PLEASE NOTE A NEW 4TH EDITION HAS BEEN PUBLISHED AND IS AVAILABLE IN THE LIBRARY AND IN PRINT

An erosion is a circumscribed depressed lesion that represents a defect of the epidermis that does not penetrate the basement membrane. Erosions do not bleed and they heal without scarring. An ulcer is a deeper defect that extends into the dermis after disruption of the basement membrane. These lesions are frequently covered by crusts, they bleed easily and, at least when they involve deep dermis, they heal with the formation of a visible scar. Ideally, the differentiation between erosions and ulcers should be based on histopathology, because it may be impossible to differentiate deeper erosions from shallow ulcers during clinical examination. Nevertheless, this distinction may not be particularly helpful in the diagnostic process because the canine and feline epidermis is thin, and therefore erosions frequently evolve into ulcers, especially if they become infected or self-traumatized. Erosions and ulcers are therefore discussed collectively for the remainder of this chapter, although more severe or deeper pathological processes are generally responsible for ulcer formation. The chapter focuses on Pathophysiology; Differential diagnosis; and Clinical approach.