Lesions tend to occur 4 to 18 cm from the anal margin and are usually located on the anterior rectal wall.
Lesions may include:
(1) inflammation of the rectal mucosa with induration, erythema and/or edema
(2) 0, 1 or multiple superficial mucosal ulcers
(3) 0, 1 or multiple polypoid lesions
Histologic features:
(1) smooth muscle proliferation that extends from the muscularis mucosae into the lamina propria
(2) fibrosis in the lamina propria
(3) distortion of the colonic crypts (elongation, hyperplasia, etc)
(4) variable hyperplasia of the surface epithelium which may be serrated, villiform or polypoid
(5) ectatic mucosal blood vessels
(6) variable mucosal erosions or ulcers, typically limited to the lamina propria
(7) variable presence of colitis cystica profunda (mucous glands misplaced into the submucosa)
(8) variable nonspecific subacute or chronic inflammation
