Histology of pouch mucosa

(A) Normal pouch mucosa with tall villi and normal villus/crypt ratio. No inflammatory cell infiltration in the epithelium and lamina propria.
(B) Mild pouchitis with mainly chronic changes including crypt distortion, mononuclear cell infiltrations in the lamina propria and base of the crypts.
(C) Acute pouchitis with cryptitis and ulcers.
(D) Acute pouchitis with crypt abscess.