bruise

A bruise, or contusion, is a type of hematoma of tissue in which capillaries and sometimes venules are damaged by trauma, allowing blood to seep, hemorrhage, or extravasate into the surrounding interstitial tissues. Bruises, which do not blanch under pressure, can involve capillaries at the level of skin, subcutaneous tissue, muscle, or bone. Bruises are not to be confused with other similar-looking lesions primarily distinguished by their by their diameter or causation. These lesions include petechia (< 3 mm result from numerous and diverse etiologies such as adverse reactions from medications such as warfarin, straining, asphyxiation, platelet disorders and diseases such as cytomegalovirus), purpura (3 mm to 1 cm, classified as palpable purpura or non-palpable purpura and indicates various patholgic conditions such as thrombocytopenia), and ecchymosis (>1 cm caused blood dissecting through tissue planes and settled in an area remote from the site of trauma or pathology such as periorbital ecchymosis, i.e.,"raccoon eyes" , arising from a basilar skull fracture or from a neuroblastoma).