Pressure Injury Identification & Staging

A wound with visible bone at the base and one with an intact blister over a dark area are separated by multiple stages — but a wound covered in black eschar? You can't stage it at all.

Pressure injuries are staged by the deepest tissue layer visible, not by wound size or appearance of surrounding skin. Stage 1 is intact skin with non-blanchable erythema — press the area and the redness stays. In darker skin tones, look for color changes, temperature differences, or firmness rather than redness. Stage 2 involves partial-thickness skin loss presenting as a shallow open ulcer with a red-pink wound bed, or an intact or ruptured serum-filled blister. No slough or bruising is present. Stage 3 is full-thickness skin loss where subcutaneous fat may be visible, but bone, tendon, and muscle are NOT exposed. Undermining and tunneling may occur. Stage 4 is full-thickness tissue loss with exposed bone, tendon, or muscle. Deep tissue injury (DTI) presents as intact or non-intact skin with a localized area of persistent deep-red, maroon, or purple discoloration, or an epidermal separation revealing a dark wound bed or blood-filled blister. Unstageable injuries have a wound bed obscured by slough (yellow, tan, gray, green, or brown) or eschar (tan, brown, or black) — you cannot determine the stage until enough debris is removed to visualize the base. Critical rule: pressure injuries are never reverse-staged. A healing Stage 4 does not become a Stage 3. Document it as a 'healing Stage 4.'

Key Distinctions

Don't confuse Stage 2 (partial-thickness, no slough) with a moisture-associated skin injury — Stage 2 occurs over bony prominences, moisture damage follows skin folds and perineal areas. Students mistake DTI for Stage 1; DTI is deeper, darker (maroon/purple), and often evolves rapidly. Unstageable does not mean 'worst stage' — it means you literally cannot see what's underneath.

Clinical Pearl

If you can't see the bottom, you can't call the stage. Eschar and slough hide the truth — document it as unstageable until debridement reveals the wound bed.