Editor's note: This blog was originally published in November 2011. It was revised and republished in April 2021.

Introduction

As health care professionals monitor the wound drainage of a patient, it is critical to be able to recognize the different types of wound drainage. Open wounds and incision wounds may both present varying types of exudate, some of which are perfectly healthy and others that can signal an infection or slow healing. Identifying wounds that need a change in care can speed the healing process. Here are the four main types of wound drainage health care professionals need to know:

Sanguineous Wound Drainage

Sanguineous wound drainage is the fresh bloody exudate that appears when skin is breached, whether from surgery, injury, or other cause. Sanguineous drainage is bright red and somewhat thick in consistency; some compare it to the consistency of syrup. It can be seen during angiogenesis in both full-thickness wounds and deep partial-thickness wounds. This type of drainage is a normal part of the inflammatory phase of wound healing, but it should lessen considerably over time and stop after a few hours in most instances.¹

In some deeper wounds, sanguineous wound drainage may continue for a few days but should distinctly lessen in volume. This drainage has the features of added plasma, which makes the run-off appear pink. Sanguineous wound drainage that continues unabated, saturates bandages in a few hours, or reappears when it has stopped can be a sign of a problem in wound healing. There may be fresh trauma to the wound site, the patient may be too active after surgery, or there may be some kind of stress on the wound site that needs inspection.

Serous Wound Drainage

Serous drainage is mostly clear or slightly yellow thin plasma that is just a bit thicker than water. It can be seen in venous ulceration and also in partial-thickness wounds. Generally, this is not one of the types of wound drainage that leaves much color on a bandage. Serous fluid contains sugars, white cells, proteins, and other chemicals that are vital in the healing process to move across the wound site. Therefore, serous is one of the normal types of wound drainage and often appears in the first 48 to 72 hours.¹

Sometimes, thin, watery drainage appears that is tinged with pink from a small number of red blood cells. In the early stages of healing, this pink serous wound exudate is normal and is not necessarily an indication of either infection or slow healing. Frequently, serous wound drainage may make a bandage wet, but it should not become increasingly heavy or regularly soak through dressings because this can indicate an increase in bioburden or the presence of potentially harmful bacteria. Additionally, if large amounts of serous drainage appear on an incision line, or if the fluid weeps from the skin in areas where there is no trauma, that can be a sign of a medical condition, such as severe pitting edema. Patients with all excessive types of wound drainage should be carefully monitored for signs of infection or health problems.

Seropurulent Wound Drainage

Wound drainage that turns cloudy, yellow, or tan is called seropurulent and is usually a sign that the wound is becoming colonized and treatment changes are needed.¹ Seropurulent wound drainage can have a variety of colors, including pink, gray, yellow, tan, brown, green, or white. Color alone is not necessarily an indicator of wound infection, but any change from clear drainage should be noted and examined.

Purulent Wound Drainage

Purulent drainage is not a characteristic of normal healthy wound healing. Exudate that becomes a thick, milky liquid or a thick liquid that turns yellow, tan, gray, green, or brown is almost always a sign that infection is present.¹ This drainage contains white blood cells, dead bacteria, wound debris, and inflammatory cells. Purulent wound drainage is commonly called "pus" and often has a foul or unpleasant smell. Additionally, it can increase an inflammatory response, resulting in intense pain at the wound site and surrounding skin. Wound drainage with a foul odor in and of itself does not indicate infection. All wound drainage contains bacteria that feed off byproducts in the drainage, and this activity produces an odor.

Conclusion

In determining the progress of wound healing, medical professionals should examine the types of wound drainage for color, clarity, thickness, and odor. Those qualities, along with the quantity of drainage and the expectation that drainage will continue to progress toward being clearer with less volume as the wound heals, can help health care professionals to determine the need for interventions in wound care.

Reference

1. Swezey L. Wound assessment - wound drainage and odor. WoundEducators.com. 2014. https://woundeducators.com/wound-drainage-and-odor/ Accessed October 24, 2019.