Full thickness tissue loss in which the base of the ulcer is covered by slough (yellow, tan, gray, green or brown) and/or eschar (tan, brown or black) in the wound bed.

Pressure ulcers are often difficult to diagnose, there has been confusion particularly between pressure ulcers and a wound caused by moisture. It is critical to correctly diagnose as both prevention and treatment programmes may differ2.

Key characteristics to be aware of (adapted from EPUAP statement)2

 Moisture should be present, for example incontinence.
A wound located on a bony prominence is most likely to be a PU, however, this is not an exclusive statement. Moisture lesions can occur on a bony prominence but ensure that pressure and shear have been excluded as causes, and moisture is present.
Surrounding skin that presents with pink/white spots usually points to maceration.
While PU tend to be singular and regular in shape moisture lesions tend to be diffuse with multiple spots and irregular in shape.
Moisture lesions are usually superficial.
If necrosis is present it is unlikely to be a moisture lesions.