This is an example of pseudomembranous enterocolitis. The mucosal surface of the colon seen here is hyperemic and is partially covered by a yellow-green exudate. The mucosa itself is not eroded. Broad spectrum antibiotic usage (such as clindamycin) and/or immunosuppression allows overgrowth of bacteria such as Clostridium dificile or S. aureus or fungi such as Candida to cause this appearance. The colonoscopic appearance is seen below.