A pressure injury, often called a pressure ulcer or bedsore, is localized damage to the skin and underlying tissue, usually occurring over a bony prominence due to prolonged pressure or pressure combined with shear forces. Healthcare providers use a staging system to classify these injuries based on the depth of tissue damage, ranging from mild redness (Stage 1) to severe wounds (Stage 4). An unstageable classification is used when the full extent of the tissue destruction cannot be visually confirmed because the wound bed is covered by dead tissue.
Criteria for Unstageable Classification
An unstageable pressure injury is defined as full-thickness skin and tissue loss where the true extent of the damage cannot be determined. This lack of visibility is due to the presence of non-viable tissue, specifically slough or eschar, which completely obscures the base of the ulcer. The classification is a temporary designation, reflecting that a Stage 3 (full-thickness skin loss) or Stage 4 (full-thickness tissue loss with exposed structures) injury is present beneath the surface.
Because the full depth is hidden, the injury is presumed to be severe until the non-viable material is removed and the wound bed can be visualized. Clinical guidelines mandate that until sufficient slough or eschar is cleared, the injury must be treated as a deep, full-thickness wound, as the obscured area could involve damage down to the subcutaneous fat, muscle, tendon, or bone.
The only exception to this rule is stable eschar, particularly on a heel or an ischemic limb, which acts as the body’s natural biological cover. Stable eschar is dry, intact, and adherent without surrounding redness or pus, and it should not be removed. In all other instances, the removal of the dead tissue is required to properly stage the wound and guide treatment decisions.
Understanding Slough and Eschar
Slough and eschar are the two distinct types of non-viable tissue that cover a wound bed. Slough is characterized as a moist, softer material that can be yellow, tan, gray, or green, and may appear stringy or gelatinous. This substance is composed of dead cells, fibrin, and wound fluid, indicating an inflammatory response that can slow healing.
Eschar, conversely, is typically dry, hard, and leathery, appearing tan, brown, or black, and is firmly adhered to the wound bed. It represents the end stage of tissue necrosis and desiccation, forming a protective crust over the deeper tissue damage. Slough often requires debridement (removal) to reveal the wound base and promote healing.
The decision to remove eschar depends heavily on its location and condition. Stable eschar on the heel is often left intact because it provides a sterile barrier against infection. Removing this dry, adherent heel eschar could introduce bacteria or disrupt a natural protective layer, especially in individuals with compromised circulation.
How Unstageable Differs from Deep Tissue Injury
Unstageable pressure injuries are frequently confused with Deep Tissue Injuries (DTI) because both involve obscured depth. An unstageable injury is an open wound with full-thickness tissue loss, where the base is obscured by slough or eschar.
In contrast, a Deep Tissue Injury is an area of intact or non-intact skin with localized, persistent discoloration that is deep red, maroon, or purple. DTI represents suspected underlying tissue damage, often appearing like a deep bruise or a blood-filled blister. This discoloration signals tissue damage that originated at the bone-muscle interface, below the surface skin layers.
A Deep Tissue Injury is a warning sign of underlying damage that may evolve rapidly, sometimes revealing a Stage 3 or 4 injury as the skin breaks down. Unlike the unstageable wound, a DTI’s full extent is initially unknown because the superficial layers of skin are still present. Once a DTI opens and the full depth is confirmed to be covered by non-viable material, it may then be re-classified as an unstageable pressure injury.