This is a reactive lesion seen in response to any agent that inflames or injures urothelial mucosa. The urothelial lining may form broad-based polypoid or slender papillary structures that may at first glance mimic urothelial neoplasia. In-dwelling catheters and colovesical fistulas are some of the common causes. This bladder biopsy shows several polypoid and papillary areas. The lamina propria contains dense inflammatory infiltrate.