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Assessing Wound Tissue and Drainage Types: Slough Versus Purulence

Editor's Note: This blog was originally published in April of 2019. It was revised and republished in February 2021.

Wound assessment is one of the initial steps in determining the plan of care, changes in treatment, and the choice of key players in wound management. However, wound assessment needs to be accurately understood and documented by frontline staff to paint a true picture of what is happening with the wound.

Tissue Type: Slough

We've all heard about slough… most of us have seen it, debrided it, and even watched it change from wet (stringy, moist, yellow) to dry eschar (thick, leathery, black). Slough is necrotic tissue that needs to be removed from the wound for healing to take place. When referring to slough, some terms may be used interchangeably, fibrotic tissue or necrotic tissue most commonly. It is important to differentiate between wet necrotic tissue and dry necrotic tissue to formulate the best, evidenced-based wound care treatment plan.

As wound care clinicians, when we see slough, we want to get rid of it so that the wound is able to heal because necrotic tissue prevents or slows healing. So we refer to our wound care "tool box" and develop the best plan of attack:

  • Sharp debridement (bedside)
  • Debridement with the patient under anesthesia (operating room)
  • Autolytic debridement
  • Chemical or enzymatic debridement
  • Mechanical debridement
  • Biological debridement

Once we initiate our plan of care (usually from the choices listed above), debridement will begin to occur or will occur at the point of treatment (with sharp debridement in the operating room or at the bedside, if appropriate). As debridement is implemented, the slough liquefies or dissolves and is (sometimes slowly) removed from the wound bed. However, as slough liquefies, the drainage may be confused with purulent drainage, depending on the nurse's assessment and experience. Additionally, as we know, wound drainage has an odor most of the time. That is why we do not document odor until after we have removed the old dressing, disposed of it, and cleansed the wound. If there is still an odor after completing those steps, then it is appropriate to document the presence of malodor.

Purulence and Infection

Is the drainage liquefied slough or truly purulence? Purulence—which means the presence of pus—and infection may go hand in hand in a wound, so what are the signs and symptoms of infection?

  • Erythema
  • Odor
  • Redness that does not improve with elevation in a limb (not dependent rubor)
  • Pain
  • Increase in drainage (color: green or blue, etc.)
  • Fever, chills, nausea, vomiting (systemic)

Does your patient have signs or symptoms of infection, along with purulence? Or are you simply wiping away the slough that has liquefied as our debriding agent does its job? Remember to look at the big picture, examine the periwound, compare assessments and documentation from past to present, and ask for someone else to lay eyes on your assessment if you're questioning it. Additionally, always rely on your wound care specialists—that is what we are here for! Understanding and accurately documenting tissue types are critical parts of wound assessment that truly guide treatment and intervention. Here are some additional tips for when you're not sure of what you see or what to document:

  • Always cleanse the wound before documenting odor.
  • If you're not sure what it is, don't document it yet— check first (keep in mind that slough can be confused with purulence, tendon, or other underlying structures).
  • If something doesn't look right to you, it probably isn't—trust yourself, and notify appropriate team members.
  • If what you're cleansing out of the wound is stringy and yellow, and the wound base appears more granular after cleansing, it is most likely slough.
  • If there is an odor, erythema, and signs and symptoms of infection, you're most likely dealing with purulence or purulent drainage.

Additional Important Takeaway Points
Anytime you have a stable eschar on a heel (no fluctuance, purulence, odor, etc.), do not unroof or debride it, and involve podiatry and/or vascular specialists. Keep the wound dry and stable, offload the area as much as possible, and gather input from your consulting services.

You will not see slough in a stage 2 pressure injury. Slough is present only in stage 3 pressure injuries and higher. Slough may be present in other types of wounds such as vascular, diabetic, among others.

You are most likely not seeing a biofilm. Biofilms may be present, especially in chronic wounds, but they are usually not visible to the naked eye.


So, remember always to involve a specialist, especially if you're questioning yourself. Trust your gut, and don't document yet if you’re not sure what you're seeing—ask first! Additionally, keep in mind the key differences between infection and slough, as discussed here. A wound typically cannot heal if either infection or slough is present, but the treatment plan for each is very different. Taking a multidisciplinary approach and managing the entire patient are critical to wound healing. Accurate documentation is essential in painting a picture of that wound for different team members who may be reviewing the medical record to determine their plan of care. Always ask—there's something new to learn every day!

About the Author
Holly is a board-certified gerontological nurse and advanced practice wound, ostomy, and continence nurse coordinator at The Department of Veterans Affairs Medical Center in Cleveland, Ohio. She has a passion for education, teaching, and our veterans. Holly has been practicing in WOC nursing for approximately six years. She has much experience with the long-term care population and chronic wounds as well as pressure injuries, diabetic ulcers, venous and arterial wounds, surgical wounds, radiation dermatitis, and wounds requiring advanced wound therapy for healing. Holly enjoys teaching new nurses about wound care and, most importantly, pressure injury prevention. She enjoys working with each patient to come up with an individualized plan of care based on their needs and overall medical situation. She values the importance of taking an interprofessional approach with wound care and prevention overall, and involves each member of the health care team as much as possible. She also values the significance of the support of leadership within her facility and the overall impact of great teamwork for positive outcomes.

The views and opinions expressed in this blog are solely those of the author, and do not represent the views of WoundSource, HMP Global, its affiliates, or subsidiary companies.