A. Photograph of the large abdominal bruise (8.5 × 13 cm) that formed at 48 hours in one dog. B. Electron micrograph from the dog in A after 24 hours of thrombocytopenia, 24 hours prior to the development of the bruise. A large gap between adjacent endothelial cells is marked with an arrow. RBCs are shown in lumen; x 20,000. C. Pale, swollen endothelial cells consistent with necrotic cells and inter-endothelial cell gaps (arrows) present in an electron micrograph from the bruised region of another dog that developed an ecchymosis; x 20,000. D. For comparison, normal closely apposed adjacent endothelial cells connected by an intact junction (arrow) in a dog at baseline are shown; x 20,000.