Are you seeing a gasteroenteroligist-specialist? "Active Chronic Colitis" means IBD...
This might interest you:
In early ulcerative colitis, the histopathology is characterized by epithelial necrosis, an acute inflammatory infiltrate in the lamina propria, cryptitis, and crypt abscesses. In chronic disease, a predominant lymphocytic infiltrate and distortion of crypt architecture are seen.
1.) acute inflammatory infiltrate in the lamina propria
3.) distortion of crypt architecture
Infectious-colitis is a one time infection that is cleared up with a single course of medications, and you do not have to worry about
it ever again. Ulcerative Colitis is a chronic, lifelong illness treated by medications. UC would show permanent changes under biopsy, and infectious-colitis does not. An example of permanent architectural changes is your "distortion of crypt architecture".