts of serous fluid are normal, but if there’s an increase in production, it could be an infection. It’s not typical for this exudate to continuously soak through dressings, so if that occurs, there may be a boost in bioburden, meaning there’s a growth of bacteria living on the surface of the wound that hasn’t been sterilized.  

If you’re assessing a patient and notice serous fluid weeping from uninjured skin or copious amounts coming from a wound incision line, it might be a sign of severe pitting edema. 

The Appearance and Odor of Serous Drainage

This form of exudate is usually clear or pale yellow, so if you remove a patient’s bandage, you might not see much color there. Serous drainage has a thin, almost water-like consistency. Around the wound, you might even notice the clumping of fibrin, a protein needed to form blood clots. 

Serosanguinous Wound Drainage

Another form of normal wound drainage, serosanguinous exudate, combines the two aforementioned fluids. This type includes serous fluid and small amounts of red blood cells. Wound care providers might notice this discharge at an incision site after surgery or oozing from some other form of wound. 

Serosanguinous fluid ordinarily appears during the inflammatory stage, indicating damaged capillaries. It doesn’t indicate a serious problem in small amounts and is a sign of a healthy, healing wound. 

Potential Concerns and Challenges

There are a few possibilities if you notice excessive quantities of serosanguineous drainage while completing a wound assessment. 

Sometimes, this exudate is found in chronic wounds, which alerts you that the wound is having trouble moving past the inflammatory stage. To help the wound move along the healing journey, double-check the type of wound dressing being used and the frequency of dressing changes. Ask yourself if it provides adequate absorption—and if the answer is no, the wound isn’t in the proper environment for healing. You want to avoid having the fluid just sit on top of the wound surface, as it can lead to skin maceration and additional tissue damage. 

In some cases, the patient might require a negative pressure wound vacuum to get healing on the right track. Sometimes, serosanguinous drainage is present in large amounts in patients with certain comorbidities. This is why it’s essential to examine the whole patient, not just the wound. 

The Appearance and Odor of Serosanguinous Drainage

This form of exudate can vary in color, so it might look slightly yellow, light pink, or light red. The more capillaries that were injured, the more tinges of pink you’ll probably see. You might even notice some blood streaks or clots, but this should subside and become colorless as the patient moves through healing. 

Serosanguinous exudate has a thinner consistency because it’s mainly water. Typically, it doesn’t have an odor. However, if you do notice a foul smell, assess whether the dressing is properly in place and absorbing the drainage. 

Purulent Wound Drainage

Unlike the others, purulent drainage​​, also known as pus, is a sign of a problem. As the National Institute of Health states, “It is never considered normal in a wound bed,” as it’s a symptom of infection. This type of drainage consists of bacteria and dead cells, but there’s the presence of leukocytes, too. The latter are sent to destroy the pathogens and clear debris.

When the germs infiltrate the protective layer of the wound and get inside the skin, they start to multiply and trigger an infection. Wound contamination can come about for several reasons, but it often originates from: 

• The environment. Examples of environmental causes would be an exogenous microorganism in the air or an object introduced during the injury, such as a nail or poorly sterilized surgical instrument. 
• Surrounding skin. The skin’s diverse microflora provides an environment for controlled bacterial growth, but other factors, such as age, genetics, and more, could make patients more vulnerable. 
• Endogenous sources. Microorganisms from the patients’ mucous membranes, such as the gastrointestinal or oropharyngeal mucosa, could invade the wound area. 

Potential Concerns and Challenges

Some risk factors make a patient more likely to develop wound infections, such as diabetes, malnutrition, obesity, smoking, and age – just to name a few. As a result, if a patient presents with an acute wound and has those risk factors, it’s crucial to closely monitor their progress. After all, it’s not unlikely that an acute wound with purulent drainage will become chronic later without adequate treatment. Plus, if the wound remains stuck in the inflammatory phase and becomes difficult to control, it puts the patient at risk of amputation. 

Also keep in mind that challenging-to-treat wounds, like diabetic ulcers and pressure injuries, are more likely to contain purulent exudate. 

Injuries with purulent drainage require an urgent response, as the infection can spread. The best course of action for wound infections is to obtain a culture as quickly as possible. That’ll help you determine the cause and initiate proper antibiotic therapy. Selecting the best wound dressing for maintaining the exudate is also necessary. Failure to do so will hinder healing, even with antibiotic treatment, because of the risk of tissue maceration. 

The Appearance and Odor of Purulent Drainage

It’s hard not to notice purulent exudate due to its green, yellow, brown, gray, white, or pink color. Purulent is thick and milky unlike the thinner consistency found with other drainage forms. Clinicians might also notice a poor odor coming from the wound site, alerting others that there’s an issue. 

In addition to the above, patients experiencing purulent drainage might notice the following:

• Pain and tenderness at the wound site
• Redness 
• Feverish 
• Swollen lymph nodes 
• Swelling around the wound 
• Feeling unwell 

The Different Types of Drainage from Wounds Revealed

Many wound care clinicians are very familiar with the primary forms of exudate and can easily answer questions like, “What are the four types of wound drainage?”. However, refreshers like this can be beneficial even for the most experienced providers, as we all have moments of uncertainty. Therefore, feel free to use this, along with observing various types of wound drainage pictures, to help you make the most informed decisions for your patients.